UBC Theses and Dissertations

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UBC Theses and Dissertations

Modelling issues in repetitive construction and an approach to schedule updating Williams, Rhys E. 1985

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MODELLING ISSUES IN REPETITIVE CONSTRUCTION AND AN APPROACH TO SCHEDULE UPDATING by RHYS E. WILLIAMS B . A . S c . , U n i v e r s i t y Of B r i t i s h Columbia,1983 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE i n THE FACULTY OF GRADUATE STUDIES Department Of C i v i l E n g i n e e r i n g We accept t h i s t h e s i s as con f o r m i n g t o the r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA J u l y 1985 © Rhys E. W i l l i a m s , 1985 I n p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the r e q u i r e m e n t s f o r an advanced degree a t the U n i v e r s i t y of B r i t i s h C o l umbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g of t h i s t h e s i s f o r s c h o l a r l y purposes may be g r a n t e d by the Head of my Department or by - h i s or her r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department of C i v i l E n g i n e e r i n g The U n i v e r s i t y of B r i t i s h Columbia 2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5 Date: J u l y 12,1985 i i ABSTRACT P l a n n i n g and c o n t r o l of time and o t h e r r e s o u r c e s are c r u c i a l t o the c o n s t r u c t i o n of l a r g e p r o j e c t s . Y e t , c u r r e n t c o m p u t e r i z e d t e c h n i q u e s are unable t o model the work p a t t e r n s by which c o n s t r u c t i o n p e r s o n n e l p l a n a p r o j e c t . F u r t h e r m o r e , these methods a r e not c a p a b l e of r e f l e c t i n g the day t o day changes which must be m o n i t o r e d t o c o n t r o l the c o n s t r u c t i o n s i t e . The purpose of t h i s t h e s i s - i s t o promote the u s e a b i l i t y of c o m p u t e r i z e d p l a n n i n g and s c h e d u l i n g through the development of the h e u r i s t i c manner by which c o n s t r u c t i o n p e r s o n n e l p e r c e i v e the p r o j e c t . S i t e s t u d i e s h e l d i n c o o p e r a t i o n w i t h Poole C o n s t r u c t i o n L i m i t e d and F o u n d a t i o n Company ' of Canada were performed u s i n g a computer s c h e d u l i n g system a t the U n i v e r s i t y of B r i t i s h Columbia which c o n t a i n e d a p r o t o t y p e model of r e p e t i t i v e work. I t p r o v i d e d i n s i g h t t o the p r o c e s s of r e p e t i t i o n and rhythm by which p r o j e c t s a r e p l a n n e d and t o the r e q u i r e m e n t s of the u p d a t i n g p r o c e s s n e c e s s s a r y t o m o n i t o r , and hence c o n t r o l t h e p r o j e c t . Two models e v o l v e d . The d e f i n i t i o n of the g e n e r a l r e p e t i t i v e s t r u c t u r e was f o r m u l a t e d t o p r o v i d e c o n s t r u c t i o n p e r s o n n e l w i t h a t o o l by which t o model the p r o c e s s of r e p e t i t i o n . The d e f i n i t i o n of an u p d a t i n g p r o c e s s was f o r m u l a t e d c a p a b l e of m o n i t o r n g d a i l y p r o g r e s s on a c o n s t r u c t i o n s i t e . Work performed w i t h t h e s e models have shown them t o be r e a l i s t i c i n t h e i r approach t o c o n s t r u c t i o n management. ACKNOWLEDGEMENT The r e s e a r c h c o n t a i n e d i n t h i s t h e s i s was made p o s s i b l e through f u n d i n g by the N a t u r a l S c i e n c e s and E n g i n e e r i n g Research C o u n c i l of Canada (NSERC). I w i s h t o e x p r e s s my g r a t i t u d e t o Dr. A l a n D. R u s s e l l , my s u p e r v i s o r , f o r h i s guidance and a d v i c e throughout the study. H i s e f f o r t i n r e v i e w i n g the t h e s i s and g i v i n g s u g g e s t i o n s t o improve i t s c o n t e n t a r e g r e a t l y a p p r e c i a t e d . I would l i k e t o thank Bob F r e n c h , P r o j e c t E n g i n e e r f o r Poole C o n s t r u c t i o n L i m i t e d , Frank Smith and D a v i d B e l l a m y , S i t e S u p e r v i s o r and P r o j e c t Manager r e s p e c t i v e l y f o r Fou n d a t i o n Company of Canada f o r t h e i r c o o p e r a t i o n and time g i v e n throughout the r e s e a r c h . F i n a l l y , I wi s h t o thank my f a m i l y and f r i e n d s f o r t h e i r encouragement and s u p p o r t . I am e s p e c i a l l y g r a t e f u l t o J e n n i f e r Anne Cook, my f r i e n d , f o r her time and e f f o r t g i v e n t h r o u g h o u t the t h e s i s . i v TABLE OF CONTENTS ABSTRACT i i ACKNOWLEDGEMENT i i i TABLE OF CONTENTS i v LIST OF FIGURES v i LIST OF TABLES v i i CHAPTER I ~ BACKGROUND 1.1 I n t r o d u c t i o n 1 1.2 T h e s i s O b j e c t i v e s 3 1.3 Methodology 4 1.4 T h e s i s Overview 5 CHAPTER I I - THE REPETITIVE ACTIVITY 2 .1 O b j e c t i v e s , 6 2.2 Laramee's Model 9 2.3 P r e v i o u s S t u d i e s 13 2.3.1 The S i t e S t u d i e s 16 2.4 O b s e r v a t i o n s 18 2.4.1 A) F l e x i b i l i t y 18 2.4.1.1 User I n t e r f a c e 21 2.4.2 B) L o g i c R e l a t i o n s h i p s 22 2.4.2.1 System Loops 24 2.4.3 C) C o n t i n u i t y 26 2.4.4 D) C r i t i c a l i t y 31 2.4.4.1 L o s s e s Due t o L i n e a r R e p e t i t i o n 34 2.5 The G e n e r a l R e p e t i t i v e S t r u c t u r e 37 2.5.1 A) Data S t r u c t u r e 40 2.5.2 B) F l e x i b i l i t y 46 2.5.3 C) C o n t i n u i t y 46 2.6 The R e p e t i t i v e B u i l d i n g P r o c e s s 48 2.6.1 The F l o w c h a r t 49 2.7 Summary 54 V CHAPTER I I I - CONTINUOUS UPDATING 3.1 I n t r o d u c t i o n 56 3.2 C r i t e r i a Used t o Promote The Use of U p d a t i n g 57 3.3 C r i t e r i o n 1: I n t e g r a t i o n i n t o the System 60 3.3.1 The Data Base C e n t r e 61 3.3.1.1 The Log 62 3.3.2 The Time C e n t r e 62 3.3.3 The Monetary C e n t r e 64 3.3.4 The D e c i s i o n Making P r o c e s s 65 3.3.5 L i t i g a t i o n Support 66 3.4 C r i t e r i o n 2: The U p d a t i n g P r o c e s s 69 3.4.1 Phase A 69 3.4.2 Phase B 71 3.4.3 Schedule I n t e r a c t i o n 72 3.5 C r i t e r i o n 3: Automation of the U p d a t i n g P r o c e s s 74 3.6 The Continuous U p d a t i n g A l g o r i t h m 76 3.6.1 The A c t i v i t y Window , 77 3.6.2 The A c t i v i t y D u r a t i o n s 78 3.6.3 The A c t i v i t y S t a r t s and F i n i s h e s 79 3.6.4 S u b s t a n t i a l C o m p l e t i o n vs T o t a l C o m p l e t i o n .... 80 3.6.5 Procurement 81 3.6.6 The H i e r a r c h i c a l S t r u c t u r e of L i n k s 82 3.6.7 The V a l i d i t y of L o g i c L i n k s 84 3.6.8 The Completed A c t i v i t y and i t s L o g i c L i n k s .... 86 3.6.9 The Scheduled A c t i v i t y and i t s L o g i c L i n k s .... 86 3.6.10 The Ongoing A c t i v i t y and i t s L o g i c L i n k s 90 3.6.11 Summary 92 3.7 U p d a t i n g the R e p e t i t i v e S t r u c t u r e 93 3.7.1 The Update B l o c k 94 3.7.2 Update C o n v e n t i o n f o r the R e p e t i t i v e A c t i v i t y . 96 3.8 The Computer Model 98 3.9 C o n c l u s i o n •. 99 CHAPTER IV - FURTHER ISSUES AND CONCLUSION 4.1 I n t r o d u c t i o n 100 4.2 The G e n e r a l i t y of R e p e t i t i v e Work 100 4.3 Computer Implementation and the C o n s t r u c t i o n I n d u s t r y 102 4.3.1 User I n t e r f a c e 104 4.4 Computers and Data S t o r a g e 105 4.5 E x p e r t Systems 107 4.6 Recommendations f o r F u t u r e Work 108 4.7 C o n c l u s i o n 110 BIBLIOGRAPHY 112 v i LIST OF FIGURES 2.1 Laramee's R e p e t i t i v e S t r u c t u r e 11 2.2 R e p e t i t i v e S t r u c t u r e w i t h M u l t i p l e Crews 11 2.3 The T y p i c a l L i n k 12 2.4 N o n - T y p i c a l L i n k s 13 2.5 F i n i s h e d Schedule 14 2.6 M o d e l l i n g Changes i n Number of Crews by V a r y i n g P r o d u c t i o n Rate 19 2.7 Examples of G r a p h i c Output of the R e p e t i t i v e S t r u c t u r e 22 2.8 Resequencing and N o n - T y p i c a l L o g i c C o n s t r a i n t s 23 2.9 Resequencing and T y p i c a l L o g i c C o n t r a i n t s 24 2.10 A L o g i c Loop I n v o l v i n g a R e p e t i t i v e A c t i v i t y 25 2.11 C o n t i n u i t y of I n t e r n a l Rhythm 28 2.12 C o n t i n u i t y of E x t e r n a l Rhythm 29 2.13 C o n t i n u i t y Imposing C r i t i c a l i t y 32 2.14 C o n t i n u i t y and I t s Use of F l o a t 33 2.15 Worst and Best Case Models of L i n e a r R e p e t i t i o n 35 2.16 Examples Based on the G e n e r a l R e p e t i t i v e A c t i v i t y D e f i n i t i o n 42 2.17 The S e q u e n t i a l F i l e INPUT 43 2.18 T r a d e o f f Between G e n e r a l i t y of R e p e t i t i v e A c t i v i t y D e f i n i t i o n and E f f i c i e n c y of Data Input 45 2.19 The Use of P o o l s i n the S i m u l a t i o n P r o c e s s 50 2.20 The S e q u e n t i a l F i l e OUTPUT 51 2.21 F l o w c h a r t of the R e p e t i t i v e A c t i v i t y B u i l d i n g P r o c e s s 52 2.22 F i n i s h e d Model of the R e p e t i t i v e A c t i v i t y 55 3.1 S i m p l i f i e d . C o n s t r u c t i o n Management I n f o r m a t i o n System 60 3.2 The U p d a t i n g P r o c e s s F l o w c h a r t 70 3.3 The A c t i v i t y Window and I t s L o g i c L i n k s 77 3.4 Three Types of A c t i v i t i e s and T h e i r D u r a t i o n s 78 3.5 S t a r t and F i n i s h D e f i n i t i o n s and T h e i r Time Zones ... 79 3.6 Example of C o n t s r a i n t M o d e l l e d as a L o g i c L i n k 84 3.7 Forward and Backward Pass of a Scheduled A c t i v i t y ... 87 3.8 I n v a l i d a t i o n of S u c c e s s o r L i n k s w i t h an A c t u a l S t a r t Date 88 3.9 I n v a l i d a t i o n of S u c c e s s o r L i n k s w i t h an A c t u a l F i n i s h Date 89 3.10 Forward and Backward Pass of the Ongoing A c t i v i t y ... 91 3.11 The R e p e t i t i v e A c t i v i t y Update F l o w c h a r t 95 3.12 Example of an Updated R e p e t i t i v e A c t i v i t y 98 v i i LIST OF TABLES 3.1 The Four S e t s of Data R e q u i r e d f o r U p d a t i n g 82 3.2 The H i e r a r c h i c a l S t r u c t u r e of L i n k s 83 1 CHAPTER I BACKGROUND 1 . 1 I n t r o d u c t i o n The key focus of t h i s t h e s i s i s t o promote t h e u s e a b i l i t y of c o m p u t e r i z e d p l a n n i n g and s c h e d u l i n g i n the c o n s t r u c t i o n i n d u s t r y . T h i s i s a c h i e v e d by expanding s c h e d u l i n g t h e o r y t o model the p r o c e s s of r e p e t i t i o n and rhythm found on the c o n s t r u c t i o n s i t e t h r ough the d e f i n i t i o n of a g e n e r a l r e p e t i t i v e a c t i v i t y s t r u c t u r e . I t i s f u r t h e r a c h i e v e d by d e f i n i n g a u s e a b l e u p d a t i n g p r o c e s s t h a t a u t o m a t i c a l l y updates the network based on i n p u t s t y p i c a l l y c o l l e c t e d on d a i l y p r o g r e s s r e p o r t s . C o n s t r u c t i o n p r o j e c t s c o n s i s t of hundreds, and o f t e n thousands of a c t i v i t i e s which must be c o o r d i n a t e d and c o n t r o l l e d t o produce a s u c c e s s f u l p r o j e c t c o m p l e t i o n . Such l a r g e volumes of data cannot be m a i n t a i n e d by the human mind. There i s a s t r o n g need f o r c o m p u t e r i z a t i o n t o p e r f o r m c a l c u l a t i o n s q u i c k l y and c o n c i s e l y . The advent of Program E v a l u a t i o n Review Technique (PERT) and C r i t i c a l P a t h Methods (CPM) i n the l a t e 1950's brought the problems of s c h e d u l i n g l a r g e p r o j e c t s t o the s u r f a c e . CPM p r o v i d e d an avenue by which a c t i v i t i e s c o u l d be sc h e d u l e d based on a s e t of l o g i c s u p p l i e d by the u s e r . The computer c o u l d then produce a sc h e d u l e by which the p r o j e c t c o u l d be b u i l t . W h i l e s i g n i f i c a n t d e t a i l was r e q u i r e d of the 2 u s e r , the c a l c u l a t i o n s of the s c h e d u l e c o u l d be p e r f o r m e d swi f t l y . C o n s t r u c t i o n f i r m s would compute the CPM s c h e d u l e and b e g i n the p r o j e c t o n l y t o f i n d t h a t work p r o g r e s s d i d not a l w a y s f o l l o w the s c h e d u l e . There was a need t o a d j u s t the s c h e d u l e t o r e f l e c t the p r o j e c t advancement and p r o v i d e an updated s c h e d u l e f o r the r e m a i n i n g a c t i v i t i e s . T h i s o f t e n i n v o l v e d r e v i e w i n g a l l l o g i c of the network t h a t was not r e a l i z e d on the p r o j e c t . T h i s p roved t o be a v e r y d i f f i c u l t and time consuming t a s k f o r the u s e r . F u r t h e r , f o r r e p e t i t i v e t y p e s of c o n s t r u c t i o n (eg. b r i d g e s , h i g h - r i s e s , e t c . ) the c o n s t r u c t i o n i n d u s t r y was a l s o hampered by d a t a which had t o be e n t e r e d on an a c t i v i t y by a c t i v i t y b a s i s ( l o w - l e v e l d a t a ) . S i t e w o r k f o r such p r o j e c t t y p e s i s o f t e n paced by g r o u p i n g a c t i v i t i e s i n t o p r o d u c t i o n l i n e s . The p r o j e c t i s o f t e n p e r c e i v e d as l a r g e b l o c k s of d a t a and not on a s i n g l e a c t i v i t y b a s i s . I t proved t o be v e r y d i f f i c u l t t o e n t e r enough d a t a t o r e p r e s e n t such g r o u p i n g s on CPM or PERT. C o n v e n t i o n a l s c h e d u l i n g of l a r g e p r o j e c t t y p e s has not been w e l l r e c e i v e d by the c o n s t r u c t i o n i n d u s t r y . Two i m p o r t a n t reasons a r e : A) S c h e d ules a r e not c a p a b l e of u p d a t i n g t o p r o j e c t c o n d i t i o n s q u i c k l y enough t o h e l p i n c r i t i c a l d e c i s i o n a n a l y s i s . 3 B) Data g r o u p i n g i s d i f f i c u l t and time consuming t o model on the a c t i v i t y by a c t i v i t y b a s i s of c u r r e n t network models. 1.2 T h e s i s O b j e c t i v e s The i d e a of h i g h e r - l e v e l i n p u t s has been a d d r e s s e d by Laramee ( R e f e r e n c e 16) who devel o p e d a d e f i n i t i o n of a r e p e t i t i v e a c t i v i t y which c o n s i s t e d of t y p i c a l a c t i v i t i e s p e r f o r med a t numerous l o c a t i o n s on s i t e . W h i l e the a l g o r i t h m d i d a l l o w some advantages of c o n t i n u i t y of work and rhythm, i t was l i m i t e d i n i t s a b i l i t y t o model the c o n s t r u c t i o n s i t e and d i d not a l l o w f o r a r b i t r a r y sequence changes when u p d a t i n g . The o b j e c t i v e s of t h i s t h e s i s a re t w o f o l d . F i r s t , t o use Laramee's p r o t o t y p e model as a base by which t o study the r e p e t i t i v e n a t u r e of c o n s t r u c t i o n through an i n depth s i t e s tudy and d e v e l o p the r e p e t i t i v e a c t i v i t y i n t o a g e n e r a l i z e d h i g h e r l e v e l s t r u c t u r e . Second, t o f u r t h e r use the o p p o r t u n i t y of the s i t e s tudy t o d e f i n e an u p d a t i n g p r o c e s s f o r the c o n s t r u c t i o n i n d u s t r y , i n c l u d i n g an a l g o r i t h m f o r the a u t o m a t i c u p d a t i n g of the s c h e d u l e thus e l i m i n a t i n g the need f o r the user t o c o n s t a n t l y mould the network l o g i c t o f i t a c t u a l p r o g r e s s . 4 1.3 Methodology The t h e s i s o r i g i n a t e d w i t h an e x t e n s i v e s e a r c h of l i t e r a t u r e . T h i s was f o l l o w e d by a l i m i t e d e x a m i n a t i o n of a $30 m i l l i o n , 26 s t o r e y h i g h - r i s e p r o j e c t . I t became e v i d e n t t h a t the r e p e t i t i v e a c t i v i t y c o u l d be c l e a r l y d e f i n e d . I t was a l s o c l e a r t h a t c o n t i n u o u s u p d a t i n g of the s c h e d u l e was e s s e n t i a l i f s c h e d u l i n g was t o be a u s e f u l c o n s t r u c t i o n management t o o l . The r e q u i r e m e n t s of the' u p d a t i n g p r o c e s s were d e f i n e d . A p r o t o t y p e system c o n t a i n i n g the a u t o m a t i c u p d a t i n g a b i l i t y was added t o a s c h e d u l i n g package c o n t a i n i n g Laramee's r e p e t i t i v e d e f i n i t i o n . The system was t e s t e d e x t e n s i v e l y on a $5 m i l l i o n , 4 s t o r e y c ommercial b u i l d i n g . The t e s t p r o j e c t i n v o l v e d s u b s t a n t i a l i n t e r a c t i o n w i t h the s i t e s u p e r i n t e n d e n t and r e g u l a r c o n t a c t w i t h the p r o j e c t manager. S u g g e s t i o n s from management were i n c o r p o r a t e d w i t h t e s t r e s u l t s t o mould the system i n t o i t s f i n a l s t a t e . The r e q u i r e m e n t s of the r e p e t i t i v e a c t i v i t y e v o l v e d t h roughout the e x t e n s i v e t e s t i n g of the system. S y s t e m a t i c u p d a t i n g of the p r o j e c t , made p o s s i b l e by the newly added u p d a t i n g p r o c e s s , p r o v i d e d i n s i g h t i n t o the e f f e c t s of c o n t i n u i t y , f l o a t and c r i t i c a l i t y of the r e p e t i t i v e - s t r u c t u r e . A g e n e r a l s t r u c t u r e was then d e f i n e d f o r the r e p e t i t i v e a c t i v i t y t o be added t o the u p d a t i n g d e f i n i t i o n and complete the model. Of prime importance was a model which was s i m p l e t o use and 5 of an a c c e p t a b l e format t o the c o n s t r u c t i o n i n d u s t r y . T h i s e n t a i l e d c a p t u r i n g the n o t i o n of u p d a t i n g and r e p e t i t i o n i n the manner i n which i t i s p e r c e i v e d by the c o n s t u c t i o n p e r s o n n e l . F u r t h e r m o r e , i t had t o be p r e s e n t e d i n a way t h a t p e r s o n n e l c o u l d q u i c k l y g r a s p and thus promote i t s use. The model aimed a t m i n i m a l i n p u t s by the user and promoted an e f f i c i e n t u s e r i n t e r f a c e . 1.4 T h e s i s Overview Chapter I I d e f i n e s the concept of the r e p e t i t i v e a c t i v i t y and o u t l i n e s the c h a r a c t e r i s t i c s by which the c o n s t r u c t i o n i n d u s t r y p e r c e i v e s i t s r o l e i n p r o v i d i n g c o n t i n u i t y and rhythm t o the p r o j e c t . The f i n a l d e f i n i t i o n i s i n c l u d e d a t the end of the c h a p t e r . Chapter I I I d e f i n e s the c o n s t r u c t i o n i n d u s t r y ' s view of u p d a t i n g and s u g g e s t s a p r o c e s s by which c o n t i n u o u s m o n i t o r i n g of the s c h e d u l e may be a t t a i n e d . The c o n t i n u o u s u p d a t i n g a l g o r i t h m i s i n c l u d e d a t the end of the c h a p t e r a l o n g w i t h i t s h a n d l i n g of the r e p e t i t i v e a c t i v i t y d e s c r i b e d i n Chapter I I . Chapter IV d i s c u s s e s i s s u e s which a r o s e from work i n the a r e a s of d a t a s t o r a g e , e x p e r t systems and i t s communication t o the c o n s t r u c t i o n i n d u s t r y . The c h a p t e r c l o s e s w i t h recommendations f o r f u t u r e work and the c o n c l u s i o n t o t h i s t h e s i s. 6 CHAPTER I I THE REPETITIVE ACTIVITY 2.1 O b j e c t i v e s The purpose of t h i s c h a p t e r i s t o d e v e l o p a t e c h n i q u e by which t o c a p t u r e the i n h e r e n t p r o c e s s of l i n e a r r e p e t i t i o n e v i d e n t i n h i g h - r i s e and o t h e r forms of l i n e a r c o n s t r u c t i o n i n t o a c o m p u t e r i z e d s c h e d u l i n g a l g o r i t h m . T h i s p r o c e s s w i l l e nable c o n c u r r e n t m a n i p u l a t i o n of l a r g e b l o c k s of d a t a g i v i n g the user a p o w e r f u l s c h e d u l i n g a b i l i t y t o model work p a t t e r n s and the i n t r i n s i c rhythm which they p r o v i d e t o the p r o j e c t . S c h e d u l i n g a c o n s t r u c t i o n p r o j e c t r e q u i r e s the d e f i n i t i o n of each a c t i v i t y and a r e a l i z a t i o n of how i t f i t s i n t o the o v e r a l l p r o c e s s . T h i s l e v e l of d e t a i l g e n e r a t e s a s u b s t a n t i a l amount of da t a which must be c o m p i l e d i f an a c c u r a t e model i s t o be a t t a i n e d . W h i l e the d a t a cannot be s i g n i f i c a n t l y d e c r e a s e d w i t h o u t l o s i n g m o d e l l i n g c a p a b i l i t y , i t i s p o s s i b l e t o r e d e f i n e i n p u t s so t h a t much of the data i n p u t can be c a l c u l a t e d a u t o m a t i c a l l y and i n a way t h a t r e f l e c t s work c o n t i n u i t y p a t t e r n s d e s i r e d by c o n s t r u c t i o n p e r s o n n e l . The above premise i s based on d e f i n i n g i n h e r e n t s t r u c t u r e s i n the c o n s t r u c t i o n p r o c e s s which enable d a t a t o be d e s c r i b e d a t a h i g h e r l e v e l and then g e n e r a t e the lower l e v e l i n f o r m a t i o n ; 7 much l i k e the word " a l p h a b e t " which g e n e r a t e s the sequence "ABCD....to Z", e l i m i n a t i n g s u b s t a n t i a l d a t a i n p u t , y e t r e t a i n i n g a l l e s s e n t i a l d e t a i l s of the d a t a base. These s t r u c t u r e s a r e known as h i g h e r l e v e l i n f o r m a t i o n o b j e c t s : h i g h l e v e l d a t a c a p a b l e of b r e a k i n g down t o a f u l l low l e v e l base. A paper by Anderson, F j o s n e and S o l b e r g (Reference 1) showed t h i s methodology c o u l d s u b s t a n t i a l l y reduce the i n p u t s r e q u i r e d f o r the model. Thus the a l g o r i t h m o f f e r s o p t i m i z a t i o n of data i n p u t and the a b i l i t y t o model the i n h e r e n t p r o c e s s by which l a r g e p r o j e c t s a r e c o n t r o l l e d . L i t e r a t u r e ( R e f e r e n c e s 6,15,20 and 28) shows the a r e a of l i n e a r r e p e t i t i o n t o be one of g r e a t p o t e n t i a l t o c a p t u r e the h e u r i s t i c n a t u r e of the c o n s t r u c t i o n p r o c e s s and b e n e f i t from i t s i n c r e a s e d c o o r d i n a t i o n , l e a r n i n g e f f e c t s , and r e s o u r c e h a n d l i n g . I t s n a t u r a l g r o u p i n g of low l e v e l d a t a makes i t a prime a r e a f o r the a d o p t i o n of h i g h e r l e v e l s t r u c t u r e s . The r e p e t i t i v e s t r u c t u r e i s t y p i c a l l y found on l a r g e r e p e t i t i v e t y pe p r o j e c t s such as h i g h - r i s e s , roadways, and p i p e l i n e s , which a r e c o n d u c i v e t o r h y t h m i c p r o g r e s s i o n of work packages a l o n g a s e r i e s of l o c a t i o n s . O 'Brien ( R e f e r e n c e 19) r e c o g n i z e d the h y b r i d of r e p e t i t i v e and n o n - r e p e t i t i v e a c t i v i t i e s p r e s e n t i n the c o n s t r u c t i o n of h i g h - r i s e b u i l d i n g s and c l a s s i f i e d them as two d i s t i n c t modes of c o n s t r u c t i o n . S t r a d a l and Cacha. (Reference 29) d e f i n e d t h r e e c l a s s e s of r e p e t i t i v e work sequences which they f e l t t o be noteworthy f a c t o r s t o c o n s i d e r d u r i n g s c h e d u l i n g . These 8 sequences were based on the sense of rhythm which they brought t o the p r o j e c t . Peer ( R e f e r e n c e 22) noted t h a t m a n u f a c t u r e r s o f t e n used r e p e t i t i o n as a t o o l t o o p t i m i z e the p r o d u c t i v i t y of t h e i r machine shops. He l i k e n e d r e p e t i t i v e work of h i g h - r i s e c o n s t r u c t i o n t o a m a n u f a c t u r i n g p r o c e s s , d e f i n i n g a system where s i n g l e and r e p e t i t i v e a c t i v i t i e s c o u l d be amalgamated i n t o one system t o ta k e advantage of h i g h e r p r o d u c t i v i t y t h r o u g h c o n t i n u i t y of work. He a l s o s t a t e d the i n s u f f i c i e n t e x p l o r a t i o n of t h i s s t r u c t u r e i n s c h e d u l i n g t h e o r y : "The need f o r c r e a t i n g working c o n t i n u i t y and b a l a n c i n g the whole p r o c e s s i n t o an i n t e g r a t e d p r o d u c t i o n system i s c o m p l e t e l y , n e g l e c t e d . " . The s t r o n g e s t statement came from B i r r e l l (Reference 3) who was k e e n l y aware of h e u r i s t i c s t r u c t u r e s of the c o n s t r u c t i o n i n d u s t r y and was not c o n v i n c e d t h a t c u r r e n t s c h e d u l i n g a b i l i t i e s were s u f f i c i e n t : "There have been v a r i o u s p r e s e n t a t i o n s of networks f o r v a r i o u s u s e s , and the c o n s t r u c t i o n i n d u s t r y has t r i e d t o use the CPM and PERT v a r i a t i o n s w i t h u n s a t i s f a c t o r y r e s u l t s m a i n l y due t o t h e i r i n c o m p a t i b i l i t y t o the essence of the c o n s t r u c t i o n p r o c e s s . " He s t r e s s e d the need t o t a p the e x p e r i e n c e of the management p e r s o n n e l the h e u r i s t i c concept of c o n s t r u c t i o n s c h e d u l i n g : " T h i s h e u r i s t i c concept of t h e c o n s t r u c t i o n p r o c e s s i s a model t h a t i s s i m p l e , s t r o n g , r e a l i s t i c , o p t i m a l l y cheap t o use, but u n f o r t u n a t e l y not w r i t t e n down. I t i s o n l y r e a l i z e d by those people who a r e , or have been, i n v o l v e d i n a c t u a l c o n s t r u c t i o n management. S e n i o r c o n s t r u c t i o n p r a c t i t i o n e r s who have put i n t o 9 w r i t i n g t h e i r t h o u g h t s on the matter r e a c h c o n c l u s i o n s s i m i l a r t o the above p a r a p h r a s e and t h e i r p r e s t i g e adds weight t o the c o n c e p t . " He a l s o surmised t h a t a r e a l i s t i c model i s based on o r g a n i z i n g the p r o j e c t i n t o s m a l l e r d e f i n a b l e "work squads" which w i l l pass t h r o u g h the l o c a t i o n s i n a s e t sequence; the n e c e s s a r y i n f o r m a t i o n t o a c h i e v e t h i s b e i n g a fundamental knowledge of c o n s t r u c t i o n t e c h n o l o g y and i t s i n d u s t r i a l o r g a n i z a t i o n . B i r e l l showed a s t r o n g l e a n i n g towards the r e p e t i t i v e p r o c e s s concept b u i l t upon the s p e c i f i c t e c h n o l o g i c a l and o r g a n i z a t i o n a l environment of each p r o j e c t . The l i t e r a t u r e shows l i n e a r r e p e t i t i o n t o be an im p o r t a n t ye t not f u l l y u n d e r s t o o d a s p e c t of s c h e d u l i n g . The g o a l of t h i s c h a p t e r i s t h e r e f o r e t o f u l l y r e a l i z e and d e v e l o p the l i n e a r r e p e t i t i v e p r o c e s s by a t t a i n i n g h i g h e r l e v e l i n f o r m a t i o n o b j e c t s which c a p t u r e the esence of work c o n t i n u i t y and rhythm found on the c o n s t r u c t i o n s i t e . 2.2 Laramee's Model. Laramee (Reference 16) d e v e l o p e d a w o r k i n g model t o show how the r e p e t i t i v e n a t u r e of h i g h - r i s e c o n s t r u c t i o n c o u l d be m o d e l l e d t o take advantage of c o n t i n u i t y of work and y e t not l o s e s i g h t of the i n d i v i d u a l a c t i v i t y d e f i n i t i o n . T h i s was a c h i e v e d by the d e f i n i t i o n of a r e p e t i t i v e s t r u c t u r e -an a c t i v i t y which i s r e p e a t e d a t s e v e r a l l o c a t i o n s i n space i n a l i n e a r p r o g r e s s i o n of t i n r e - m o d e l l e d w i t h h i g h l e v e l d a t a . T h i s 10 d a t a i s then used t o generate the low l e v e l d a t a n e c e s s a r y t o complete the d a t a base. The h i g h l e v e l d a t a r e q u i r e d t o generate the r e p e t i t i v e s t r u c t u r e c o n s i s t s o f : a) a c t i v i t y name, code number and g e n e r a l f a c t o r s b) s t a r t i n g l o c a t i o n c) e n d i n g l o c a t i o n d) number of crews e) p r o d u c t i o n r a t e s of each l o c a t i o n f ) s t a r t t o s t a r t time g) f i n i s h t o s t a r t time The d a t a of a) r e p r e s e n t s the p r i m a r y l i n k s t o t h e u s e r , the d a t a base, and e x t e r n a l c o n s t r a i n t s of the a c t i v i t y such as weather f a c t o r s and l e a r n i n g c u r v e s . The d a t a of b) t o g) g e n e r a t e s the a c t i v i t y shown i n F i g u r e 2.1. A l l l o c a t i o n s between l e v e l 3 and l e v e l 6 a r e a u t o m a t i c a l l y i n c l u d e d : a premise of Laramee's model. The p r o d u c t i o n r a t e i s 4 d a y s / l e v e l . The f i n i s h t o s t a r t (FS) l i n k between the l e v e l s of a p a r t i c u l a r crew (eg. FS=1) models the time r e q u i r e d f o r s e t u p and m a t e r i a l h a n d l i n g . I f more than one crew i s s p e c i f i e d (eg. crews=2), a s t a r t t o s t a r t (SS) l i n k between crews i s p e r m i t t e d t o model s h a r i n g of r e s o u r c e s between crews (eg. SS=2, F i g u r e 2.2). These l i n k s (FS, SS) j o i n l e v e l s w i t h i n t h e r e p e t i t i v e s t r u c t u r e and a r e r e f e r r e d t o as i t s i n t e r n a l l o g i c . 11 6 FS=1 r 5 FS=1 r 4 FS=1 3 5 1 0 DAYS 1 5 B=3 C=6 D = 1 E=4 F = N / A G=1 2 0 F i g u r e 2.1 Laramee's R e p e t i t i v e S t r u c t u r e < u S 4 c r e w 2 c r e w l BETVf S :EN CRE 5=2 1 » V S c r e w 2 s FS=1 *ME Cfi L . EV 1 c rew 1 ....... J 4 6 DAYS 8 1 0 B=3 C=6 D=2 E=4 F = 2 G=1 F i g u r e 2.2 R e p e t i t i v e S t r u c t u r e w i t h M u l t i p l e Crews As the model c o n s i s t s of a h y b r i d s c h e d u l e of r e p e t i t i v e and n o n - r e p e t i t i v e a c t i v i t i e s , two l o g i c l i n k s a r e needed. a) t y p i c a l l i n k 1 2 b) n o n - t y p i c a l l i n k These l i n k s i n t e r r e l a t e the h i g h and low l e v e l s t r u c t u r e s and a r e r e f e r r e d t o as the e x t e r n a l l o g i c . The t y p i c a l l i n k i s used t o r e p r e s e n t a r e l a t i o n s h i p between the same l e v e l s of two r e p e t i t i v e a c t i v i t i e s ( F i g u r e 2.3). T h i s l i n k i s commonplace d u r i n g many phases of c o n s t r u c t i o n where one work package f o l l o w s the next (eg. b u i l d form, p l a c e r e b a r , pour c o n c r e t e . . . ) . The n o n - t y p i c a l l i n k i s F i g u r e 2.3 The T y p i c a l L i n k used t o r e p r e s e n t a l l o t h e r r e l a t i o n s h i p s ( F i g u r e 2.4). T h i s l i n k i s e s s e n t i a l t o amalgamating a h y b r i d system and e n s u r i n g a complete l o g i c network. The Forward and Backward Pass r e q u i r e d t o ge n e r a t e the sc h e d u l e a r e performed on a time-space m a t r i x . B l o c k s of da t a 1 3 Repe t i t i v e to Repe t i t i v e Repe t i t i ve to Non-Repet i t i ve Non -Repe t i t i v e to Non -Repe t i t i v e < U o 3 1 1 Blllllllllllllltl / \ / S D A Y S F i g u r e 2.4 N o n - T y p i c a l L i n k s are moved i'n a c e r t a i n d i r e c t i o n ( i . e . a l o n g the time a x i s ) but m a i n t a i n t h e i r a l l o c a t i o n i n space. D u r i n g each pass, the r e p e t i t i v e a c t i v i t y i s moved as a b l o c k of data t o m a i n t a i n i t s r e l a t i v e s t r u c t u r e on the m a t r i x . Thus, the p r o c e s s ensures c o o r d i n a t i o n of a l l a c t i v i t i e s w i t h i n the c o n s t r a i n t s of time and space and a t the same time a l l o w s c o n t i n u i t y of r e p e t i t i v e s t r u c t u r e s ( F i g u r e 2.5). 2.3 P r e v i o u s S t u d i e s Laramee 1s model s u r p a s s e d t h a t of B i r r e l l by d e f i n i n g the b a s i c r e q u i r e m e n t s of a r e p e t i t i v e a c t i v i t y and implementing them i n t o a working system. E a r l y s i t e s t u d i e s showed the d e f i n i t i o n t o be p o w e r f u l i n i t s a b i l i t y t o model i n l a r g e b l o c k s of d a t a , but l i m i t e d i n i t s a p p l i c a t i o n . 14 MOTE A L L L I N K S A R E F S = 0 o DAYS F i g u r e 2.5 F i n i s h e d Schedule When P r o f e s s o r A.D. R u s s e l l r e l o c a t e d t o the U n i v e r s i t y of B r i t i s h Columbia from C o n c o r d i a U n i v e r s i t y , two e x t e n s i o n s were added t o Laramee's model (Re f e r e n c e 2 6 ) : A) The a b i l i t y t o o v e r l a p a c t i v i t i e s u s i n g l a g s o t h e r than FS=0 (SS, SF, FS, FF) was added. T h i s a l l o w e d a c e r t a i n i n c r e a s e d f l e x i b i l i t y of b a s i c l o g i c l i n k s . B) A s t a g i n g e f f e c t was added t o d i v i d e the r e p e t i t i v e a c t i v i t y i n t o segments, where each segment c o u l d have i t s own p r o d u c t i o n r a t e . T h i s a l l o w e d i n c r e a s e d f l e x i b i l i t y of the work p r o f i l e . The a u t h o r worked w i t h t h i s r e v i s e d system and found the r e p e t i t i v e a s p e c t c o u l d o n l y model a s e l e c t group of 15 c o n s t r u c t i o n work p a t t e r n s . F u r t h e r m o r e , the model was f r a g i l e and c o u l d not take any m o d i f i c a t i o n d u r i n g the cou r s e of a p r o j e c t . T h i s was due t o the b a s i c d e f i n i t i o n of the data s t r u c t u r e by which r e p e t i t i o n was b u i l t . Much of the s t r u c t u r e i n c l u d e d l o g i c l i n k s t h a t were " i m p l i e d " by i t s g e o m e t r i c shape. However, u p d a t i n g the sc h e d u l e d i s t u r b e d the shape and i m p l i e d l i n k s were l o s t , e l i m i n a t i n g the a b i l i t y t o d e f i n e the r e p e t i t i v e a c t i v i t y as low l e v e l d a t a , and hence no l o n g e r c o n f o r m i n g t o the d e f i n i t i o n of h i g h e r l e v e l i n f o r m a t i o n o b j e c t s . Two p o i n t s were c l e a r : A) The r e p e t i t i v e a c t i v i t y as d e f i n e d by Laramee d i d not p r o v i d e a g e n e r a l i z e d d e f i n i t i o n by which t o c a p t u r e r e c o g n i z e d work p a t t e r n s i n c o n s t r u c t i o n . B) The r e p e t i t i v e a c t i v i t y was not a b l e t o m a i n t a i n i t s h i g h e r l e v e l s t r u c t u r e when s u b j e c t e d t o a r b i t r a r y changes t o t h e s e work p a t t e r n s . The aut h o r g e n e r a l i z e d the r e p e t i t i v e a c t i v i t y s t r u c t u r e by u n d e r t a k i n g a s p e c i f i c s i t e study u s i n g the r e v i s e d Laramee model combined w i t h the u p d a t i n g p r o c e s s d e s c r i b e d i n Chapter I I I . The work i n v o l v e d c l o s e i n t e r a c t i o n w i t h c o n s t r u c t i o n p e r s o n n e l t o g e n e r a t e feedback from a l l hy p o t h e s e s . The f o l l o w i n g s e c t i o n s d i s c u s s o b s e r v a t i o n s from the r e s e a r c h . 16 2.3.1 The S i t e S t u d i e s S t u d i e s used i n the r e s e a r c h i n c l u d e : c o n s t r u c t i o n of a s e c t i o n of the Advanced L i g h t R a p i d T r a n s i t (ALRT) p r o j e c t i n Vancouver, B r i t i s h Columbia; the Olympic O v a l f o r the 1988 W inter Olympic Games i n C a l g a r y , A l b e r t a ; and a 26 s t o r e y h i g h -r i s e i n downtown Vancouver. In a d d i t i o n , a l o n g term s i t e s tudy was r e q u i r e d t o a l l o w a thorough t r i a l of p r o t o t y p e r e p e t i t i v e s t r u c t u r e s . Most imp o r t a n t was the need t o f i n d a s i t e which c o u l d be m o d e l l e d throughout a l l phases of the p r o j e c t so t h a t a l l a s p e c t s of the a c t i v i t y c o u l d be e x p l o r e d . T h i s i n c l u d e d : e a r l y s c h e d u l i n g , f i x i n g s t a r t d a t e s , r e d e f i n i t i o n of a c t i v i t i t e s and t h e i r r e l a t i o n s h i p s , ongoing a c t i v i t i e s , u p d a t i n g e f f e c t s and f i n a l p r e s e n t a t i o n of the a s - b u i l t s c h e d u l e . The d e s i r e d study was a medium s i z e (5-10 m i l l i o n d o l l a r s ) p r o j e c t c o n s i s t i n g of s i g n i f i c a n t r e p e t i t i v e work t o j u s t i f y u s i n g the model, ye t s m a l l enough t o p e r m i t a h i g h ongoing v a r i a n c e i n c o n s t r u c t i o n m e t h o d o l o g i e s , a l l o w i n g c o n t i n u a l r e d e f i n i t i o n of the r e p e t i t i v e p r o c e d u r e s t o t e s t the model's f l e x i b i l i t y . The l o n g term s i t e study was performed on a $5 m i l l i o n commercial b u i l d i n g l o c a t e d i n the K i t s i l a n o a r e a of Vancouver. The p r o j e c t had 6 l e v e l s which c o u l d be m o d e l l e d as a r e p e t i t i v e a c t i v i t y . The G e n e r a l C o n t r a c t o r , F o u n d a t i o n Company of Canada began e x c a v a t i o n i n J a n uary 1984 and planned t o f i n i s h the p r o j e c t a t the end of J a n uary 1985. The s i t e s tudy was 1 7 implemented i n March 1984 and c o n t i n u e d u n t i l c o n s t r u c t i o n c o m p l e t i o n i n March 1985. A s c h e d u l e was developed and updated on a r e g u l a r b a s i s t h r o u g h c o o r d i n a t i o n of the S i t e S u p e r i n t e n d e n t , Frank Smith; an i n t e r n a t i o n a l l y e x p e r i e n c e d member of the company . Throughout the s t u d y , new t e c h n i q u e s were t e s t e d t o promote the u s e a b i l i t y of a computer generated s c h e d u l i n g system on a c o n s t r u c t i o n s i t e . 18 2.4 O b s e r v a t i o n s The a t t r i b u t e s of a r e p e t i t i v e a c t i v i t y can be grouped i n t o f o u r c a t e g o r i e s : A) F l e x i b i l i t y : degree t o which i t can be m o d e l l e d B) L o g i c R e l a t i o n s h i p s : i t s t i e s t o o t h e r a c t i v i t i e s C) C o n t i n u i t y : i t s c o n t r i b u t i o n t o p r o j e c t rhythm D) C r i t i c a l i t y : i t s e f f e c t on the use of f l o a t A d i s c u s s i o n of each c a t e g o r y and i t s e f f e c t on the s c h e d u l e i s g i v e n below. 2.4.1 A) F l e x i b i l i t y Laramee's d e f i n i t i o n p e r m i t s the m o d e l l i n g of a c t i v i t i e s as r e p e t i t i v e i f they are j o i n e d i n s e q u e n t i a l f l o o r s , p o r t r a y i n g a r e g u l a r rhythm on c o n s e c u t i v e l o c a t i o n s of a p r o j e c t . M o d e l l i n g of the ALRT p r o j e c t showed a f u r t h e r a p p l i c a t i o n of rhythm. Two d i f f i c u l t i e s were e n c o u n t e r e d u s i n g Laramee's o r i g i n a l model. F i r s t , because of d e s i g n c o n s i d e r a t i o n s not a l l a c t i v i t i e s were p r e s e n t a t each l o c a t i o n . In p a r t i c u l a r , c r o s s h e a d s were r e p e a t e d on a n o n - r e g u l a r b a s i s . T h i s n e c e s s i t a t e d t h e i r t r e a tment as n o n - r e p e t i t i v e low l e v e l a c t i v i t i e s . 19 Second, a c t i v i t i e s o f t e n r e q u i r e d changes i n the number of crews i n o r d e r t o meet c l i e n t imposed m i l e s t o n e s . As Laramee's model d i d not a l l o w changes i n t h e number of crews f o r the a c t i v i t y , i t was m o d e l l e d by changing t h e p r o d u c t i o n r a t e . For example, i f the number of crews was doubled f o r a p a r t i c u l a r s t a ge of the a c t i v i t y , the p r o d u c t i o n was doubled. However, t h i s was found t o g i v e an i n a c c u r a t e s c h e d u l e a t the low l e v e l d a ta as the s t a r t and f i n i s h of each l e v e l were not c o r r e c t (see F i g u r e 2.6). C o n s e q u e n t l y , the p r o j e c t ended up b e i n g broken i n t o f i v e phases w i t h work c o n t i n i t y b e i n g imposed t h r o u g h the use of m i l e s t o n e s . The model needed t o be extended t o a l l o w a F i g u r e 2.6 M o d e l l i n g Changes i n Number of Crews by V a r y i n g P r o d u c t i o n Rate change i n t h e number of crews at each s t a g e of the a c t i v i t y t o p r o v i d e an adequate breakdown of crew l e v e l l i n g . I f the number of crews i s i n c r e a s e d , the new crew can be s t a r t e d as soon as the o t h e r r e s o u r c e s ( m a t e r i a l s e t c . ) a r e made a v a i l a b l e . I f the 20 number of crews i s d e c r e a s e d , the f i r s t crew t o f i n i s h i t s c u r r e n t l e v e l i s dropped so as t o e x p e d i t e the crew l e v e l l i n g p r o c e s s . The F o u n d a t i o n study was a l s o found to c o n s i s t a n t l y i n v o k e n o n - r e g u l a r r e p e t i t i v e work p a t t e r n s . Furthermore, due to the r e l a t i v e l y s m a l l s i z e of the p r o j e c t , s i t e p e r s o n n e l o f t e n took advantage of c h a n g i n g the sequence of the work p a t t e r n s t o a l l e v i a t e problems such as s t o r a g e of m a t e r i a l , or d e l a y s on c e r t a i n f l o o r s . At one p o i n t , the sequence was t o t a l l y r e v e r s e d and the f i n i s h i n g a c t i v i t i e s were r e s c h e d u l e d from the top f l o o r downwards t o a l l o w f o r the l a t e shop drawings on the lower l e v e l s . These s t u d i e s c l e a r l y show a need f o r a more g e n e r a l d e f i n i t i o n . In p a r t i c u l a r , work p a t t e r n s c o n s i s t i n g of non-r e g u l a r r e p e t i t i o n must be r e c o g n i z e d . The a b i l i t y t o resequence the p a t t e r n must a l s o be examined. Recent s t e p s t o g e n e r a l i z e the r e p e t i t i v e s t r u c t u r e have been implemented i n response t o the needs of each study. These i n c l u d e the a b i l i t y t o model p a t t e r n s c o n s i s t i n g of s e m i - r e g u l a r r e p e t i t i o n ( i . e . work X l e v e l s , then s k i p Y) and a l s o a r e v e r s e o r d e r i n g of the s t r u c t u r e . These s t e p s respond t o the most common problems of the r e p e t i t i v e s t r u c t u r e and s e r v e to b r i d g e the gap u n t i l a g e n e r a l s t r u c t u r e can be implemented. 21 2.4.4.1 User I n t e r f a c e S i d e e f f e c t s of g e n e r a l i z i n g the s t r u c t u r e a r e i n c r e a s e d d a t a i n b o t h the i n p u t and s t o r a g e phase. At some p o i n t , the g e n e r a l i t y becomes s e l f d e f e a t i n g . T h i s t h e o r e t i c a l l y o c c u r s as the h i g h l e v e l i n f o r m a t i o n o b j e c t approaches e q u a l d a t a s t o r a g e and user time as i t s low l e v e l c o u n t e r p a r t s . However, i n r e a l i t y i t i s user time t h a t i s c o n s i d e r e d the g o v e r n i n g f a c t o r . R e g a r d l e s s of i t s m i n i m i z e d data s t o r a g e , a c o m p l i c a t e d user i n t e r f a c e w i l l cause the u s e r t o shun the program. A use r i n t e r f a c e must be d e s i g n e d t o m a i n t a i n a s i m p l e i n p u t p r o c e s s f o r the u s e r . T h i s s u g g e s t s t h a t i n p u t prompts be kept t o Laramee's s i m p l i f i e d d e f i n i t i o n u n l e s s the non-g e n e r a l i z e d v e r s i o n i s r e q u i r e d . Such methodology a l s o e n s u r e s minimum d a t a s t o r a g e , expanding the d a t a base f o r each a c t i v i t y as i t r e q u i r e s a g r e a t e r g e n e r a l i t y . C o n s t r u c t i o n p e r s o n n e l have shown a d e s i r e t o use the r e p e t i t i v e s t r u c t u r e . However, they f i n d i t d i f f i c u l t t o r e l a t e t o an i n p u t r o u t i n e based on l a b e l s . I t would c o n s i d e r a b l y ease t h e i r use of the system i f a s i m p l e g r a p h i c r e p r e s e n t a t i o n of the r e p e t i t i v e s t r u c t u r e c o u l d be implemented t o h e l p a f f i r m and r e a s s u r e the user of such i n p u t s . T h i s s t e p i s c u r r e n t l y b e i n g added; an example of i t s o u t p u t i s shown i n F i g u r e 2.7. 22 6 Z 5 2 A o •* 2 1 / / / / / B=1 C=6 D=1 E= 1 F = N / A 6=0 6 5 2 4 2 3 o J 2 1 B=1 C=6 w o r k 1 s k i p 1 D=1 E=1 F = N / A 6=1 D A Y S D A Y S < u Q \ I • crewl \ ere w2 cne wl \ crew2 \ B=6 C = l w o r k 2 s k i p 2 D=2 E=1 F=0 6=3 D A Y S D A Y S F i g u r e 2.7 Examples of G r a p h i c Output of the R e p e t i t i v e S t r u c t u r e 2.4.2 B) L o g i c R e l a t i o n s h i p s I t i s i m p o r t a n t t o r e v i e w the e f f e c t s t h a t r e o r d e r i n g has upon n o n - t y p i c a l l o g i c c o n s t r a i n t s which s t i l l e x i s t but may now p l a y a d i f f e r e n t r o l e . For example i n the case of F i g u r e 2.8, r e v e r s a l of sequence w i l l r e q u i r e the two n o n - t y p i c a l l o g i c l i n k s t o be broken and r e l i n k e d t o t h e o p p o s i t e end of the r e p e t i t i v e a c t i v i t y . A l l l i n k s a re made w i t h s p e c i f i c l o c a t i o n s 23 of t h e r e p e t i t i v e a c t i v i t y i n o r d e r t o r e t a i n the low l e v e l d a t a . C C F i g u r e 2.8 Reseqencinq and N o n - T y p i c a l L o g i c C o n s t r a i n t s Care must a l s o be taken w i t h t y p i c a l l o g i c l i n k s when a change i n sequence i s adopted f o r a group of r e p e t i t i v e a c t i v i t i e s . For example, F i g u r e 2.9 shows t h r e e r e p e t i t i v e a c t i v i t i e s which have been s c h e d u l e d . I f the "Form" a c t i v i t y was t o change i t s sequence, i t would.be a d v i s a b l e t o r e f l e c t t h a t change i n sequence i n the r e m a i n i n g two a c t i v i t i e s t o ensure an o p t i m i z a t i o n of c o n t i n u i t y between a c t i v i t i e s t o m i n i m i z e f l o a t t i m e . Grouping of r e p e t i t i v e a c t i v i t i e s o f t e n o c c u r on the s i t e . B i r e l l (Reference 3) r e f e r r e d t o them as shadow a c t i v i t i e s : each a c t i v i t y i s a c t i v a t e d as soon as i t s p r e d e c e s s o r i s completed (eg. c o n c r e t e i s poured as soon as the l a s t p i e c e of r e b a r i s i n 24 F i g u r e 2.9 Resequencing and T y p i c a l L o g i c C o n s t r a i n t s p l a c e ) . When c h a n g i n g the sequence of a group of a c t i v i t i e s the t y p i c a l l i n k s would a u t o m a t i c a l l y r e a d d r e s s t h e m s e l v e s . However, n o n - t y p i c a l l i n k s must be r e v i e w e d f o r p o s s i b l e r e d e f i n i t i o n of t h e i r r o l e s . T r a c k i n g of such l o g i c l i n k s c o u l d be g r e a t l y a i d e d by a g r a p h i c a l d i s p l a y of chosen a c t i v i t i e s and t h e i r l o g i c l i n k s . 2.4.2.1 System Loops Laramee's d e f i n i t i o n of the r e p e t i t i v e s t r u c t u r e l a c k e d the f a c i l i t y t o a s s i g n l o g i c l i n k s t o and from the same r e p e t i t i v e a c t i v i t y . When t h i s s i t u a t i o n o c c u r r e d ( F i g u r e 2.10) the a l g o r i t h m p e r c e i v e d i t as a " l o o p " i n the system. The l o o p i s caused by the a d o p t i o n of sequence s t e p o r d e r i n g from CPM .(Reference 12). A r e p e t i t i v e a c t i v i t y i s g i v e n a s i n g l e seqence s t e p so t h a t i t may be moved as a b l o c k of d a t a 25 ACTIVITY F i g u r e 2,10 A L o g i c Loop I n v o l v i n g a R e p e t i t i v e A c t i v i t y d u r i n g the Forward and Backward Pass. Thus, when a l o g i c check i s r u n , i t w i l l not accept a r e p e t i t i v e a c t i v i t y which has both a s u c c e s s o r and p r e d e c e s s o r from the same a c t i v i t y . In r e a l i t y , the r e p e t i t i v e a c t i v i t y spans many sequence s t e p s and can o f t e n h a n d le the above s i t u a t i o n when i t i s checked at i t s lower l e v e l . To c i r c u m v e n t t h i s problem, one c o u l d negate the l i n k which o c c u r e d a t the l a t e r moment i n time ( i . e . the r e t u r n l i n k t o a r e p e t i t i v e a c t i v i t y ) a l l o w i n g t h e Forward and Backward Passes t o pr o c e e d . The l i n k c o u l d then be r e i n s t a t e d as an independant l o g i c t e s t t o ensure lower l e v e l d a t a c o m p a t i b i l i t y . I f the s i n g l e a c t i v i t y was found t o be s c h e d u l e d w i t h i n the d u r a t i o n shown as C, no l o o p e x i s t s . However, i f the s i n g l e a c t i v i t y c o u l d not be s c h e d u l e d w i t h i n d u r a t i o n C (due t o a d u r a t i o n g r e a t e r than C or i n t e r f e r e n c e from l i n k s t o o t h e r a c t i v i t i e s ) a " c o n t i n u i t y " l o o p e x i s t s . 26 The s i t u a t i o n of a c o n t i n u i t y l o o p i n v o l v i n g a r e p e t i t i v e a c t i v i t y has been noted by Peer ( R e f e r e n c e 23) whose answer i s t o break the c o n t i n u i t y i n the r e p e t i t i v e p r o c e s s . However, t h i s s i t u a t i o n need not be a u t o m a t i c a l l y handled by the a l g o r i t h m . A c o n t i n u i t y l o o p i n the system can p o i n t out t o the user a m i s t a k e i n h i s l o g i c or a missed p o i n t of r e f e r e n c e . Given the s t r u c t u r e Of the l o o p , i t c o u l d then be p o s s i b l e t o r e d e f i n e the problem area by one of the many t o o l s a v a i l a b l e t o the s c h e d u l e r : such as s p l i t t i n g the s i n g l e a c t i v i t y , or r e d e f i n i n g i t s i n t e n t . I f no r e d e f i n i t i o n i s p o s s i b l e , the user can then make the d e c i s i o n t o a d j u s t c o n t i n u i t y f o r t h a t p a r t i c u l a r a c t i v i t y . To promote such s c h e d u l e m a n i p u l a t i o n i t would be e s s e n t i a l t o p r o v i d e the data i n a g r a p h i c a l format so t h a t t h e i r i n t e r a c t i o n c o u l d be e a s i l y seen. T h i s would once a g a i n suggest a g r a p h i c a l d i s p l a y of a c t i v i t i e s and t h e i r l o g i c l i n k s . 2.4.3 C) C o n t i n u i t y The purpose of r e p e t i t i v e a c t i v i t i e s i s t o promote c o n t i n u i t y of r e s o u r c e s by p r o v i d i n g a rhythm t o the p r o j e c t . T h i s c o n t i n u i t y can be seen as a doub l e h i e r a r c h y : a) p a r t i a l a c t i v i t y l e v e l b) t o t a l a c t i v i t y l e v e l 27 The p a r t i a l a c t i v i t y l e v e l i s d e r i v e d by e n s u r i n g c o n t i n u i t y of each r e s o u r c e on t h a t p a r t i c u l a r a c t i v i t y . T h i s was p r o v i d e d f o r i n Laramee's work by the l e v e l l i n g of shared r e s o u r c e s , m a t e r i a l h a n d l i n g , and crew a v a i l a b i l i t y ( S e c t i o n 2.2). The t o t a l a c t i v i t y l e v e l i s a c h i e v e d by the sum of the p a r t i a l a c t i v i t y l e v e l s . T h i s was p r o v i d e d f o r i n Laramee's work by the o v e r a l l p r o d u c t i o n r a t e , g i v e n the r e s o u r c e s a v a i l a b l e . Laramee's r e p e t i t i v e a c t i v i t y was b u i l t on the p a r t i a l a c t i v i t y l e v e l whereby the crew's rhythm was c o n s i d e r e d precedent ( i e . i f s p e c i f i e d 2 crews, each crew must work on every second d e s i g n a t e d l o c a t i o n ) . The t o t a l rhythm thus e v o l v e d , t a k i n g on the shape g e n e r a t e d by the p a r t i a l rhythms of the s t r u c t u r e . G i v e n a l a r g e v a r i a n c e i n the p r o d u c t i o n r a t e s of the l o c a t i o n s of the r e p e t i t i v e a c t i v i t y , the p r e c e d e n t of p a r t i a l rhythm o f t e n caused a s l o w i n g down of the t o t a l rhythm. T h i s was caused when the a l g o r i t h m demanded t h a t crew A p e r f o r m the next l o c a t i o n , r e g a r d l e s s t h a t crew B was i d l e ( F i g u r e 2.11). C o n s u l t a t i o n w i t h F o u n d a t i o n p e r s o n n e l q u i c k l y r e v e a l e d t h a t the c o n t i n u i t y of the t o t a l a c t i v i t y l e v e l was paramount t o the rhythm of the e n t i r e p r o j e c t . Crews were p e r c e i v e d as a f l e x i b l e r e s o u r c e , used t o a t t a i n the r e q u i r e d p r o d u c t i o n r a t e of the a c t i v i t y as a whole. T h i s suggested a major change t o Laramee's p h i l o s o p h y of the r e p e t i t i v e s t r u c t u r e . The r e p e t i t i v e a c t i v i t y needed t o be r e d e f i n e d t o a l l o w the t o t a l a c t i v i t y l e v e l t o t a k e precedence. U s i n g the crews as they became 28 < 7 1 * c r e w 1 6 L — / 'jcti I c r e w 2 5 0 7 Lliiil '" 1 l c r e w 1 4 Hi i i i ' " " 1 c r e w 2 • 3 l l " ' 1 c r e w l • 2 1 c r e w 2 1 l c r e w 1 D A Y S 8 1 2 B = 1 C = 7 D = 2 E = 4 . 4 . 4 2 . 2 . 2 , 2 F = 0 6 = 0 F i g u r e 2.11 C o n t i n u i t y of I n t e r n a l Rhythm a v a i l a b l e , time between l o c a t i o n s c o u l d be m i n i m i z e d hence a c c e l e r a t i n g the c u m u l a t i v e p r o d u c t i o n r a t e of the o v e r a l l s t r u c t u r e . T h i s would a l s o ensure an o p t i m a l d i s t r i b u t i o n of the crews f o r maximum u t i l i t y ( F i g u r e 2.12). C o n t i n u i t y a t the p a r t i a l a c t i v i t y l e v e l i s c o n t r o l l e d by a l a g f a c t o r f o r m a t e r i a l h a n d l i n g and a l a g f a c t o r f o r shared r e s o u r c e s . The i d e a i s t o model the time taken t o move a l l m a t e r i a l and a c q u i r e a l l shared r e s o u r c e s b e f o r e the a c t i v i t y can s t a r t . I t a l s o i m p l i e s t h a t one b a t c h of shared r e s o u r c e s i s s h a r e d by a l l crews. S i t u a t i o n s e x i s t where 2 or 3 batc h e s of s h a r e d r e s o u r c e s a r e a l l o t t e d between 4 t o 5 crews, or where each p a i r of crews has i t s own b a t c h of sh a r e d r e s o u r c e s . I t i s o f t e n found i n the c o n s t r u c t i o n of the h i g h - r i s e c o r e , or the to w e r s of a b r i d g e . These are s c h e d u l e d s p e c i f i c a l l y t o g i v e a c y c l e which i s u s u a l l y based on the a v a i l a b i l i t y of formwork and 29 F i g u r e 2.12 C o n t i n u i t y of E x t e r n a l Rhythm c o n c r e t e . Such s i t u a t i o n s impose a more c o m p l i c a t e d d e f i n i t i o n of s h a r e d r e s o u r c e s , y e t one t h a t i s used e x t e n s i v e l y i n l i n e a r p r o j e c t s . There i s a need t o a l l o w f o r the d e f i n i t i o n of m u l t i p l e batches of shared r e s o u r c e s , u s i n g the u s u a l premise of " f i r s t b a t c h a v a i l a b l e t o next w a i t i n g crew". There i s a t h i r d c h o i c e of c o n t i n u i t y of r e p e t i t i v e s t r u c t u r e s , t h a t of no c o n t i n u i t y . T h i s c h o i c e was o v e r l o o k e d by Laramee. The F o u n d a t i o n s t u d y , due t o i t s s m a l l s i z e , o f t e n f a i l e d t o p r o v i d e c o n t i n u i t y of c e r t a i n p e r c e i v e d r e p e t i t i v e a c t i v i t i e s . Once t h i s f a c t i s r e a l i z e d i t i s i m p o r t a n t t o be a b l e t o r e l a x c o n t i n u i t y f o r t h a t a c t i v i t y f o r i t r e s t r i c t s the t i m i n g of the l e v e l s t o be p e r f o r m e d . T h i s does not mean t h a t the model has f a i l e d . I t s i n i t i a l m o d e l l i n g as a r e p e t i t i v e s t r u c t u r e a l l o w e d much of the i n p u t d a t a t o be a u t o m a t i c a l l y c a l c u l a t e d . The l a t e r p e r c e p t i o n of no c o n t i n u i t y a l l o w e d the 30 l e v e l s of the s t r u c t u r e to a c t as i n d i v i d u a l a c t i v i t i e s ( i . e . the b l o c k of d a t a was broken down t o low l e v e l d a t a ) . An i m p o r t a n t e f f e c t of r e l a x i n g c o n t i n u i t y of a r e p e t i t i v e s t r u c t u r e i s i t s a b i l i t y t o model a shadow a c t i v i t y ( S e c t i o n 2.4.2). To ensure a shadow a c t i v i t y i s performed as soon as i t s p r e d e c e s s o r a l l o w s , i t cannot be r e s t r i c t e d t o the f i x e d shape of a r e p e t i t i v e a c t i v i t y ( u n l e s s both the p r e d e c e s s o r and i t s shadow a c t i v i t y can by p e r f e c t l y matched as r e p e t i t i v e a c t i v i t i e s and t h a t s i t e i m p l e m e n t a t i o n does not d e v i a t e from the model). However, a shadow a c t i v i t y cannot be executed u n l e s s i t s r e s o u r c e s a r e a v a i l a b l e ; a c o n s t r a i n t t h a t i s ensured by the i n t e r n a l l i n k s g e n e r a t e d f o r a r e p e t i t i v e a c t i v i t y . T h e r e f o r e , by m o d e l l i n g the shadow a c t i v i t y as a r e p e t i t i v e s t r u c t u r e and then r e l a x i n g the c o n t i n u i t y r e s t r a i n t , the l o g i c l i n k s imposed a l l o w the shadow a c t i v i t y t o bend t o t h e shape of i t s p r e d e c e s s o r , y e t l i m i t i t s f l e x i b i l i t y to the a v a i l a b i l i t y of i t s r e s o u r c e s . The case can occur where the shadow a c t i v i t y i s to b e g i n as soon as i t s p r e d e c e s s o r a l l o w s ; r e s o u r c e s a r e t o be a s s i g n e d t o such an a c t i v i t y upon r e q u e s t t o ensure i t s immediate p r o g r e s s i o n . T h i s s i t u a t i o n i s o f t e n seen when m o d e l l i n g " c u r i n g " times f o r newly poured s e c t i o n s of c o n c r e t e . Thus, t o a l l o w i t s a p p r o p r i a t e s c h e d u l i n g , the c o n t i n u i t y of a r e p e t i t i v e a c t i v i t y i s dropped a l o n g w i t h i t s i n t e r n a l l o g i c (page 10) t o ensure the i n s t a n t p r o v i s i o n of m a t e r i a l s and manpower. The e x t e r n a l l o g i c remains i n t a c t t o ensure the c o r r e c t placement of 31 the l o c a t i o n s of the shadow a c t i v i t y w i t h i t s p r e d e c e s s o r and p r e s e r v e i t s l i n k s t o the network. 2.4.4 D) C r i t i c a l i t y By imposing a f i x e d s t r u c t u r e f o r the r e p e t i t i v e a c t i v i t y , a new c o n s t r a i n t i s added t o s c h e d u l i n g t h e o r y . F l o a t i s now d e f i n e d by the a c t i v i t y ' s a b i l i t y t o be e x e c u t e d w i t h o u t c a u s i n g d e l a y i n the e a r l y s t a r t of downstream a c t i v i t i e s (Free F l o a t ) or p r o l o n g a t i o n of the p r o j e c t ( T o t a l F l o a t ) g i v e n t h a t c o n t i n u i t y of r e p e t i t i v e s t r u c t u r e s i s o b s e r v e d . In such a c a s e , a l l l o c a t i o n s ( i . e . low l e v e l a c t i v i t i e s ) w i t h i n the r e p e t i t i v e s t r u c t u r e ( i . e . h i g h l e v e l a c t i v i t y ) a r e p e r c e i v e d as h a v i n g i d e n t i c a l f l o a t . A s i m p l e example demonstrates t h i s ( F i g u r e 2.13). In t h i s c a s e , the Forward and Backward Pass c o n s i s t of moving t h r e e a c t i v i t i e s (two n o n - r e p e t i t i v e and one r e p e t i t i v e ) . S i n c e the r e p e t i t i v e a c t i v i t y i s moved as a b l o c k t o m a i n t a i n c o n t i n u i t y i t can be seen t h a t both passes g e n e r a t e i d e n t i c a l t ime-space m a t r i c e s and hence a l l a c t i v i t i e s a r e c r i t i c a l ( T o t a l F l o a t = 0 ) . A more d e t a i l e d l o o k at the s c h e d u l e w i l l show t h i s t o be t r u e _i_f c o n t i n u i t y i s observed. However, o n l y l o c a t i o n 1 and 2 of the r e p e t i t i v e a c t i v i t y must be performed i n time i n o r d e r t o f i n i s h the p r o j e c t a t time T. W h i l e c o n t i n u i t y of l e v e l s 3, 4, 5 and 6 i s d e s i r e d t o m a i n t a i n a rhythm on the j o b , i t cannot be s a i d t o be c r i t i c a l t o the p r o j e c t d u r a t i o n . O b v i o u s l y , t h e r e must be a d i s t i n c t i o n between c o n t i n u i t y r e g a r d e d as c r i t i c a l t o the p r o j e c t d u r a t i o n and c o n t i n u i t y f o r 32 F i g u r e 2.13 C o n t i n u i t y Imposing C r i t i c a l i t y the sake of r h y t h m i c p r o j e c t p r o g r e s s i o n . By a l l o w i n g the r e p e t i t i v e s t r u c t u r e t o be backpassed as low l e v e l d a t a ( i . e . l o c a t i o n by l o c a t i o n ) , the n o n - c r i t i c a l p o r t i o n s can be a l l o c a t e d t h e i r a p p r o p r i a t e f l o a t ( F i g u r e 2.14a). T h i s c o u l d then be used t o t h e u s e r ' s advantage. Having i d e n t i f i e d the n o n - c r i t i c a l l o c a t i o n s , i t i s p o s s i b l e t o reduce t h e i r p r o d u c t i o n r a t e , t h u s m a i n t a i n i n g c o n t i n u i t y and r e l e a s i n g a p o r t i o n of the r e s o u r c e s t o a s s i s t i n o t h e r a r e a s ( F i g u r e 2.14b). An a l t e r n a t i v e would be t o m a i n t a i n the same p r o d u c t i o n r a t e and invoke a d i s c o n t i n u i t y a l l o w i n g a l l r e s o u r c e s of the a c t i v i t y t o be a l l o c a t e d t o c r i t i c a l a r e a s and l a t e r r e t u r n e d t o the a c t i v i t y ( F i g u r e 2.14c). The u t i l i z a t i o n of the f l o a t can be l e f t t o the user t o a l l o c a t e as each s i t u a t i o n w a r r a n t s . A g r a p h i c d i s p l a y of the 33 2 4 6 8 D A Y S F i g u r e 2.14 C o n t i n u i t y and I t s Use of F l o a t 34 r e p e t i t i v e a c t i v i t y and i t s f l o a t would a i d g r e a t l y i n the m a n i p u l a t i o n of both c o n t i n u i t y and r e s o u r c e s . F i e l d s t u d y e n f o r c e s t h i s d e f i n i t i o n of c r i t i c a l i t y as c o n t i n u i t y i s not always c o n s i d e r e d e s s e n t i a l f o r a c t i v i t i e s o f f the c r i t i c a l p a t h . T h i s i s due t o p o s s i b l e r e s o u r c e r e a l l o c a t i o n of n o n - c r i t i c a l a c t i v i t i e s which c o u l d be u t i l i z e d t o s h o r t e n the p r o j e c t d u r a t i o n and thus by f a r overshadow the b e n e f i t s of c o n t i n u i t y of n o n - c r i t i c a l a r e a s . N o n - c r i t i c a l a r e a s were a l s o c o n s i d e r e d as a s t o c k p i l e of work t o be e x e c u t e d when the c r i t i c a l p a t h was found t o have an e x c e s s i v e r e s o u r c e p r o f i l e ( i . e . r a i n y days, m a t e r i a l s h o r t a g e , manpower c o n g e s t i o n , e t c . ) . 2.4.4.1 L o s s e s Due to L i n e a r R e p e t i t i o n I t can be seen t h a t i n v o k i n g c o n t i n u i t y i n t o a s c h e d u l e s h o u l d not be t aken l i g h t l y . W h i l e i t does a l l o w b e n e f i t s of rhythm and h i g h l e v e l i n p u t , i t can waste u s e f u l f l o a t i f p r o d u c t i o n r a t e s are not c a r e f u l l y chosen. The worst case model i s shown i n F i g u r e 2.15a. C o n t i n u i t y has d e l a y e d the " b l o c k " a c t i v i t y as the E a r l y S t a r t Date (ESD), g i v e n c o n t i n u i t y , i s 3 days l a t e r than the t r u e ESD. The 3 days of f l o a t cannot be u t i l i z e d by t h e s c h e d u l e r s i n c e the Free F l o a t and T o t a l F l o a t a r e c a l c u l a t e d from the ESD g i v e n c o n t i n u i t y . The best case model i s shown i n F i g u r e 2.15b. C o n t i n u i t y does not cause any i n c r e a s e i n p r o j e c t d u r a t i o n and i s t r u l y c r i t i c a l a t a l l l o c a t i o n s . In t r u e l i f e s i t u a t i o n s , the model w i l l f a l l between 35 5 z 4 a u o -> 2 2 4 6 8 10 D A Y S F i g u r e 2.15 Worst and B e s t Case Models of L i n e a r R e p e t i t i o n the b e s t and worst case l i m i t s . Where i t i s not p o s s i b l e t o m a n i p u l a t e the p r o d u c t i o n r a t e of the r e p e t i t i v e a c t i v i t y t o take advantage of such a f l o a t (due t o h i g h r e n t a l of equipment, l i m i t e d c r a n e time e t c . ) i t i s the d e l a y e d E a r l y S t a r t caused by c o n t i n u i t y t h a t must be c a r e f u l l y weighed a g a i n s t the g a i n s i n rhythm and h i g h l e v e l i n p u t . When t h i s t r a d e o f f of f l o a t v e r s u s r e p e t i t i o n was put f o r w a r d t o s i t e p e r s o n n e l , t h e y showed a s t r o n g l e a n i n g towards the case of r e p e t i t i o n , e s p e c i a l l y i f the a c t i v i t y i n v o l v e d a s u b c o n t r a c t o r f o r i t p r o v i d e s the G e n e r a l C o n t r a c t o r w i t h a 36 u s e f u l method of m i n i m i z i n g the problems caused by c o n g e s t i o n of workers on the s i t e by d e l a y i n g the s u b c o n t r a c t o r s s t a r t u n t i l h i s work p r o g r e s s i o n i s ensured. Once the s u b c o n t r a c t o r i s c a l l e d t o work, he can proceed a t a steady pace and thus a v o i d the problems of r e c a l l and m a t e r i a l s t o r a g e . T h i s i s an i m p o r t a n t c h a r a c t e r i s t i c of h i g h - r i s e c o n s t r u c t i o n as m a t e r i a l s t o r a g e space and work space i s o f t e n l i m i t e d . P e r s o n n e l however, d i d s t r e s s t h a t r e p e t i t i o n c o u l d be abandoned i f i t s f l o a t c h a r a c t e r i s t i c s were found t o have a s i g n i f i c a n t d e t r i m e n t a l e f f e c t on the c r i t i c a l p a t h . 37 2.5 The G e n e r a l R e p e t i t i v e S t r u c t u r e The aim of t h i s s e c t i o n i s t o p r o v i d e a g e n e r a l d e f i n i t i o n f o r the r e p e t i t i v e a c t i v i t y based on the r e c e n t s i t e s t u d i e s and the work done by Laramee and i t s f u r t h e r e x t e n s i o n s . T h i s d e f i n i t i o n t a k e s i n t o account the problems d i s c u s s e d i n the above s e c t i o n s and p r o v i d e s a model by which f u t u r e r e s e a r c h i n t h i s a r e a can be r e f e r r e d . F i r s t i t i s important t o p r e s e n t a d e f i n i t i o n of c e r t a i n terms p e r t i n e n t t o the r e p e t i t i v e s t r u c t u r e . R e p e t i t i o n : a p r o c e s s which i s r e p e a t e d a t two or more p o i n t s i n t i m e . C o n t i n u i t y : an u n i n t e r r u p t e d c o n n e c t i o n i n t i m e , space or development. R e p e t i t i v e A c t i v i t y : an a c t i v i t y or p r o c e s s t h a t i s r e c o g n i z e d by c o n s t r u c t i o n p e r s o n n e l t o d i s p l a y r e p e t i t i o n and enhance c o n t i n u i t y of r e s o u r c e s through r h y t h m i c p r o g r e s s i o n . Laramee's d e f i n i t i o n of the r e p e t i t i v e a c t i v i t y s t a t e d t h a t a l l l o c a t i o n s i n a g i v e n range s h o u l d be s e q u e n t i a l , thus r e q u i r i n g o n l y the f i r s t and l a s t l o c a t i o n s t o be s p e c i f i e d ( S e c t i o n 2.2). A comparison of the f i r s t and l a s t l o c a t i o n s a l s o p r o v i d e d the " d i r e c t i o n " the a c t i v i t y was t o f o l l o w . T h i s was not r e a l i z e d by Laramee but was i n i t i a t e d d u r i n g the l a t e r s i t e s t u d i e s ( S e c t i o n 2.4.1). 38 Laramee's d e f i n i t i o n was not found t o be f l e x i b l e enough t o model the m a j o r i t y of l o c a t i o n p a t t e r n s e v i d e n t i n r e p e t i t i v e a c t i v i t i e s . The e x t e n s i o n s of " s k i p p i n g " c e r t a i n l o c a t i o n s on a r e g u l a r p a t t e r n and r e v e r s e o r d e r i n g of the s t r u c t u r e were added to the d e f i n i t i o n ( S e c t i o n 2.4.1). The r e s o u r c e p r o f i l e of Laramee 1s d e f i n i t i o n was found t o be i n a d e q u a t e . A s t a g i n g e f f e c t was added t o d i v i d e the a c t i v i t y i n t o segments, where each segment c o u l d have i t s own p r o d u c t i o n r a t e ( S e c t i o n 2.3). The a u t h o r recommends t h a t the f o l l o w i n g a t t r i b u t e s be added t o the extended Laramee's model t o a c h i e v e a g e n e r a l model f o r the r e p e t i t i v e s t r u c t u r e . L o c a t i o n p a t t e r n s m o d e l l e d by the r e p e t i t i v e a c t i v i t y must i n c l u d e n o n - r e g u l a r c a s e s ( S e c t i o n 2.4.1) as t h e p h y s i c a l o u t l a y of a p r o j e c t does not always l e n d i t s e l f t o a r e g u l a r p a t t e r n . The r e s o u r c e p r o f i l e must be extended t o a l l o w a crew p r o f i l e t o be d etermined f o r each stage of the a c t i v i t y ( S e c t i o n 2.4.1).. M u l t i p l e b a t c h e s of shared r e s o u r c e s must be a l l o w e d as they p l a y an i m p o r t a n t r o l e i n the rhythm of r e p e t i t i v e t a s k s ( S e c t i o n 2.4.3). I t i s f u r t h e r recommended t h a t a v i s u a l d i s p l a y of the r e p e t i t i v e a c t i v i t y be a c c e s s i b l e so t h a t the a f f e c t of a l l a t t r i b u t e s on the a c t i v i t y ' s shape can be q u i c k l y demonstrated to the u s e r i n a comprehensive manner and t h a t a p p l i c a b l e a d j u s t m e n t s may be made. 39 The s i t e s t u d i e s show t h a t the r e p e t i t i v e s t r u c t u r e s h o u l d be based on a d i s t i n c t s e t of v a r i a b l e s t h a t have s t r o n g r o o t s i n the c o n s t r u c t i o n i n d u s t r y . The a t t r i b u t e s r e q u i r e d of a r e p e t i t i v e a c t i v i t y a re summarized below and expanded upon i n the f o l l o w i n g s e c t i o n s . A) P r o v i d e a d a t a s t r u c t u r e t h a t : 1) u t i l i z e s h i g h l e v e l i n f o r m a t i o n o b j e c t s t o m i n i m i z e use r i n p u t and d a t a s t o r a g e . 2) a l l o w s m a n i p u l a t i o n of work p a t t e r n s as l a r g e b l o c k s of d a t a . B) P r o v i d e f l e x i b i l i t y t h a t : 1) e n a b l e s m o d e l l i n g of the m a j o r i t y of work p a t t e r n s found i n c o n s t r u c t i o n . 2) a l l o w s changes i n the a c t i v i t y ' s shape t o adapt t o the c h a n g i n g c o n s t r u c t i o n s i t e . C) P r o v i d e c o n t i n u i t y : 1) a t the p a r t i a l a c t i v i t y l e v e l t o promote c o n t i n u i t y of r e s o u r c e s . 2) a t the t o t a l a c t i v i t y l e v e l , t o o b t a i n the b e n e f i t s of rhythm. 40 2.5.1. A) Data S t r u c t u r e W h i l e the i n p u t s r e q u i r e d t o g e n e r a t e the s e q u e n t i a l f i l e do not c o n s t i t u t e the major a r e a s of s a v i n g i n d a t a i n p u t and s t o r a g e (Reference 16), they a r e the major i n p u t s v i s i b l e t o the u s e r . As such, they form the essence of the user i n t e r f a c e and must promote s i m p l i c i t y of use w h i l e a l l o w i n g a g e n e r a l d e f i n i t i o n of the r e p e t i t i v e a c t i v i t y . The i n p u t s r e q u i r e d by the u s e r t o promote the g e n e r a l model f o r the r e p e t i t i v e s t r u c t u r e a r e : a) a c t i v i t y name, code number, o t h e r g e n e r a l f a c t o r s b) sequence (eg. 1 t o 6 e x c l u d e 3) c) s t a g e s (eg. 1-4, 5-6) d) p r o d u c t i o n r a t e s per stage (eg. 4,2) e) number of crews per st a g e ( e g . 2,2) f ) number of batc h e s of s h a r e d r e s o u r c e s (eg. B=1) g) time r e q u i r e d f o r shared r e s o u r c e s (eg. SS=2) h) time r e q u i r e d f o r m a t e r i a l h a n d l i n g (eg. FS=0) The l o c a t i o n s a re e n t e r e d by a s i m p l e s e t of commands d e s i g n e d t o m i n i m i z e user i n p u t and d a t a s t o r a g e . A t.o B, e x c l u d e C,D,E,F.... p l u s S t o T, e x c l u d e U,V,W,X 41 T h i s i s f o l l o w e d by the st a g e s which e s s e n t i a l l y d i v i d e s the r e p e t i t i v e a c t i v i t y i n t o segments. A p r o d u c t i o n r a t e and crew p r o f i l e a r e then added f o r each s t a g e and i s assumed t o be the same f o r a l l s e q u e n t i a l l o c a t i o n s of t h a t s t a g e . The number of bat c h e s of sh a r e d r e s o u r c e s i s g i v e n and i s assumed to be c o n s t a n t f o r the d u r a t i o n of the a c t i v i t y . The time t h a t a crew r e q u i r e s the shared r e s o u r c e s i s denoted, a l o n g w i t h the time r e q u i r e d f o r the crew t o move o t h e r r e s o u r c e s between i t s l o c a t i o n s . Examples of r e p e t i t i v e a c t i v i t i e s g e n e r a t e d from the s e i n p u t s a r e shown i n F i g u r e 2.16. The d a t a base used w i l l depend on the computing environment i n which the a l g o r i t h m i s housed, i t s p r i m a r y f u n c t i o n s and i t s i n t e g r a t i o n t o o t h e r a r e a s of p r o j e c t management. However, a l l d a t a bases must be a b l e t o produce a d e f i n i t i o n of t h e r e p e t i t i v e a c t i v i t y w i t h low l e v e l d a t a . T h i s p r o v i d e s a r e f e r e n c e p o i n t from which a l l bases can be compared. The au t h o r assumes the i n p u t can produce a s e q u e n t i a l f i l e ( F i g u r e 2.17) c o n s i s t i n g of the l o c a t i o n s , a l i s t of s t a g e s , the number of crews w o r k i n g and t h e i r p r o d u c t i o n r a t e f o r each s t a g e . T h i s i s l i n k e d t o the memory c o n t a i n i n g the number of ba t c h e s of shared r e s o u r c e s used and the time r e q u i r e m e n t s f o r shared r e s o u r c e s and m a t e r i a l h a n d l i n g . The above d e f i n i t i o n e n a b l e s most work p a t t e r n s t o be mo d e l l e d u s i n g v e r y l i t t l e user i n p u t . I t i s not c o n s i d e r e d w o r t h w i l e g e n e r a l i z i n g the d e f i n i t i o n f u r t h e r and i n c r e a s i n g c o m p l e x i t y of user i n p u t . Y e t , i t i s not a d v i s a b l e t o d e t e r a 42 SEQUENCE ( 1 - 7 ) S T A G E S ( 1 - 3 . 4 - 7 ) PROD. R A T E S / S T A G E ( 4 . 2 ) • C R E V S / S T A G E ( 2 . 2 ) B A T C H E S OF SHARED RESOURCES TIME FOR SHARED RESOURCES TIME FOR M A T E R I A L HANDLING (B=1) (SS=0) (FS=0) 7 6 5 A 3 2 1 C B A B A 8 D A Y S 10 12 1 4 16 SEQUENCE S T A G E S PROD. R A T E S / S T A G E • C R E V S / S T A G E ( 2 . 3 ) B A T C H E S OF SHARED RESOURCES TIME FOR SHARED RESOURCES TIME FOR M A T E R I A L HANDLING ( 1 - 7 exc lude 3 . 4 ) ( 1 - 4 . 5 - 7 ] ( 3 . 4 ) (B=2I (SS=2) (FS=1) SEQUENCE S T A G E S PROD. R A T E S / S T A G E • C R E V S / S T A G E ( 3 - 6 . 1 - 2 , 7 ) ( 1 - 7 ) ( 3 ) ( 2 ) B A T C H E S OF SHARED RESOURCES IB=1) TIME FOR SHARED RESOURCES (SS=0) TIME FOR M A T E R I A L HANDLING (FS=0) SEQUENCE ( 1 - 4 . 7 - 5 ) S T A G E S ( 1 - 7 ) PROD. R A T E S / S T A G E ( 3 ) • C R E V S / S T A G E ( 2 ) B A T C H E S OF SHARED RESOURCES TIME FOR SHARED RESOURCES TIME FOR M A T E R I A L HANDLING IB=1J (SS=0) (FS=1) F i g u r e 2.16 Examples Based on the G e n e r a l D e f i n i t i o n R e p e t i t i v e A c t i v i t y 43 L O C A T I O N P R O D U C T I O N R A T E * OF C R E W S 1 4 2 2 4 2 2 5 6 } Denotes B S S F S 1 2 0 F i g u r e 2.17 The S e q u e n t i a l F i l e INPUT us e r e n t e r i n g a work p a t t e r n i f i t i s c o n s i d e r e d f a v o u r a b l e t o be m o d e l l e d . The model d e s c r i b e d a l l o w s the d a t a t o be e n t e r e d on a l o c a t i o n by l o c a t i o n b a s i s i f d e s i r e d . W h i l e t h i s e l i m i n a t e s some s a v i n g i n s t o r a g e of t h i s p a r t i c u l a r r e p e t i t i v e a c t i v i t y , advantage can s t i l l be taken i n the g a i n s i n c o n t i n u i t y , m a n i p u l a t i o n of l a r g e b l o c k s of d a t a , and the m o d e l l i n g of shadow a c t i v i t i e s . The graph shown i n F i g u r e 2.18a i l l u s t r a t e s the t r a d e o f f between g e n e r a l i t y of the r e p e t i t i v e d e f i n i t i o n and i t s c o r r e s p o n d i n g i n p u t . The d a t a has been d e v e l o p e d based on the number of c h a r a c t e r s t h a t must be i n p u t by the u s e r t o model each l e v e l of g e n e r a l i t y of the r e p e t i t i v e model. T h i s measurement was used as i t i s an a b s o l u t e v a l u e and i s not 44 e f f e c t e d by the data base s t r u c t u r e i n which i t i s housed. The s t a g e s have been set a t f i v e l o c a t i o n s each. The r e g u l a r r e p e t i t i v e a c t i v i t y denotes a l l s e q u e n t i a l l o c a t i o n s a r e i n c l u d e d , as per Laramee's model. The n o n - r e g u l a r r e p e t i t i v e a c t i v i t y i s based on 20% of l o c a t i o n s e x c l u d e d . The m i n i m a l r e p e t i t i v e a c t i v i t y i s based on 60% of l o c a t i o n s e x c l u d e d . The low l e v e l a c t i v i t y i s shown f o r comparison and i s based on the CPM minimum of one p r e d e c e s s o r and one s u c c e s s o r per l o c a t i o n . The c h a r a c t e r s c o u n t e d c o r r e s p o n d o n l y t o those i n p u t r e q u i r e m e n t s shown above which must be e n t e r e d by the user and cannot be p r e d e f i n e d by the user i n t e r f a c e . Note, t h i s does not i n c l u d e the a c t i v i t y d e s c r i p t i o n which i s o n l y e n t e r e d once f o r the r e p e t i t i v e a c t i v i t y y e t must be e n t e r e d a t every l o c a t i o n w i t h low l e v e l d a t a . The c h a r a c t e r s counted a l s o do not i n c l u d e any l i n k s made between the r e p e t i t i v e a c t i v i t y (or the low l e v e l d a t a used f o r comparison) and any o t h e r . p a r t s of the network. The graph shown i n F i g u r e 2.18b h i g h l i g h t s the i n c r e a s i n g e f f i c i e n c y of the r e g u l a r , n o n - r e g u l a r and m i n i m a l r e p e t i t i v e p a t t e r n s w i t h the i n c r e a s i n g s i z e of the a c t i v i t y , s e t t l i n g down t o .9, 1.1 and 1.5 c h a r a c t e r s per l o c a t i o n r e s p e c t i v e l y . The low l e v e l d a t a r e q u i r e s a c o n s i s t a n t 4.0 c h a r a c t e r s per l o c a t i o n t o model a r e p e t i t i v e a c t i v i t y and does not have the advantage of imposing c o n t i n u i t y t h r o u g h the m a n i p u l a t i o n of l a r g e b l o c k s of d a t a . 45 >• O \-Q. CO at LU u < < u M A R G I N A L R E P E T I T I O N N O N - R E G U L A R R E P E T I T I O N R E G U L A R R E P E T I T I O N 10 1 5 2 0 2 5 3 0 3 5 4 0 in at LU H U < < X u H 3 3 2 0£ LU a. L O C A T I O N ( A ) L O W L E V E L D A T A M A R G I N A L N O N - R E G U L A R R E G U L A R 1 0 1 5 2 0 2 5 3 0 3 5 4 0 L O C A T I O N ( B ) F i g u r e 2.18 T r a d e o f f Between G e n e r a l i t y of R e p e t i t i v e A c t i v i t y  D e f i n i t i o n and E f f i c i e n c y of Data Input 46 2.5.2. B) F l e x i b i l i t y Changes i n s e q u e n t i a l o r d e r of the l o c a t i o n s a r e a l l o w e d by r e e n t e r i n g the p a t t e r n of the a c t i v i t y over the o l d d a t a . The s t a g e s and o t h e r d a t a w i l l remain t i e d t o each l o c a t i o n and thus m a i n t a i n d a t a i n t e g r i t y w i t h the r e o r d e r i n g p r o c e s s . However, t h i s d a t a can a l s o be r e e n t e r e d i f r e q u i r e d . Changes due t o u p d a t i n g w i l l be d i s c u s s e d i n Chapter I I I . 2.5.3 C) C o n t i n u i t y C o n t i n u i t y a t the p a r t i a l l e v e l must p r o v i d e a smooth fl o w of each r e s o u r c e a l o n g i t s l o c a t i o n s as i t p r o g e s s e s . T h i s can be d e f i n e d as t h r e e c o n s t r a i n t s : a) m a t e r i a l h a n d l i n g between f l o o r s of a p a r t i c u l a r c rew b) s h a r i n g of r e s o u r c e s between m u l t i p l e crews c) a l l o c a t i o n of crews t o p a r t i c u l a r l e v e l s The f i r s t two c o n s t r a i n t s can be d e a l t w i t h by u s i n g the FS and SS l i n k s as d e f i n e d by Laramee ( S e c t i o n 2.2 ). The t h i r d c o n s t r a i n t must be ha n d l e d by e n s u r i n g t h a t each crew i s r e a l l o c a t e d as soon as i t completes a l o c a t i o n . By c o n t r o l l i n g a l l t h r e e c o n s t r a i n t s , c o n t i n u i t y a t the t o t a l a c t i v i t y l e v e l e nsures t h a t the a c t i v i t y as a whole 47 p r o g r e s s e s i n the most e x p e d i e n t manner p o s s i b l e by s t a r t i n g each s u c c e e d i n g l o c a t i o n as soon as a l l r e s o u r c e s a r e a v a i l a b l e , t h u s m i n i m i z i n g any p e r i o d of n o n - p r o d u c t i v i t y . 48 2.6 The R e p e t i t i v e B u i l d i n g P r o c e s s The s i t e s t u d i e s have shown t h a t b u i l d i n g a r e p e t i t i v e a c t i v i t y r e q u i r e s a knowledge of a v a i l a b l e r e s o u r c e s (crews, m a t e r i a l , shared r e s o u r c e s ) and t h e i r placement i n time and space. Each l o c a t i o n t o be p r o c e s s e d must know: 1) Which crew w i l l be a v a i l a b l e f i r s t , 2) how l o n g i t w i l l t a k e the crew t o t r a n s p o r t t h e i r m a t e r i a l s and 3) when w i l l s hared r e s o u r c e s be a v a i l a b l e from o t h e r crews. A l t h o u g h each l o c a t i o n must s a t i s f y the t h r e e c r i t e r i a l i s t e d above, the problem can be s i m p l i f i e d t o "keeping the crews p r o d u c t i v e " . Shared r e s o u r c e s and time f o r m a t e r i a l h a n d l i n g a r e r e s o u r c e s which d i c t a t e i f a crew i s a b l e t o work. Thus, g i v e n an a v a i l a b l e crew, i t i s p o s s i b l e t o f i n d when i t may s t a r t i t s next l o c a t i o n by the amount of time i t t a k e s t o a c q u i r e a b a t c h of s h a r e d r e s o u r c e s from a n o t h e r crew, and move i t s o t h e r m a t e r i a l s from the l a s t l o c a t i o n completed t o the next l o c a t i o n t o be p erformed. The d e f i n i t i o n of the p r o c e s s i s analagous t o a s i m u l a t i o n model ( R e f e r e n c e 14). The o n l y p o i n t s i n time t h a t must be examined a r e when a crew completes a l o c a t i o n . I t i s then a s s i g n e d t o i t s next l o c a t i o n a q u i c k l y as p o s s i b l e . Thus th e p r o c e s s can be m o d e l l e d as s i m u l a t i o n u s i n g n e x t - e v e n t 49 i n c r e m e n t i n g based on the crew's f i n i s h date f o r each l o c a t i o n . The s i m u l a t i o n p r o c e s s c a l l s f o r m u l t i p l e crews and m u l t i p l e batches of shared r e s o r c e s . P o o l s must be s e t up t o keep t r a c k of these v a r i a b l e s . P o o l A ( F i g u r e 2.19) denotes a t a b l e c o n t a i n i n g each crew, the day i t i s a v a i l a b l e ( S a ) , and weather i t i s c u r r e n t l y employed by the r e p e t i t i v e a c t i v i t y . P o o l B ( F i g u r e 2.19) denotes a t a b l e c o n t a i n i n g each crew, the day t h a t shared r e s o u r c e s w i l l be a v a i l a b l e ( S b ) , and the crews which are c u r r e n t l y u s i n g the shared r e s o u r c e s . 2.6.1 The F l o w c h a r t . The s e q u e n t i a l f i l e INPUT ( F i g u r e 2.17) i s used t o read the a c t i v i t y d ata f o r the s i m u l a t i o n p r o c e s s d i s c u s s e d i n the f o l l o w i n g s e c t i o n . The s e q u e n t i a l f i l e OUTPUT ( F i g u r e 2.20) houses the f i n i s h e d r e p e t i t i v e a c t i v i t y ; i t c o n t a i n s each l o c a t i o n p r o c e s s e d , the crew number and i t s p r o d u c t i o n r a t e , i t s E a r l y S t a r t and E a r l y F i n i s h Date g i v e n c o n t i n u i t y , and a p r e d e c e s s o r l i s t of SS l i n k s . A column i s not r e q u i r e d f o r the FS l i n k s as they e x i s t between a l l l o c a t i o n s of each crew and can t h e r e f o r e be d e r i v e d from the crew number column..However, SS l i n k s j o i n l o c a t i o n s t h a t use the same b a t c h of shared r e s o u r c e s and a r e not c o n f i n e d t o s p e c i f i c crews. The f l o w c h a r t f o r the b u i l d i n g of the r e p e t i t i v e a c t i v i t y i s shown i n F i g u r e 2.21. The a l g o r i t h m s t a r t s a t Day 1 ( S i = 1) 50 C R E W * Sa C R E W S WORKING 1 • 2 * 3 4 5 POOL A C R E W * Sb S H A R E D RESOURCES 1 * 2 3 4 5 POOL B F i g u r e 2.19 The Use of P o o l s i n the S i m u l a t i o n P r o c e s s and f i l l s i n P o o l s A and B ( a l l Sa and Sb = 1) t o show a l l crews a r e c u r r e n t l y a v a i l a b l e . The X b a t c h e s of s h a r e d r e s o u r c e s a re g i v e n t o the f i r s t X crews by a f f i x i n g a f l a g (denoted by an a s t e r i s k ) t o show t h e i r c u r r e n t l o c a t i o n ( i . e . i n case of a t i e , g i v e t o the l o w e s t crew number). These d e f a u l t s w i l l be changed i n the case of .update d a t a t o r e f l e c t the c u r r e n t s t a t u s of the a c t i v i t y . The update phase w i l l be d i s c u s s e d i n Chapter I I I . The INPUT f i l e i s used t o det e r m i n e the next l o c a t i o n t o be m o d e l l e d , the number of crews w o r k i n g a t t h i s stage and t h e i r p r o d u c t i o n r a t e . The l o c a t i o n and p r o d u c t i o n r a t e a re p l a c e d i n 51 LOCATION C R E W * PRODUCTION RATE S F S S 1 1 4 1 4 2 2 4 3 6 1 4 1 4 5 8 2 5 2 2 7 8 4 6 1 2 9 1 0 5 F i g u r e 2.20 The S e q u e n t i a l F i l e OUTPUT f i l e OUTPUT t o denote the c o r r e c t m o d e l l i n g o r d e r . P o o l A i s checked t o ensure the c o r r e c t number of crews i s wo r k i n g i n t h i s s t a g e , each b e i n g denoted by an a s t e r i s k . In the case of add i n g a crew, the l o w e s t crew number not wo r k i n g i s i n i t i a t e d . In the case of l o s i n g a crew, the f i r s t crew t o f i n i s h i t s c u r r e n t l o c a t i o n i s dropped. The next a v a i l a b l e crew i s found by s e a r c h i n g P o o l A f o r the e a r l i e s t Sa which d i s p l a y s an a s t e r i s k . T h i s i s based on the crew's f i n i s h date of the l a s t l o c a t i o n m o d e l l e d p l u s time r e q u i r e d t o move m a t e r i a l s t o the new l o c a t i o n (Sa=Fi+FS+1). Note, one u n i t of time i s added due t o the d e f i n i t i o n of the s t a r t and f i n i s h d a t e s (see Laramee, R e f e r e n c e 16). The crew's number i s then p l a c e d i n f i l e OUTPUT. The f i r s t a v a i l a b l e b a t c h of s h a r e d r e s o u r c e s i s found by s e a r c h i n g P o o l B f o r the e a r l i e s t Sb which d i s p l a y s an a s t e r i s k . T h i s i s based on the crew's s t a r t date of the l a s t l o c a t i o n m o d e l l e d p l u s time 52 i = 0 S i = 1 Z3Z A l l S a and S b = 1 * to f i r s t N c r ews in Pool B Update Data i = i • 1 I ( i >Locat ions?  | NO From Tile INPUT get - next l o ca t i on - * c r e w s work ing - product ion rate I Add or de lete * in Pool A to show current c r ews work ing  T Get f i r s t ava i l ab le c r ew by p i ck ing ea r l i e s t s t a r t ( S a ) f r om Pool A . I Get f i r s t ava i l ab le batch of shared resources by p i ck ing ea r l i e s t s t a r t ( 5 b ) f r om Pool B. T r an s f e r * to current c r ew us ing them Take l a tes t of S a and S b to show ea r l i e s t s t a r t g iven e l l c ons t r a i n t s . S i = g r e a t e s t o f ( S a . S b ) A Ca l cu l a te f i n i s h date of l o ca t i on by adding I ts rema in ing durat ion. F i = S i • R E M D U R Ca l cu l a t e when c rew i s ava i l ab l e next. S a = F i • F S * 1 Ca l cu l a te when the batch of shared resources w i l l be ava i l ab le next. S b = S i • S S END PLACE LOCATION ""'"""III" AND PRODUCTION RATE tM FILE OUTPUT Hiitiiiiitiljiii* PLACE CPEW * 1 INFILEOUTPUT nmmiijjlli' PLACES! 10FILEOUTPUT . PLACE Fi I"" i>NFILEOUTPUT PLACES* IM FILE OUTPUT III"-PLACE Sd 10 FILE OUTPUT F i g u r e 2.21 F l o w c h a r t of the R e p e t i t i v e A c t i v i t y B u i l d i n g P r o c e s s 53 r e q u i r e d t o use shared r e s o u r c e s (Sb=Si+SS). The a s t e r i s k i s then removed from t h i s crew and p l a c e d w i t h the crew at the c u r r e n t l o c a t i o n . The l o c a t i o n from which the b a t c h of shared r e s o u r c e s was p r o c u r e d i s a l s o p l a c e d i n t h e p r e d e c e s s o r column of the f i l e OUTPUT t o denote the SS l i n k between the l o c a t i o n s . The l a t e r of Sa and Sb denotes the time a t which the c u r r e n t l e v e l may be mo d e l l e d u s i n g the f i r s t a v a i l a b l e crew, g i v e n t h a t the m a t e r i a l s a r e a l r e a d y t h e r e t o be used and t h a t shared r e s o u r c e s a re a v a i l a b l e from the l a s t crew who used them. T h i s s t a r t ( S i ) i s then p l a c e d i n f i l e OUTPUT. The f i n i s h d a t e of the l e v e l i s found by a d d i n g i t s p r o d u c t i o n r a t e t o i t s s t a r t ( F i = S i + P i ) and i s a l s o p l a c e d i n f i l e OUTPUT. P o o l A i s then updated t o show when the c u r r e n t crew w i l l be a v a i l a b l e n e x t . P o o l B i s updated t o show when the c u r r e n t l e v e l w i l l be f i n i s h e d w i t h the shared r e s o u r c e s . T h i s p r o c e s s i s r e p e a t e d f o r each f l o o r of the r e p e t i t i v e a c t i v i t y t o be m o d e l l e d . The f i n i s h e d model i s c o n t a i n e d i n f i l e OUTPUT and i s ready t o be s c h e d u l e d . An example of the f i n i s h e d model i s shown below i n F i g u r e 2.22 a l o n g w i t h i t s INPUT and OUTPUT f i l e s . Each crew d i s p l a y s an FS l i n k between i t s l o c a t i o n s t o ens u r e time f o r m a t e r i a l h a n d l i n g . SS l i n k s a r e d i s p l a y e d between the a p p r o p r i a t e crews to ensure the a v a i l a b i l i t y of shared r e s o u r c e s . Note the g e n e r a l s t u c t u r e of the a c t i v i t y can be e a s i l y checked by comparing the INPUT f i l e w i t h the v i s u a l d i s p l a y p r o v i d i n g feedback i n a form 54 t h a t can be e a s i l y absorbed; l o c a t i o n s m o d e l l e d , s t a g e s and p r o d u c t i o n r a t e s a r e s e l f e v i d e n t . C l o s e r s c r u t i n y , such as t r a c k i n g of crews and batches of s h a r e d r e s o u r c e s i s p o s s i b l e by v i e w i n g the OUTPUT f i l e . 2.7 Summary The r e p e t i t i v e a c t i v i t y has been d e v e l o p e d based on the needs of the c o n s t r u c t i o n i n d u s t r y . The a l g o r i t h m d e s c r i b e s a model by which the user may u t i l i z e t he p r o c e s s of r e p e t i t i o n and rhythm on the c o n s t r u c t i o n s i t e . Use of c o n s t r u c t i o n t e r m i n o l o g y and g r a p h i c feedback promotes i t s a c c e p t a n c e as a u s e f u l management t o o l . The f o r e g o i n g model i s not y e t i n t e g r a t e d i n t o the system a t t h e U n i v e r s i t y of B r i t i s h C o l umbia. However, f i e l d s t u d i e s have shown the need f o r the management support i t p r o v i d e s . LOCATION PRODUCTION RATE * OF C R E W S 1 4 2 2 4 2 2 5 6 I Denotes ' / stage B S S F S 1 2 0 I N P U T F I L E LOCATION CREW * PRODUCTION RATE S F SS 1 1 4 1 4 2 2 4 3 6 1 4 1 4 5 8 2 5 2 2 7 8 4 6 1 2 9 1 0 5 O U T P U T F I L E F i g u r e 2.22 The F i n i s h e d Model of the R e p e t i t i v e A c t i v i t y 56 CHAPTER I I I CONTINUOUS UPDATING 3. 1 I n t r o d u c t i o n The purpose of t h i s c h a p t e r i s t o focus on the problems of u p d a t i n g a c o m p u t e r i z e d s c h e d u l e t o e f f e c t i v e l y m o n i t o r the p r o j e c t . The methods by which the c o n s t r u c t i o n i n d u s t r y m o n i t o r s the c o n s t r u c t i o n p r o c e s s a r e examined and r e l a t e d i n t o a c o m p u t e r i z e d s c h e d u l e a l g o r i t h m c a p a b l e of h a n d l i n g day t o day changes on s i t e . A computer s c h e d u l i n g a l g o r i t h m which can produce a c l e a r and p r e c i s e l o g i c network from a s i m p l e s e t of commands would be exp e c t e d t o t h r i v e i n the c o n s t r u c t i o n i n d u s t r y . Yet i t has not happened. Users have thrown away t h e i r s c h e d u l e i n f r u s t r a t i o n e a r l y i n the p r o j e c t . Computer s c h e d u l i n g has been t o u t e d as a u s e f u l means of g e t t i n g t o know the c h a r a c t e r i s t i c s of the j o b , but not u s e f u l f o r c o n t r o l ( D a v i s , R e f e r e n c e 7 ) . Lack .of c o n t r o l has been a t t r i b u t e d t o l a c k of model f l e x i b i l i t y . C o n t r o l can o n l y be implemented when the s c h e d u l e r e f l e c t s the day t o day s t a t u s of the p r o j e c t so t h a t changes and t h e i r e f f e c t s can be e v a l u a t e d . The u n r e s p o n s i v e n a t u r e of e x i s t i n g models has f o r c e d u s e r s t o reduce u p d a t i n g p e r i o d s t o u n a c c e p t a b l e l i m i t s ; once per month i s t y p i c a l . T h i s p r e c l u d e s 57 any e f f i c i e n t c o n t r o l of the p r o j e c t s i n c e i t r e f l e c t s a net e f f e c t o f a l l the changes thus o b s c u r i n g d e t e c t i o n of r e s p o n s i b i l i t y t o c o s t and performance ( F o n d a h l , R e f e r e n c e 11). W h i l e t h e r e i s a l a c k of l i t e r a t u r e on u p d a t i n g , Fondahl and D a v i s r e f l e c t the mood of the c o n s t r u c t i o n i n d u s t r y towards the u s e a b i l i t y of m o n i t o r i n g p r o j e c t s w i t h a c o m p u t e r i z e d s c h e d u l i n g a l g o r i t h m . E x i s t i n g models a r e u n w i e l d y i n t h e i r a b i l i l t y t o change w i t h the ever moving c o n s t r u c t i o n s i t e . Thus, they f a i l t o supply the user w i t h up-to-date s c h e d u l e changes and cannot r e f l e c t t o a C o n s t r u c t i o n Management I n f o r m a t i o n System (CMIS) schedule e f f e c t s on o t h e r a s p e c t s of the p r o j e c t . T h i s c h a p t e r d e f i n e s an u p d a t i n g procedure which can respond t o the u s e r s needs and maximize the p o t e n t i a l of a CMIS. I t a l s o proposes an a l g o r i t h m which p r o v i d e s a c o n t i n u o u s u p d a t i n g f a c i l i t y based on t y p i c a l s c h e d u l e p r o g r e s s d a t a . The r e s u l t i s a s c h e d u l i n g package which i s a b l e t o p r o v i d e the user w i t h an ongoing p i c t u r e of the s c h e d u l e t o h e l p i n the everyday d e c i s i o n a n a l y s i s and c o n t r o l of the p r o j e c t . 3.2 C r i t e r i a Used t o Promote the Use of U p d a t i n g C e r t a i n c r i t e r i a of the u p d a t i n g system were e v o l v e d from a p r e l i m i n a r y study a c c o m p l i s h e d w i t h the h e l p of PCL ( P o o l e C o n s t r u c t i o n L i m i t e d ) . M e e t i n g s w i t h the P r o j e c t Manager and s e v e r a l s i t e v i s i t s p r o v i d e d s u f f i c i e n t background t o g e n e r a t e 58 the b a s i s of the u p d a t i n g p r o c e s s as a p p l i e d i n c o n s t r u c t i o n . A u s e a b l e u p d a t i n g p r o c e d u r e must respond t o the needs of the c o n s t r u c t i o n i n d u s t r y . I t must r e f l e c t ongoing s c h e d u l e p r o g r e s s and p r o v i d e u s e f u l d a t a feedback i n a format t h a t c o n s t r u c t i o n p e r s o n n e l a r e f a m i l i a r w i t h . As such i t s h o u l d u t i l i z e the d a t a and the p r o c e s s by which the i n d u s t r y e f f e c t s c o n t r o l of the p r o j e c t . A u s e a b l e u p d a t i n g p r o c e d u r e must a l s o r e q u i r e m i n i m a l time commitment by the user who does not w i s h t o become a d a t a i n p u t c l e r k . I n p u t s must be l i m i t e d t o t h a t d a t a which cannot be c o l l e c t d by any o t h e r means. Automation of the system must t h e r f o r e be maximized. A c o m p u t e r i z e d u p d a t i n g p r o c e d u r e must u t i l i z e the c a p a b i l i t i e s of a CMIS. I t s a b i l i t y t o c r o s s r e f e r e n c e d a t a can be used t o i n t e g r a t e data from a l l a r e a s of the p r o j e c t e f f e c t e d by changes i n the s c h e d u l e . In summary, the u p d a t i n g p r o c e s s must meet t h r e e s p e c i f i c c r i t e r i a i f i t i s t o a c h i e v e i t s maximum p o t e n t i a l and ensure i t s use by the c o n s t r u c t i o n i n d u s t r y . F i r s t , i t must r e f l e c t the u p d a t i n g p r o c e s s c u r r e n t l y used so as t o respond t o the h e u r i s t i c n a t u r e by which the i n d u s t r y a p p l i e s i t . Second, i t must be s t r e a m l i n e d t o ensure the user i s o n l y r e q u i r e d t o p e r f o r m f u n c t i o n s which cannot be h a n d l e d by the computer so as t o maximize time f o r review and c o n t r o l . T h i r d , i t must e x i s t 59 w i t h i n a CMIS t o u t i l i z e the support c a p a b i l i t y of t h e computer system. A p r o t o t y p e c o n t i n u o u s u p d a t i n g system was d e s i g n e d based on the above t h r e e c r i t e r i a . Input d a t a was m o d e l l e d from d a i l y p r o g r e s s r e p o r t s . Output d a t a was p r e s e n t e d i n a manner f a m i l i a r t o s i t e p e r s o n n e l . A method of p r o v i d i n g a u t o m a t i c network m a n i p u l a t i o n f o r the u p d a t i n g p r o c e s s was added t o m i n i m i z e the user time commitment t o those s i t u a t i o n s w a r r a n t i n g c o n t r o l . M o n i t o r i n g the s c h e d u l e was thus e s s e n t i a l l y a u t o m i z e d . The u p d a t i n g system was i n t e g r a t e d i n t o the s c h e d u l i n g package c o n t a i n i n g the extended v e r s i o n of Laramee's r e p e t i t i v e a c t i v i t y def i n i t i o n . An e x t e n s i v e t e s t i n g of the u p d a t i n g system was performed w i t h the F o u n d a t i o n Company of Canada ( S e c t i o n 2.3.1). O b s e r v a t i o n s from the study f u r t h e r r e i n f o r c e d the c r i t e r i a from which i t was based and p r e s e n t e d a more complete d e f i n i t i o n of the u p d a t i n g r e q u i r e m e n t s of the c o n s t r u c t i o n i n d u s t r y . These o b s e r v a t i o n s a r e p r e s e n t e d below i n the format of the t h r e e c r i t e r i a i n which they were s t u d i e d . 60 3.3 C r i t e r i o n 1: I n t e g r a t i o n I n t o the System A CMIS a l l o w s i n f o r m a t i o n t r a n s f e r from a l l a s p e c t s of the p r o j e c t . T h i s a i d s i n d e c i s i o n making and c o o r d i n a t e s changes i n both c o s t and t i m e . Parameters of such a system were s e t out by P a u l s o n ( R e f e r e n c e 21) from which A.D. R u s s e l l ( R e f e r e n c e 27) l a t e r d e v e l o p e d t h e d e s i g n of a p r o t o t y p e system. A s i m p l i f i e d system i s shown below t o h i g h l i g h t the f l o w of d a t a and i t s a p p l i c a t i o n s ( F i g u r e 3.1). X DECISION / X A N A L Y S I S / U P D A T E \ TIME D A T A CENTRE S C H E D U L E R E P O R T S MONETARY / B I L L I N G CENTRE D A T A F I N A N C I A L R E P O R T S F i g u r e 3.1 S i m p l i f i e d C o n s t r u c t i o n Management I n f o r m a t i o n System The update p r o c e s s must be s u f f i c i e n t t o ensure t h a t the p r o g r e s s of the p r o j e c t i s r e f l e c t e d throughout the CMIS. The 61 major c e n t r e s t o s a t i s f y a r e the Data Base C e n t r e , the Time C e n t r e , and the Monetary C e n t r e . These c e n t r e s must be l i n k e d t o p r o v i d e d a t a a c c e s i b i l i t y and su p p o r t t o the d e c i s i o n making p r o c e s s . L a s t l y , the system must be a b l e t o make a l e g a l s t a n d g i v e n t h a t i t can be c h a l l e n g e d i n c o u r t . W h i l e a l l of the above p o i n t s a re expanded upon below, the t h e s i s i s m a i n l y concerned w i t h the problems of u p d a t i n g w i t h r e s p e c t t o t i m e . The o t h e r a r e a s of a CMIS are i n c l u d e d t o p r o v i d e the reader w i t h a complete scope of the update p r o c e s s . 3.3.1 The Data Base Ce n t r e The d a t a base i s the s t o r a g e a r e a of the CMIS f o r a l l i n f o r m a t i o n p e r t a i n i n g t o p r o j e c t s ongoing and c o m p l e t e d . I d e a l l y , the da t a i s f i l e d u s i n g a s t a n d a r d i z e d code s t r u c t u r e adopted by a l l departments and p r o j e c t s . T h i s ensures c o n t i n u i t y of the knowledge base over t i m e , even i n the event of a change i n p e r s o n n e l . S t a n d a r d i z a t i o n of the code s t r u c t u r e a l s o p e r m i t s a l e a r n i n g p r o c e s s between p r o j e c t s . I n f o r m a t i o n can be a c c e s s e d t o any a s p e c t of the, p r o j e c t i n which d a t a was c o l l e c t e d and s t o r e d . However, i n f o r m a t i o n cannot be u t i l i z e d w i t h o u t c a u t i o n ; i t must be used w i t h i n the c o n t e x t i n which i t was r e c o r d e d . As such, a l l i n f o r m a t i o n s h o u l d be accompanied by a l o g . 62 3.3.1.1 The Log I t i s e s s e n t i a l t h a t a l o g be added t o the d a t a base t o c l a r i f y the s i t u a t i o n i n which d a t a i s r e c o r d e d . T h i s p r e c a u t i o n i s due t o t h e p r o l i f e r a t i o n of v a r i a b l e s t h a t can e f f e c t a p r o j e c t . F or i n s t a n c e : a h i g h p r i c e f o r r e b a r may be due t o a s u p p l i e r monopoly; l i k e w i s e , low p r o d u c t i v i t y i n formwork may be due t o unexpected c o l d weather. Thus, a l o g of s p e c i a l c i r c u m s t a n c e s must be r e c o r d e d i f the d a t a i s t o be u s e f u l f o r f u t u r e r e f e r e n c e . In summary, t o s a t i s f y the l i n k t o the d a t a base, the u p d a t i n g p r o c e s s must work o f f a s t a n d a r d s e t of company codes and use a l o g t o i d e n t i f y the s p e c i f i c p r o j e c t environment a t the time the d a t a was c o l l e c t e d . 3.3.2 The Time C e n t r e The time c e n t r e models the p r o j e c t i n terms of a c t i v i t i e s and t h e i r l o c a t i o n i n t i m e . The update p r o c e s s must p r o v i d e s u f f i c i e n t d a t a t o p o r t r a y the d a i l y p r o g r e s s of these a c t i v i t i e s . T h i s i n c l u d e s a c t u a l s t a r t and f i n i s h d a t e s and "%. c o m p l e t e " i f the a c t i v i t y i s o n g o i n g . The "% complete" r e f e r s t o the p h y s i c a l c o n d i t i o n of the a c t i v i t y ( t h i s w i l l be e x p l a i n e d i n the next s e c t i o n on Cost C e n t r e ) . T h e r e f o r e , t o d e s c r i b e the % complete i n t i m e , which i s needed t o c a l c u l a t e how much l o n g e r the a c t i v i t y w i l l t a k e , a mechanism f o r e s t i m a t i n g the 63 " r e m a i n i n g d u r a t i o n " must a l s o be g i v e n f o r ongoing a c t i v i t i e s . The s t a t u s of procurement a c t i v i t i e s must a l s o be s u p p l i e d f o r ' they have a d i r e c t e f f e c t on the s c h e d u l e of downstream a c t i v i t i e s (Procurement, w h i l e not a major a s p e c t of the t h e s i s , w i l l be expanded upon i n s e c t i o n 3.6.2). E s s e n t i a l t o the c o r r e c t documentation of a p r o j e c t i s the d a i l y s i t e r e p o r t . T h i s can be l a r g e l y performed by the computer through the use of an a u t o m a t i c l o g which d a t e s a l l update e n t r i e s . The user can then complete the l o g by r e c o r d i n g any change o r d e r s i n c u r r e d and the c u r r e n t p r o j e c t environment (weather, equipment a v a i l a b i l i t y e t c ) . Such documentation a l l o w s the user t o s e p a r a t e the cause and e f f e c t of c e r t a i n a c t i v i t y changes i f r e q u i r e d f o r purposes of b i l l i n g , r e p o r t s t o management or l i t i g a t i o n . In summary, t o s a t i s f y the l i n k t o the time c e n t r e , a d a i l y (or any o t h e r p e r i o d deemed u s e f u l ) p r o g r e s s r e p o r t must be i s s u e d , t i e d t o an a u t o m a t i c l o g or d i a r y . T h i s p r o g r e s s d a t a must be s u f f i c i e n t t o ensure u p d a t i n g of the s c h e d u l e , i t must i n c l u d e : a) a c t u a l s t a r t s and f i n i s h e s b) % complete and r e m a i n i n g d u r a t i o n -c) procurement s t a t u s d) change o r d e r s and e) p r e v a i l i n g p r o j e c t c o n d i t i o n s 64 3.3.3 The Monetary C e n t r e I n t e g r a t i o n of the monetary and time c e n t r e s has l o n g been advocated ( R e f e r e n c e s 18 and 21) as i t promotes p a r a l l e l p r o c e s s i n g of t h e s c h e d u l e and c a s h f l o w . The monetary c e n t r e houses two p h i l o s o p h i e s ( p r i c i n g and c o s t i n g ) which a r e viewed as v e r y s e p a r a t e e n t i t i e s by the s c h e d u l e r . The p r i c e c e n t r e i s t i e d d i r e c t l y t o the s c h e d u l e f o r i t d e p i c t s the p r i c e t h a t must be p a i d by the owner f o r each a c t i v i t y performed by the c o n t r a c t o r . P r i c i n g s t r a t e g i e s v a r y w i t h the type of c o n t r a c t ( c o s t - p l u s , lump-sum, u n i t - p r i c e , e t c . ) and a r e e s t a b l i s h e d by the c o n t r a c t o r i n the b i d t o the owner (R e f e r e n c e 2) such as t y i n g a l l c o s t s t o s p e c i f i c m i l e s t o n e s or t o q u a n t i t y measurements. However, d e t a i l e d d i s c u s s i o n of p r i c i n g s t r a t e g i e s i s beyond the scope of t h i s t h e s i s . The c o s t c e n t r e d e p i c t s the c o s t t o the c o n t r a c t o r of c o m p l e t i n g the p r o j e c t . Such c o s t s a r e o f t e n t i e d t o the s c h e d u l e on an a c t i v i t y b a s i s i n the form of manpower and m a t e r i a l s t o p r o v i d e the c o n t r a c t o r w i t h a cash o u t f l o w p r o f i l e of the p r o j e c t . T h i s a l l o w s the c o n t r a c t o r t o p e r f o r m t i m e - c o s t t r a d e o f f s d u r i n g the a n a l y s i s of the v a r i o u s s c e n a r i o s by which he i s a b l e t o c o n s t r u c t the p r o j e c t . I t a l s o p r o v i d e s a mechanism by which t o d e t e r m i n e the impact of change o r d e r s and c l a i m s . 65 The l i n k between the t i m e c e n t r e and the monetary c e n t r e i s u s u a l l y made by the "% c o m p l e t e " d a t a e n t e r e d d u r i n g the update phase. T h i s d e p i c t s the % p h y s i c a l l y complete of the a c t i v i t y as i t i s the p r e f e r r e d measure of payment used by the c o n s t r u c t i o n i n d u s t r y . In summary, t o s a t i s f y the l i n k t o the monetary c e n t r e , c a s h v a l u e s must be t i e d t o the s c h e d u l e a t the a c t i v i t y l e v e l and p r o g r e s s measurement of the p r o j e c t must i n c l u d e a p h y s i c a l measurement of each a c t i v i t y . 3.3.4 The D e c i s i o n Making P r o c e s s A w e l l s t r u c t u r e d CMIS promotes i n f o r m a t i o n f l o w t o a i d the user i n h i s d e c i s i o n s . T h i s i s commonly r e f e r r e d t o as a D e c i s i o n Support System ( R e f e r e n c e 4 ) . In u p d a t i n g , d e c i s i o n a n a l y s i s c o m p r i s e s of the " t r i a l and e r r o r method"; a l t e r n a t i v e s o l u t i o n s a r e d e f i n e d and a n a l y s e d t o compare t h e i r outcome. T h i s h e u r i s t i c approach i s a trademark of the c o n s t r u c t i o n i n d u s t r y . I t s e c l e c t i c n a t u r e makes i t v e r y d i f f i c u l t t o i d e n t i f y a s e t of c o n s i s t a n t v a r i a b l e s by which t o p e r f o r m an o p t i m i z a t i o n r o u t i n e , e s p e c i a l l y i f a l t e r n a t i v e s can . be g e n e r a t e d q u i c k l y by the system. To t h i s end the u p d a t i n g p r o c e s s must a l l o w a "what i f " s t r u c t u r e t o promote i d e a s of the u s e r . The "what i f " s t r u c t u r e must be s u p p o r t e d by i n f o r m a t i o n 66 from a l l a s p e c t s of the p r o j e c t so t h a t a l t e r n a t i v e s can be compared. T h i s i n v o l v e s feedback from a l l t h r e e c e n t r e s of the CMIS. T y p i c a l r e p o r t s i n v o l v i n g the use of time a r e bar c h a r t s , l i n e a r p l a n n i n g c h a r t s , r e s o u r c e p l o t s , network l o g i c and p r o d u c t i v i t y c u r v e s . I t i s i m p o r t a n t t o s t r e s s t h a t no d a t a can be l o o k e d a t i n a vacuum from the r e s t ( R e f e r e n c e 11) f o r a d e c i s i o n u s u a l l y has a r i p p l e e f f e c t throughout the CMIS. I t i s thus e x p e c t e d t h a t a l l s i g n i f i c a n t d e t a i l s of the d e c i s i o n be r e c o r d e d i n the l o g f o r f u t u r e r e f e r e n c e . In summary, t o s a t i s f y the h e u r i s t i c approach t o d e c i s i o n a n a l y s i s , the u p d a t i n g p r o c e s s must p r o v i d e an avenue t o promote a "what i f " approach i n s o l v i n g the sc h e d u l e problems. T h i s avenue must p r o v i d e a c c e s s t o a l l a s p e c t s of the CMIS t o draw on any i n f o r m a t i o n deemed r e l e v e n t . Such "what i f " s t a t e m e n t s , s h o u l d be documented i n the l o g f o r f u t u r e r e f e r e n c e . 3.3.5 L i t i g a t i o n Support I t has l o n g been r e a l i z e d by the c o n s t r u c t i o n i n d u s t r y t h a t a c c u r a t e s y s t e m a t i c r e c o r d s a r e e s s e n t i a l t o p r e s e n t a s u c c e s s f u l case f o r l i t i g a t i o n . Care must be taken t o ensure the CMIS i s s t r u c t u r e d i n a manner a c c e p t a b l e i n c o u r t . C o m p u t e r i z e d C r i t i c a l Path Methods a r e w i d e l y a c c e p t e d by the c o u r t s as a u s e f u l and r e l i a b l e t o o l i n l i t i g a t i o n . However, network a n a l y s i s w i l l not be a c c e p t e d as e v i d e n c e i f i t i s not 67 e x p l i c i t l y t i e d t o p r o j e c t r e c o r d s ( R e f e r e n c e 3 0 ) . Care must a l s o be taken i n the p r e p a r a t i o n of c o m p u t e r i z e d p r i n t o u t as e v i d e n c e . I t i s not c l e a r whether s e c t i o n 30 of the Canada E v i d e n c e A c t (Reference 5) r e g a r d s computer p r i n t o u t as a b u s i n e s s document, even though case h i s t o r i e s have shown a g e n e r a l a c c e p t a n c e of such forms ( R e f e r e n c e 2 4 ) . T h i s problem was r e c e n t l y a d d r e s s e d by the F e d e r a l / P r o v i n c i a l Task F o r c e who p r e p a r e d a r e p o r t on U n i f o r m R u l e s of E v i d e n c e (Reference 25). " A f t e r c o n s i d e r i n g the v a r i o u s a l t e r n a t i v e s , the m a j o r i t y of t h e Task Force recommends t h a t the U n i f o r m E v i d e n c e A c t f o l l o w an i n t e r m e d i a t e c o u r s e (of the s t a t u t o r y p r o v i s i o n s ) , namely, t h a t i n a d d i t i o n t o o t h e r r e q u i r e m e n t s f o r b u s i n e s s documents t h e r e be o n l y t h r e e c o n d i t i o n s of a d m i s s i b i l i t y of computer e v i d e n c e : 1. Proof t h a t the ' d a t a upon which the p r i n t o u t i s based i s of a type r e g u l a r l y s u p p l i e d t o the computer d u r i n g the r e g u l a r a c t i v i t i e s of the o r g a n i z a t i o n from which the p r i n t o u t comes. 2. Proof t h a t the e n t r i e s i n t o the d a t a base from which the p r i n t o u t o r i g i n a t e s were made i n the r e g u l a r c o u r s e of b u s i n e s s ; and 3. P r o o f t h a t the computer program used i n p r o d u c i n g the p r i n t o u t r e l i a b l y and a c c u r a t e l y p r o c e s s e s the d a t a i n the data base." These c o n d i t i o n s s t a t e t h a t the CMIS must be r e l i a b l e and a c c u r a t e . The i n p u t s used f o r e v i d e n c e must p a r a l l e l those which are used r e g u l a r l y i n the c o u r s e of the p r o j e c t . In summary, t o s a t i s f y l i t i g a t i o n s u p p o r t , the u p d a t i n g 68 p r o c e s s must a c q u i r e a l l d a t a t o s u p p o r t i t s c l a i m s d u r i n g i t s r e g u l a r p r o g r e s s measurement. T h i s i n c l u d e s documentation of change o r d e r s . When r e v i s i n g the s c h e d u l e (due t o s i g n i f i c a n t v a r i a n c e of p r o g r e s s from the s c h e d u l e ) , the reason f o r changes must be documented so t h a t user r e a s o n i n g can be l a t e r acknowledged. I n f o r m a t i o n used t o e f f e c t a change must be accompanied by i t s l o g so as t o read d a t a i n a r e l i a b l e and a c c u r a t e f a s h i o n . 69 3.4 C r i t e r i o n 2: The U p d a t i n g P r o c e s s The c o n s t r u c t i o n i n d u s t r y views the u p d a t i n g p r o c e s s as h a v i n g two d i s t i n c t phases: a) A c o n t i n u o u s u p d a t i n g phase b) A r e v i e w and c o n t r o l phase The phases and t h e i r l i n k s t o the CMIS a r e shown i n F i g u r e 3.2. 3.4.1 Phase A P r o g r e s s measurement i s i n p u t on a d a i l y b a s i s t o ensure c l o s e m o n i t o r i n g and documentation of the p r o j e c t . An update a n a l y s i s , prompted by the u s e r , i s u s u a l l y performed on a p e r i o d i c b a s i s when the net e f f e c t of p r o g r e s s of the s c h e d u l e i s c o n s i d e r e d worthy of n o t i n g . However, an a n a l y s i s can be prompted a t any time the user c o n s i d e r s i t b e n e f i c i a l . T h i s a l l o w s new d a t a to be a n a l y s e d q u i c k l y i f i t i s b e l i e v e d t o d i s t u r b the l a t e s t s c h e d u l e , y e t p e r m i t s unimpeded t r a c k i n g of the p r o j e c t when p r o g r e s s conforms t o the s c h e d u l e . The outcome of the a n a l y s i s i s p r o v i d e d i n terms of the updated s c h e d u l e , p r o g r e s s r e p o r t s and any o t h e r d a t a the u s e r may wish t o use. From the s e r e p o r t s the u s e r can d e c i d e i f the s c h e d u l e i s under c o n t r o l . I f the answer i s y e s , the c y c l e i s r e p e a t e d . I f the answer i s no, the u s e r must e n t e r the r e v i e w 70 DAILY PROGRESS DATA 8" i o E o Actual Starts and Finishes % Complete & Remoining Duration Scheduled Start Dates Procurement Status Change Orders Prevailing Project Conditions UPDATE DATA BASE — » U P D A T E A N A L Y S I S PROMPTED BY USER Updated Schedule Progress Status Reports Other Data IIIIIIIIHIIIIIHtllllMliniHIIIMIIIIMIIIIIIIUIinillfH^ I .4 I I I Monetary Analysis Time Analysis Other Data Y E S NO EFFECT CONTROL Y E S Document Decision Rationale Release .*] Revised Schedule c a in 3 O a o u I < UJ < z Q. I o O u a> > oc I CD UJ < F i g u r e 3.2 The U p d a t i n g P r o c e s s F l o w c h a r t 71 and c o n t r o l s t a g e . 3.4.2 Phase B At some p o i n t i n time, i t i s imminent t h a t the s c h e d u l e , which i s based on a s t a t i c model, w i l l no l o n g e r r e f l e c t t he dynamics of the p r o j e c t . T h i s i s o f t e n due t o an i n c r e a s i n g v a r i a n c e between p r o g r e s s r e p o r t s and s c h e d u l e d a c t i v i t i e s . I t can a l s o be due t o c o n s t r a i n t s which d i d not e x i s t or were not r e a l i z e d a t the time the schedule was implemented, such as change o r d e r s or new e s t i m a t e s of a c t i v i t y d u r a t i o n s . At t h i s p o i n t , i t i s time t o r e v i e w , e f f e c t c o n t r o l and r e l e a s e a r e v i s e d s c h edule which, g i v e n the new c o n s t r a i n t s of the problem, once a g a i n p r o j e c t s an a c c e p t a b l e outcome. A h e u r i s t i c a n a l y s i s or m u l t i p l e s c e n a r i o approach i s adopted i n o r d e r t o f i n d the most a p p r o p r i a t e r e v i s i o n s . The a n a l y s i s draws on a l l c a p a b i l i t i e s of the CMIS t o t r a d e o f f v a r i a b l e s of money and time t o a c h i e v e a s a t i s f a c t o r y outcome. Once the p r e f e r r e d s c h e d u l e has been d e c i d e d and r e a s o n i n g f o r the c h o i c e documented, a r e v i s e d s c h e d u l e i s r e l e a s e d . 72 3.4.3 Schedule I n t e r a c t i o n I t i s i m p o r t a n t t o note the r o l e of each phase and i t s e f f e c t on the s c h e d u l e . The r o l e of Phase A i s p r i m a r i l y the c o l l a t i o n of update m a t e r i a l . I t i s c o n s i d e r e d p a r t of the d a i l y s i t e r o u t i n e and can be performed by most s i t e p e r s o n n e l . Such work r e q u i r e s no d i r e c t i n t e r a c t i o n w i t h the s c h e d u l e . Phase B performs the r o l e of d a t a a n a l y s i s . T h i s can r e q u i r e e x t e n s i v e i n t e r a c t i o n w i t h the schedule t o respond t o the update c o n d i t i o n s . Such d e c i s i o n making i s u s u a l l y h a n d l e d by peop l e a u t h o r i z e d t o a l l o c a t e company r e s o u r c e s i n response t o sc h e d u l e updates. In summary, the u p d a t i n g f l o w c h a r t must p r o v i d e the s e g r e g a t i o n of d a t a c o l l a t i o n and d a t a a n a l y s i s . T h i s e f f e c t i v e l y l i m i t s d i r e c t s c h e d u l e i n t e r a c t i o n t o a u t h o r i z e d p e r s o n n e l and p e r m i t s d a t a c o l l e c t i o n t o p r o c e e d u n h i n d e r e d u n t i l a r e v i e w and subsequent c o n t r o l of the p r o j e c t i s r e q u i r e d . T h e r e f o r e : a) I t must p r o v i d e a two t i e r system by which a s c h e d u l e can be c o n t i n u o u s l y updated and, when n e c e s s a r y , r e v i s e d . b) Both phases must p r o v i d e f u l l p o t e n t i a l f o r i n p u t and documentation. Both phases must a l l o w f u l l a c c e s s t o the CMIS f o r p r o j e c t s t a t u s r e p o r t s and, i n the case of phase B, f o r a l t e r n a t i v e a n a l y s i s of time and money. Phase B must p r o v i d e a h e u r i s t i c d e c i s i o n making c a p a b i l i t y by p r o v i d i n g a " l o o p " i n the f l o w c h a r t t o r e v i e w a l t e r n a t i v e p r o c e d u r e s . 74 3.5 C r i t e r i o n 3: Automation of the U p d a t i n g P r o c e s s The c o n t i n u o u s u p d a t i n g phase r e q u i r e s an a l g o r i t h m t h a t can update a s c h e d u l e and fee d a l l a s p e c t s of the CMIS as each p e r i o d of p r o g r e s s measurement i s i n p u t . T h i s must be done w i t h minimum work by the user as the f u n c t i o n i s merely t o t r a c k p r o g r e s s a g a i n s t the sc h e d u l e and p o r t r a y the t i m i n g of the r e m a i n i n g a c t i v i t i e s . S i n c e the l o g i c f o r the sc h e d u l e has a l r e a d y been d e f i n e d by the u s e r , the a l g o r i t h m has a data base from which t o draw a l l n e c e s s a r y d a t a t o pe r f o r m t h i s t a s k automat i c a l l y . The c o n t i n u o u s u p d a t i n g a l g o r i t h m has not been f e a s i b l e i n p r a c t i c e ( Reference 11) due t o : a) The h i g h c o s t of m a i n t a i n i n g computer programs. b) Problems of r e a r r a n g i n g network l o g i c a s s o c i a t e d w i t h such changes. Computer t e c h n o l o g y has e f f e c t i v e l y e l i m i n a t e d the problems of computer c o s t . However, the m a n i p u l a t i o n of l o g i c l i n k s i s s t i l l l e f t t o the user who must review the network each time p r o g r e s s d a t a v a r i e s from the sequence of the s c h e d u l e , thus m a i n t a i n i n g a h i g h p e r s o n n e l c o s t . The author has deve l o p e d a c o n t i n u o u s u p d a t i n g a l g o r i t h m which d e t e c t s sequence changes and a d j u s t s the r e m a i n i n g a c t i v i t i e s a c c o r d i n g l y ( T h i s a l g o r i t h m i s d e f i n e d i n t h e next s e c t i o n ) . T h i s e f f e c t i v e l y e l i m i n a t e s any user i n p u t beyond the i n p u t of p r o g r e s s d a t a , except when c o r r e c t i v e a c t i o n 75 must be i n i t i a t e d . In summary, the c o n t i n u o u s u p d a t i n g phase must adopt an a l g o r i t h m which can s u p p o r t a CMIS and update the s c h e d u l e f o r each p e r i o d of p r o g r e s s measurement, u s i n g no time commitment by the us e r o t h e r than t h a t of d a i l y p r o g r e s s r e p o r t s . 76 3.6 The Co n t i n u o u s U p d a t i n g A l g o r i t h m The aim of t h i s s e c t i o n i s t o d e s c r i b e the c o n t i n u o u s u p d a t i n g a l g o r i t h m t h a t was used i n the p r o t o t y p e system t o f u r t h e r study the u p d a t i n g p r o c e s s . I t was found t o respond w e l l t o changes i n the s c h e d u l e and s u p p l i e d an ongoing p i c t u r e of work p r o g r e s s . The study showed the a l g o r i t h m t o be both r o b u s t and r e a l i s t i c i n i t s approach t o m o n i t o r i n g and c o n t r o l l i n g the p r o j e c t . C o ntinuous u p d a t i n g r e q u i r e s a mechanism which can span the p a s t and f u t u r e t o c r e a t e a s i n g l e network. I t must be a b l e t o d e t e c t sequence v a r i a t i o n s between the program d a t a ( p a s t t e n s e ) and the sc h e d u l e ( f u t u r e t e n s e ) and make a p p r o p r i a t e network a d j u s t m e n t s t o m a i n t a i n the network i n t e g r i t y . These a d j u s t m e n t s a r e u s u a l l y made ma n u a l l y by the user each time the s c h e d u l e i s updated. T h i s e s s e n t i a l l y i s the " b r i d g e " which spans the t e n s e s and a l l o w s the s c h e d u l e t o respond t o the p r o g r e s s d a t a . The a l g o r i t h m p r o p o s e s a d e f i n i t i o n of the p r i n c i p l e s by which the us e r a d j u s t s the network. By a d o p t i n g these p r i n c i p l e s i t i s p o s s i b l e f o r t h e a l g o r i t h m t o make the a p p r o p r i a t e a d j u s t m e n t s and hence p e r f o r m the update a u t o m a t i c a l l y . B e f o r e l o o k i n g a t the network a d j u s t m e n t s r e q u i r e d f o r u p d a t i n g i t i s f i r s t n e c e s s a r y t o review s c h e d u l i n g t h e o r y and i n t r o d u c e some new d e f i n i t i o n s t h a t u p d a t i n g imposes. 77 3.6.1 The A c t i v i t y Window L o g i c l i n k s used by s c h e d u l i n g t h e o r y d e f i n e t h e boundaries of time t h a t each a c t i v i t y can be exe c u t e d w h i l s t m a i n t a i n i n g t h e p r o j e c t d u r a t i o n . In e s s e n c e , l o g i c c r e a t e s each a c t i v i t y ' s window, bound on the l e f t by i t s p r e d e c e s s o r s and bound i n the r i g h t by i t s s u c c e s s o r s as shown i n F i g u r e 3.3. I t s p r e d e c e s s o r s S S , F S 4 |_ 55 S F , F F < | ~ CSSLD F i g u r e 3.3 The A c t i v i t y Window and I t ' s L o g i c L i n k s d etermine how e a r l y the a c t i v i t y can s t a r t w i t h o u t b r e a k i n g the p r e d e c e s s o r l o g i c . T h i s i s the o p e r a t i o n known as the Forward P a s s . I t s s u c c e s s o r s determine how l a t e the a c t i v i t y can f i n i s h w i t h o u t b r e a k i n g the s u c c e s s o r l o g i c . T h i s o p e r a t i o n i s known as the Backward P a s s . J + S S . S F F S , F F HI?® 78 3.6.2 The A c t i v i t y D u r a t i o n s I t i s no l o n g e r p o s s i b l e t o c l a s s i f y a l l a c t i v i t i e s under " s c h e d u l e d " ; d e n o t i n g t h a t they are t o happen i n the f u t u r e t e n s e . I t i s now p o s s i b l e t o have t h r e e c l a s s i f i c a t i o n s of a c t i v i t i e s ( F i g u r e 3.4): a) The Completed A c t i v i t y b) The Ongoing A c t i v i t y c) The Scheduled A c t i v i t y COMPLETED A C T U A L D U R A T I O N TTGDITO 1 R E M A I N I N G I D U R A T I O N 0 H G D M 6 P R O J E C T E D A C T U A L D U R A T I O N S C H E D U L E D D U R A T I O N F i g u r e 3.4 Three Types of A c t i v i t i e s and T h e i r D u r a t i o n s The Completed A c t i v i t y , as the name s u g g e s t s , denotes t h a t i t s d u r a t i o n was s t a r t e d and f i n i s h e d w i t h i n the P a s t Time Zone. Thus, i t has an A c t u a l D u r a t i o n ( t h e span of time i n which the a c t i v i t y was a c t u a l l y p e r f o r m e d ) . The Ongoing A c t i v i t y has a d u r a t i o n which s t a r t e d i n the P a s t Time Zone and extends i n t o 79 the F u t u r e Time Zone. The amount of time r e m a i n i n g t o f i n i s h the a c t i v i t y i s c a l l e d the Remaining D u r a t i o n . The T o t a l D u r a t i o n of the whole a c t i v i t y over both time zones i s c a l l e d the P r o j e c t e d A c t u a l D u r a t i o n . The Scheduled A c t i v i t y i s t o t a l l y w i t h i n the F u t u r e Time Zone, t h e r e f o r e i t i s a l r e a d y d e f i n e d by s c h e d u l i n g t h e o r y . The d u r a t i o n has both a s c h e d u l e d s t a r t and a s c h e d u l e d f i n i s h , as such i t i s c a l l e d the Scheduled D u r a t i o n . 3.6.3 The A c t i v i t y S t a r t s and F i n i s h e s The s t a r t s and f i n i s h e s of a c t i v i t i e s must a l s o be r e d e f i n e d when u p d a t i n g (see F i g u r e 3.5). A S D A F D | t i i t t i t i i i ONBOING A S D m E F D | L F D | SCHEDULED 1 E S D E F D | L S D L F D F i g u r e 3.5 S t a r t and F i n i s h D e f i n i t i o n s and T h e i r Time Zones For a completed a c t i v i t y , the a c t u a l s t a r t and f i n i s h a r e known; they a r e e v e n t s which have taken p l a c e , and are c a l l e d 80 the A c t u a l S t a r t Date (ASD) and the A c t u a l F i n i s h Date (AFD) of the a c t i v i t y . For an Ongoing A c t i v i t y , i t s d u r a t i o n has a l s o s t a r t e d , t h e r e f o r e i t too w i l l have an A c t u a l S t a r t Date. However, the Ongoing A c t i v i t y has not y e t been completed; i t i s s t i l l unknown where e x a c t l y i t w i l l end i n the F u t u r e Time Zone. T h i s i s the t y p i c a l s i t u a t i o n i n s c h e d u l i n g t h e o r y and thus i t w i l l be g i v e n an E a r l y F i n i s h Date (EFD) and a L a t e F i n i s h Date (LFD) based on i t s r e m a i n i n g d u r a t i o n . The Scheduled A c t i v i t y which has not y e t begun w i l l not have a f i x e d b e g i n n i n g or end, t h e r e f o r e s c h e d u l i n g t h e o r y r u l e s i t w i l l have an E a r l y S t a r t Date (ESD) , a L a t e S t a r t Date (LSD) an E a r l y F i n i s h Date and a L a t e F i n i s h Date. 3.6.4. S u b s t a n t i a l C o m p l e t i o n V e r s e s T o t a l C o m p l e t i o n C o m p l e t i n g an a c t i v i t y i s not always a s i m p l e c a s e . An a c t i v i t y may be 95% complete but r e q u i r e extended time t o p e r f o r m the l a s t 5% due t o a few m i s s i n g items (eg. a p l u g f o r the s i n k ) . C l e a r l y t h i s a c t i v i t y i s not t o t a l l y c o m p l e t e , y e t n e i t h e r i s i t l i k e l y t o h o l d up any a c t i v i t y downstream. T h e r e f o r e , f o r s c h e d u l i n g purposes t h e a c t i v i t y has been S u b s t a n t i a l l y Completed and can be g i v e n an A c t u a l F i n i s h Date. To denote t h a t the a c t i v i t y i s not y e t T o t a l l y Complete, a "% c o m p l e t e " ( i e . 95%) i s added t o the update d a t a base f o r use i n the monetary c e n t r e as b i l l i n g d a t a or i n the d a t a base c e n t r e f o r r e p o r t s . 81 3.6.5 Procurement As procurement i s e s s e n t i a l t o the p r o g r e s s of the a c t i v i t i e s i t s u p p l i e s , i t seems r e a s o n a b l e t o make a d i r e c t l i n k between procurement and the a c t i v i t i e s i n the s c h e d u l e . Thus any d e l a y or advance i n procurement would be r e f l e c t e d i n the s c h e d u l e . However, the c o n s t r u c t i o n i n d u s t r y i s not unanimous i n t h i s d e c i s i o n . W h i l e procurement i s d e f i n i t e l y - c o nnected t o the s c h e d u l e , c o n s t r u c t i o n p e r s o n n e l do not t h i n k i t i s d i r e c t . T h i s i s based on the view t h a t procurement i s e x t e r n a l t o the p r o j e c t u n t i l i t s d e l i v e r y on s i t e . I t i s a l s o c h a r a c t e r i z e d by l o n g l e a d t imes t o a l l o w f o r m a n u f a c t u r i n g and t r a n s p o r t a t i o n making i t d i f f i c u l t t o m o n i t o r c l o s e l y . The p r o c e s s i s o f t e n undertaken by a d m i n i s t r a t i v e p e r s o n n e l from head o f f i c e and hence i s not under the c o n t r o l of s i t e p e r s o n n e l . Based on the view of the c o n s t r u c t i o n i n d u s t r y , procurement has been i n d i r e c t l y l i n k e d t o the s c h e d u l e by c a l c u l a t i n g the l e a d time needed from the date i t i s r e q u i r e d on s i t e . By l i n k i n g i t i n t h i s manner, a change i n the d e l i v e r y date of m a t e r i a l s does not a u t o m a t i c a l l y e f f e c t the s c h e d u l e . However, i f the user wishes to l e t the procurement e f f e c t be seen, a s c h e d u l e s t a r t date can be imposed d i r e c t l y t o the a c t i v i t y af f e c t e d . 82 3.6.6 The H i e r a r c h i c a l S t r u c t u r e of L i n k s We now have f o u r p o s s i b l e s e t s of d a t a t h a t must be kept f o r an U p d a t i n g S c h e d u l i n g A l g o r i t h m . These s e t s of d a t a , shown i n T a b l e 3.1, must be p r i o r i z e d i f one i s t o e x p e c t the network t o b r i d g e the gap between time zones. The f o l l o w i n g system i s s u g g e s t e d . E S D E F D L S D L F D S S D S F D A S D A F D T r a d i t i o n a l S c h e d u l i n g D e f i n e s w i n d o w f o r e a c h a c t i v i t y . D e f a u l t s t o E S D u n l e s s s p e c i f i c d a t e i s e n t e r e d . R e c o r d s a c t i v i t y p r o g r e s s i o n . T a b l e 3.1 The Four S e t s of Data R e q u i r e d For U p d a t i n g The ESD, EFD, LSD, LFD a r e the b a s i s of the network d e r i v e d by S c h e d u l i n g Theory t o d e p i c t the windows i n the F u t u r e Time Zone f o r each a c t i v i t y . However, i t does not i n v o k e a f i x e d s t a r t or f i n i s h f o r any a c t i v i t y . The S c h e d u l e d S t a r t and i t s r e l a t e d Scheduled F i n i s h do i n v o k e a f i x e d q u a n t i t y which can more c l e a r l y d e f i n e the p l a c i n g of t h a t a c t i v i t y i n t i m e . As such, the SSD and SFD must o v e r u l e the E a r l y c o u n t e r p a r t s f o r they reduce the u n c e r t a i n t y of the s c h e d u l e ( I n the c o n s t r u c t i o n 83 i n d u s t r y , i f no Scheduled S t a r t Date i s imposed, i t i s commonly assumed t o be t h e same as the ESD). In t u r n , the A c t u a l S t a r t and F i n i s h D ates must o v e r r u l e the S c h e d u l e d c o u n t e r p a r t s f o r they a r e the a c t u a l q u a n t i t y t h a t o c c u r e d . T h i s system i s summarized below i n Table 3.2 as the H i e r a r c h i c a l S t r u c t u r e of L i n k s . S T A R T F I N I S H M O S T C E R T A I N A S D A F D S S D S F D L E A S T 1 : E R T A I N E S D , L S D E F D , L F D T a b l e 3.2 The H i e r a r c h i c a l S t r u c t u r e of L i n k s 84 3.6.7. The V a l i d i t y of L o g i c L i n k s W i t h the new d e f i n i t i o n s of u p d a t i n g now i n p l a c e , i t i s time t o l o o k a t the network a d j u s t m e n t s t h a t a r e r e q u i r e d t o pe r f o r m a u t o m a t i c u p d a t i n g . S c h e d u l e s a r e h e l d t o g e t h e r by l o g i c l i n k s which the s c h e d u l e r b e l i e v e s d e p i c t s the p h y s i c a l c o n s t r a i n t s of the p r o j e c t . For example; a l l o w i n g the c o n c r e t e t o s e t f o r t h r e e days b e f o r e s t r i p p i n g the forms would be o u t l i n e d as shown i n F i g u r e 3.6 w i t h the c o n s t r a i n t b e i n g m o d e l l e d as an FS l i n k of t h r e e days. What would happen t o the s c h e d u l e i f the forms were POUR CONCRETE FS = 3 w S T R I P FORMS t t t t [ j t t V F i g u r e 3.6 Example of C o n s t r a i n t M o d e l l e d as a L o g i c L i n k s t r i p p e d o n l y two days a f t e r the c o n c r e t e was poured due t o a newly adopted c u r i n g t e c h n i q u e ? T h i s , g i v e n the network l o g i c i s not f e a s i b l e , y e t i t has a c t u a l l y o c u r r e d and i s t h e r e f o r e a j u s t i f i a b l e statement t o make when u p d a t i n g . I t i s t h e r e f o r e n e c e s s a r y t o examine l o g i c l i n k s d u r i n g the u p d a t i n g phase and deter m i n e i f they a re s t i l l v a l i d . 85 L o g i c l i n k s t h a t do not conform t o the p r o g r e s s d a t a a r e c o n s i d e r e d n o n - v a l i d . These l i n k s a re by-passed by the Forward and Backward Pass but a r e not d e l e t e d . They are kept t o ensure t h a t a t l e a s t one s u c c e s s o r and one p r e d e c e s s o r e x i s t f o r every a c t i v i t y t o p r o v i d e a complete l o g i c network. They a r e a l s o u s e f u l as a f l a g t o show d e v i a t i o n s from the s c h e d u l e i n c l a i m s i t u a t i o n s and management r e p o r t s . I t i s not p o s s i b l e f o r the computer t o t a k e the u s e r ' s new data and t r a n s f o r m i t i n t o new l o g i c l i n k s ( e x c e p t f o r the s i t u a t i o n of ongoing a c t i v i t i e s w hich w i l l be d i s c u s s e d l a t e r i n the c h a p t e r ) . However, by m a i n t a i n i n g the i n t e g r i t y of the network t h i s f u n c t i o n i s not e s s e n t i a l t o p e r f o r m i n g the c o n t i n u o u s update phase. New l o g i c l i n k s , i f any, a r e l e f t t o the user t o i n s e r t when the a u t h o r i z e d p e r s o n n e l deems a r e v i e w of the network i s i n o r d e r . The v a l i d i t y of each l i n k a g e type can be c h a r a c t e r i z e d f o r a l l t h r e e t y p e s of a c t i v i t i e s . Each a c t i v i t y window i s d e s c r i b e d below w i t h i t s v a l i d l i n k s . N o n - v a l i d l i n k s a r e a l s o shown: d e p i c t e d by a s l a s h t h r o u g h the d a t e (e.g. A#5 = a n o n - v a l i d ASD l i n k ) . 86 3.6.8. The Completed A c t i v i t y and i t s L o g i c L i n k s The s u c c e s s o r and p r e d e c e s s o r l i n k s d e f i n e the window i n which an a c t i v i t y might o c c u r . S i n c e the a c t i v i t y has a l r e a d y o c c u r e d , i t s window i s d e f i n e d by t h e a c t i v i t y ' s A c t u a l S t a r t and A c t u a l F i n i s h Dates. Thus, the v a l i d i t y of l i n k s t o and from the a c t i v i t y do not a f f e c t i t s placement i n time s i n c e no Forward and Backward Pass are performed on a Completed A c t i v i t y . 3.6.9 The S c h e d u l e d A c t i v i t y and i t s L o g i c L i n k s The v a l i d i t y of each l i n k f o r the S c h e d u l e d A c t i v i t y i s p r e s e n t e d i n ' F i g u r e 3.7 f o r b o t h the Forward and Backward P a s s . The Forward Pass of a S c h e d u l e d A c t i v i t y i s v e r y s i m p l e . The p r e d e c e s s s o r l i n k s must always be j o i n e d w i t h the l a t e s t and most up t o d a t e i n f o r m a t i o n as t h i s w i l l ensure the most p r o b a b l e s c h e d u l e i s f o l l o w e d . T h i s r e l a t i o n s h i p i s found by u s i n g the H i e r a r c h i c a l S t u c t u r e of L i n k s t o p r o v i d e the e a r l i e s t s t a r t based on the known c o n s t r a i n t s , i n c l u d i n g those t h a t have become a p p a r e n t d u r i n g the update phase. For example; the e a r l y s t a r t may s u g g e s t t h a t the s c h e d u l e d a c t i v i t y s t a r t on the f i r s t day of the w o r k i n g week. However, a d e l a y i n m a t e r i a l s might have i n v o k e d a Scheduled S t a r t Date two days l a t e r ( n o t e , SSD has been i n p u t d i r e c t l y by the user i n view of l a t e p r o c u r e m e n t ) . G i v e n t h i s s e t of c i r c u m s t a n c e s , i t would be i r r a t i o n a l t o s c h e d u l e t h a t a c t i v i t y t o s t a r t on the f i r s t day 87 ASD>SSD>E5D AFD>SFD>EFD SCHEDULED A = f i r g » A—| i S F FF SSD>LSD SFD>LFD F i g u r e 3.7 Forward and Backward Pass of a Scheduled A c t i v i t y when new i n f o r m a t i o n p h y s i c a l l y d e f a u l t e d i t s s t a r t by two days. L i k e w i s e , an A c t u a l S t a r t Date o v e r u l e s any o t h e r S t a r t Date due t o i t b e i n g the t r u e s t a r t of the a c t i v i t y . The Backward Pass of a Scheduled A c t i v i t y demands a l i t t l e more i n s i g h t i n t o the e f f e c t of s u c c e s s o r a c t i v i t i e s . As i n the Forward Pass i t i s i m p o r t a n t t o make the s u c c e s s o r c o n n e c t i o n w i t h t h e l a t e s t and t h e r e f o r e most c e r t a i n d a t a . T h i s would suggest the H i e r a r c h i c a l S t r u c t u r e of L i n k s w i t h two e x c e p t i o n s . 1) I f t h e s u c c e s s o r , f o r whatever r e a s o n , was found t o have a c t u a l l y been s t a r t e d , t h e l o g i c l i n k i s no l o n g e r v a l i d . T h i s can be e a s i l y demonstrated i n the example shown i n F i g u r e 3.8. Whereas i t i s good p r a c t i c e t o p a i n t the w a l l s of a room b e f o r e 88 P R E D E C E S S O R S SUCCESSORS ::i;:|i-:l::::t:::t P L A C E C A R P E T S U C C E S S O R S > t it i t i i> i ti it t* i i P L A C E C A B P E T I P R E D E C E S S O R S P A I N T W A L L S ; 1 [TH/S I I MIC IS BROKE* AS IT IS MOM-VALID _| F i g u r e 3.8 . I n v a l i d a t i o n of Suc c e s s o r L i n k s w i t h an A c t u a l S t a r t Date p l a c i n g the c a r p e t so t h a t t h e r e i s no chance of s p i l l i n g p a i n t , i t may be p o s s i b l e t h a t the p a i n t e r i s u n a v a i l a b l e . In t h i s case i t would be a d v i s a b l e t o l a y the c a r p e t f i r s t and to p r o t e c t i t when the p a i n t e r r e t u r n s t o the j o b . T h e r e f o r e , s u c c e s s o r l i n k s w i t h an A c t u a l S t a r t are no l o n g e r v a l i d . 2) The o t h e r e x c e p t i o n i n v o l v e s making a l o g i c l i n k i n v a l i d i f the s u c c e s s o r has a l r e a d y f i n i s h e d . A s i m i l a r example (see F i g u r e 3.9) demonstrates t h i s p o i n t . P r a c t i c e would suggest t h a t the p a i n t e r f i n i s h p a i n t i n g w a l l s of each room b e f o r e the l i g h t s w i t c h p l a t e s a r e a l l a f f i x e d t o a v o i d p a i n t on the s w i t c h p l a t e s . However , i f the p a i n t e r i s u n a v a i l a b l e , the l i g h t s w i t c h p l a t e s c o u l d be f i n i s h e d f i r s t . T h i s w i l l of c o u r s e make the p a i n t e r s j o b a l i t t l e more d i f f i c u l t as he must now p a i n t 89 SUCCESSORS P R E D E C E S S O R S i i t , . , PAINT WAILS • LIGHT S W I T C H P L A T E S FF § P R E D E C E S S O R S LIGHT S W I T C H P L A T E S PAINT WAILS THIS L INK IS BROKEN AS IT IS NON- VAL tD S U C C E S S O R S i j F i g u r e 3.9 I n v a l i d a t i o n of S u c c e s s o r L i n k s w i t h an A c t u a l F i n i s h Date c a r e f u l l y around the p l a t e s , but i t does a l l o w the p r o j e c t t o s t a y on s c h e d u l e . In t h i s c a s e , s u c c e s s o r l i n k s w i t h an A c t u a l F i n i s h a re no l o n g e r v a l i d . I f the S c h e d u l e d A c t i v i t y had o n l y one s u c c e s s o r , and t h i s l i n k was d e c l a r e d n o n - v a l i d , i t would f l o a t t o the end of the p r o j e c t . At t h i s p o i n t the user must d e c i d e i f the f l o a t i s r e a l i s t i c . I f i t i s n o t , the user can e i t h e r l e a v e i t w i t h the knowledge t h a t the a c t i v i t y i s soon t o be performed and hence the f l o a t w i l l d i s a p p e a r , or the s c h e d u l e can be r e v i e w e d and the a c t i v i t y t i e d t o a new p r e d e c e s s o r . E x p e r i e n c e on s i t e has shown t h a t the f l o a t 'is u s u a l l y n e g l e c t e d u n l e s s the a c t i v i t y i s b e i n g c l o s e l y m o n i t o r e d . 90 3.6.10 The Ongoing A c t i v i t y and i t s L o g i c L i n k s The Ongoing A c t i v i t y p r e s e n t s a s p e c i a l case as i t spans the p a s t and f u t u r e . S i n c e the a c t i v i t y has been s t a r t e d , i t f o l l o w s t h a t i t s r e m a i n i n g d u r a t i o n be a l l o w e d t o c o n t i n u e i t s p r o g r e s s . The completed p o r t i o n of the Ongoing A c t i v i t y does not need t o be s c h e d u l e d as i t has a l r e a d y been f i x e d i n time ( S e c t i o n 3.6.8). However, the Remaining D u r a t i o n must undergo a Forward and Backward Pass i n o r d e r t o c a l c u l a t e i t s f l o a t . Given t h e above argument, i t i s r e a s o n a b l e t o assume t h a t the Remaining D u r a t i o n may not have t o be performed i m m e d i a t e l y ( i . e . user may w i s h to use up some of i t ' s f l o a t , or i t may have a l o g i c l i n k which w i l l d e l a y i t s e a r l i e s t f i n i s h ) . T h i s i s not c o n s i d e r e d a d i s c o n t i n u i t y i n the a c t i v i t y , i t i s merely a p e r i o d of z e r o p r o d u c t i v i t y . T h i s argument i s s t r e n g t h e n e d by the d e f i n i t i o n of A c t u a l D u r a t i o n i n S e c t i o n 3.6.2 ( A c t u a l D u r a t i o n = A c t u a l F i n i s h - A c t u a l S t a r t ) which l e n d s no credence t o i t s p r o d u c t i v i t y r a t e w i t h t i m e . A g e n e r a l r u l e of thumb t o remember f o r the H i e r a r c h i c a l S t r u c t u r e of L i n k s of Ongoing A c t i v i t i e s i s t h a t i t i s based on the Scheduled A c t i v i t y . T h i s can c l e a r l y be seen by a d i r e c t comparison of diagrams f o r the Forward and Backward Pass of the Remaining D u r a t i o n p o r t i o n of the Ongoing A c t i v i t y ( F i g u r e 3.10) w i t h t h a t of F i g u r e 3.7. The Ongoing A c t i v i t y does have c e r t a i n c h a r a c t e r i s t i c s of 91 ASD>SSD>ESD TNOW AFD>SFD>EFD r---I • I i L... — I — • A S 0 SSD>LSD FF = 1 — > A S4^! \f4 SFD>LFD s F i g u r e 3,10 Forward and Backward Pass of the Ongoing A c t i v i t y i t s own r e g a r d i n g the v a l i d i t y of l o g i c l i n k s . D u r i n g the Forward P a s s , the Remaining D u r a t i o n has no p r e d e c e s s o r l i n k s t i e d t o i t s s t a r t ( P r e d e c e s s o r l i n k s from o t h e r a c t i v i t i e s t i e d t o the A c t u a l S t a r t of the Ongoing A c t i v i t y do not a f f e c t i t s p l a c e m e n t ) . The p o s s i b i l i t y can t h e r e f o r e a r i s e of a Remaining D u r a t i o n which has no p r e d e c e s s o r s a t a l l (The Ongoing A c t i v i t y may not have r e q u i r e d any SF or FF l i n k s ) . T h i s would a l l o w the Remaining D u r a t i o n t o have an E a r l y S t a r t Date a t the b e g i n n i n g of the p r o j e c t . T h i s i s p r e v e n t e d by g i v i n g the a c t i v i t y a new p r e d e c e s s o r s t a t i n g t h a t the Remaining D u r a t i o n can s t a r t no e a r l i e r than the next w o r k i n g day on the job ( i . e . TNOW). The Backward Pass f a c e s a s i m i l a r s i t u a t i o n . The Remaining D u r a t i o n does not have any s u c c e s s o r l i n k s t i e d t o the i t s 92 s t a r t . As such, the o n l y s u c c e s s o r l i n k s a r e a t t a c h e d t o i t s F i n i s h (FS and FF l i n k s ) . As i n the case of the Sche d u l e d A c t i v i t y , l i n k s i n v o l v i n g an ASD or AFD of the s u c c e s s o r a re n o n - v a l i d (see F i g u r e s 3.8 and 3.9). Given t h a t the Remaining D u r a t i o n has a l l of i t s s u c c e s s o r s d e c l a r e d n o n - v a l i d , i t would f l o a t t o the end of the p r o j e c t . Once a g a i n i t i s up t o the user t o d e c i d e what must be done i f t h i s c o n d i t i o n a r i s e s . 3.6.11 Summary By a d o p t i n g the H i e r a r c h i c a l S t r u c t u r e of L i n k s i t i s p o s s i b l e t o promote an a u t o m a t i c u p d a t i n g procedure based on the most up-to-date s c h e d u l e i n f o r m a t i o n . The c o n t i n u o u s u p d a t i n g a l g o r i t h m does not p r o f e s s t o o p t i m i z e the network. I t s purpose i s t o m a i n t a i n network i n t e g r i t y so t h a t the e f f e c t of update d a t a can be a u t o m a t i c a l l y d i s p l a y e d , t h u s p e r f o r m i n g Phase A of the u p d a t i n g p r o c e s s d e f i n e d i n S e c t i o n 3.4.1. I f the e f f e c t of the update i s not s a t i s f a c t o r y t o the u s e r , the sc h e d u l e can be revi e w e d and the a p p r o p r i a t e changes made, a l l o w i n g the user t o m a i n t a i n d i r e c t c o n t r o l of the s c h e d u l e as d e f i n e d i n Phase B of the u p d a t i n g p r o c e s s , S e c t i o n 3.4.2. 93 3.7 U p d a t i n g The R e p e t i t i v e S t r u c t u r e The c o n t i n u o u s u p d a t i n g a l g o r i t h m p r o v i d e s a r o b u s t u p d a t i n g p r o c e s s f o r networks based on low l e v e l d a t a . The r e p e t i t i v e s t r u c t u r e i s e s s e n t i a l l y c o m p a t i b l e w i t h the a l g o r i t h m as i t i s a l s o b u i l t from low l e v e l i n f o r m a t i o n (premise of h i g h l e v e l i n p u t ) . Some c l a r i f i c a t i o n however, must be g i v e n t o update d a t a which does not f u l l y agree w i t h the r e p e t i t i v e a c t i v i t y d e f i n i t i o n . T h i s s e c t i o n d i s c u s s e s the f l e x i b i l i t y of the update p r o c e s s r e q u i r e d t o model the r e p e t i t i v e s t r u c t u r e and p r o v i d e s a p r o c e d u r e t o meet i t s needs. I f a crew i s p r e s e n t l y w o r k i n g on two f l o o r s , the model must r e c o g n i z e the crew i s b a l a n c i n g i t s time between m u l t i p l e ongoing l o c a t i o n s . T h i s was o f t e n found t o happen on s i t e ; a crew would be i n the p r o c e s s of f i n i s h i n g one l o c a t i o n and s t a r t i n g a n o t h e r . A l s o , the model must a d j u s t t o update d a t a which does not f o l l o w i t s d e s i g n a t e d f l o o r sequence. T h i s s i t u a t i o n o c c u r r e d f r e q u e n t l y due t o l a c k of space or d r y i n g t i m e s r e q u i r i n g the s u b c o n t r a c t o r t o work around c e r t a i n l o c a t i o n s . The above cases a r e a d d r e s s e d i n the r e p e t i t i v e b u i l d i n g p r o c e s s by means of the update b l o c k o f the r e p e t i t i v e a c t i v i t y f l o w c h a r t ( F i g u r e 2.21). The p r o c e s s i s as f o l l o w s . G iven the s e q u e n t i a l i n p u t f i l e ( F i g u r e 2.17), a l l completed l o c a t i o n s a r e removed s i n c e they do not have t o be 94 s c h e d u l e d . Ongoing l o c a t i o n s a r e then p r o c e s s e d through the update b l o c k . The sc h e d u l e d l o c a t i o n s a r e f u r t h e r added t o the s t r u c t u r e as d e s c r i b e d i n S e c t i o n 2.5.4. The update b l o c k of the f l o w c h a r t has been expanded i n F i g u r e 3.11 and i t s p r o c e d u r e o u t l i n e d below i n the f o l l o w i n g s e c t i o n . 3.7.1 The Update B l o c k Each ongoing l o c a t i o n must be checked t o see how much l o n g e r ( i f a t a l l ) i t r e q u i r e s the shared r e s o u r c e s . T h i s i s a c h i e v e d by f i n d i n g i t s A c t u a l S t a r t Date and then a d d i n g the time i t r e q u i r e s the shared r e s o u r c e s minus the time i t has a l r e a d y used them (Sb = ASD + SS - {TNOW - ASD}). I f the v a l u e of Sb i s l e s s than TNOW, the crew no l o n g e r r e q u i r e s the sh a r e d r e s o u r c e s and Sb i s g i v e n the v a l u e of TNOW and p l a c e d i n P o o l B to show t h a t the r e s o u r c e s a r e a v a i l a b l e i m m e d i a t e l y . I f the v a l u e of Sb i s g r e a t e r than TNOW, the crew s t i l l r e q u i r e s the shared r e s o u r c e s and i t s v a l u e i s p l a c e d d i r e c t l y i n t o P o o l B t o denote the day the shared r e s o u r c e s w i l l be a v a i l a b l e n e x t . The re m a i n i n g d u r a t i o n i s added, a l o n g w i t h any FS l i n k , t o the update date t o e s t a b l i s h when t h e crew of the ongoing l o c a t i o n w i l l be a v a i l a b l e (Sa = TNOW + REMDUR +FS). The Sa v a l u e i s then p l a c e d i n P o o l A. The rem a i n i n g d u r a t i o n of the ongoing a c t i v i t y must be r e c o r d e d i n f i l e SEQ i f i t i s t o be i n c l u d e d i n the s c h e d u l e . As such, the ongoing l o c a t i o n i s g i v e n a s t a r t date e q u a l t o the update date ( S i = TNOW). The f i n i s h of the re m a i n i n g d u r a t i o n i s a l s o p l a c e d i n f i l e SEQ and i s c a l c u l a t e d 95 S = l * of O n g o i n g l o c a t i o n s = C * of S h a r e d R e s o u r c e s = X * o f c r e w s w o r k i n g = N N O C a l c u l a t e w h e n c r e w i s f i n i s h e d w i t h s h a r e d r e s o u r c e s . S b = A S D + l S S - ( T N O W - A S D ) ] C a l c u l a t e w h e n c r e w i s a v a i l a b l e n e x t . S a + T N O W + R E M D U R + F S P r o c e e d t o m o d e l r e m a i n i n g p a r t o f o n g o i n g l o c a t i o n , s t a r t i n g a t T N O W . S i = T N O W C a l c u l a t e f i n i s h by a p p l y i n g t h e R e m a i n i n g D u r a t i o n . F i = T N O W + R E M D U R R e p e a t f o r e a c h O n g o i n g l o c a t i o n S = S * 1 S > C ? Y E S G i v e X b a t c h e s of S h a r e d R e s o u r c e s t o t h e X l a t e s t c r e w s t o u s e t h e m . G i v e * t o X l a t e s t S b ' s D e n o t e a v a i l a b l e c r e w s by t a k i n g t h e N l a t e s t l o c a t i o n s to be s t a r t e d . G i v e * t o N l a t e s t A S D ' s T To Repetitive Activity Flowchart. APPL YSb TO POOL A APPLY Sa TO POOL B APPLY Si=I TO OUTPUT APPLY Fi TO OUTPUT M U . . . , . H . 4ppi y * TO POOL B •»«....u,|||i.. APPL Y * TO POOL A F i g u r e 3.11 The R e p e t i t i v e A c t i v i t y Update F l o w c h a r t 96 by adding the r e m a i n i n g d u r a t i o n t o the update date ( F i = TNOW + REMDUR). T h i s p r o c e s s i s r e p e a t e d f o r a l l ongoing l o c a t i o n s . Once a l l of the ongoing l o c a t i o n s have been c a l c u l a t e d , i t i s time t o d e s i g n a t e the p o s i t i o n s of a l l r e s o u r c e s ( i . e . crews and shared r e s o u r c e s ) . T h i s can be d i f f i c u l t i f t h e r e are crews w i t h m u l t i p l e ongoing l o c a t i o n s s i n c e the p o s i t i o n i n g of crews and r e s o u r c e s i s not c l e a r from the update d a t a g i v e n . T h i s d a t a can be asked of the u s e r but would r e q u i r e a s u b s t a n t i a l i n c r e a s e t o the update data i n p u t s m o n i t o r e d i n S e c t i o n 2.5.1. The a l g o r i t h m t h e r e f o r e s e t s a c o n v e n t i o n which a l l o w s the p r o c e s s t o be performed a u t o m a t i c a l l y . 3.7.2 Update C o n v e n t i o n f o r the R e p e t i t i v e A c t i v i t y As a l l ongoing l o c a t i o n s are a l l o w e d t o c o n t i n u e t h e i r p r o g r e s s ( S e c t i o n 3.6.10), the placement of r e s o u r c e s does not a f f e c t t h e i r t i m i n g . A l s o , any d u r a t i o n a l l o w a n c e f o r h a n d l i n g m u l t i p l e l o c a t i o n s per crew w i l l be r e f l e c t e d i n the " r e m a i n i n g d u r a t i o n " i n p u t by the u s e r . T h e r e f o r e , the importance of l o c a t i n g the r e s o u r c e s of a r e p e t i t i v e a c t i v i t y l i e s i n the a v a i l a b i l i t y of crews and shared r e s o u r c e s f o r the l o c a t i o n s y e t t o be performed.•Based on t h i s p r e m i s e , X b a t c h e s of shared r e s o u r c e s a r e l o c a t e d on the X ongoing l o c a t i o n s which f i n i s h l a s t . L i k e w i s e , the Y crews a r e l o c a t e d on the Y ongoing l o c a t i o n s which were s t a r t e d l a s t . 97 As shared r e s o u r c e s must be used by a l l l o c a t i o n s , the above assumption w i l l produce the c o r r e c t p lacement, as the l a t e s t ongoing l o c a t i o n s o b v i o u s l y r e q u i r e the s h a r e d r e s o u r c e s l a s t ( p r o v i d e d they a r e performed t o c o m p l e t i o n once shared r e s o u r c e s are a v a i l a b l e ) . The crew assumption a l s o r e f l e c t s c o r r e c t r e s o u r c e placement f o r most s i t u a t i o n s ( i . e . a crew p r o c e e d s t o i t s next l o c a t i o n even though the c u r r e n t l o c a t i o n i s not q u i t e f i n i s h e d ; a crew s k i p s one l o c a t i o n because of t e c h n i c a l problems and proceeds t o the n e x t ) . However, i t i s p o s s i b l e t o produce m i s l e a d i n g r e s u l t s i f a crew s i m u l t a n e o u s l y s t a r t s two new l o c a t i o n s . The a u t h o r b e l i e v e s t h a t such a s i t u a t i o n does not r e f l e c t the c o n t i n u i t y by which the a c t i v i t y i s m o d e l l e d (crews p r o g r e s s i n g a l o c a t i o n a t a time) and would r e q u i r e an a c t i v i t y r e v i e w by the u s e r . Note, the crew a s s u m p t i o n does a l l o w t h i s s i t u a t i o n t o be p r o c e s s e d and hence m a i n t a i n a s c h e d u l e , a l b e i t based on c o n t i n u i t y which might not e x i s t . An example of an updated r e p e t i t i v e a c t i v i t y i s shown i n F i g u r e 3.12. Note t h a t a l l l i n k s (FS, SS) are i n c l u d e d , a l o n g w i t h t h e new l i n k s of ongoing l o c a t i o n s t o TNOW. 98 L E V E L 1 C O M P L E T E D . L E V E L 2 R E M A I N I N G D U R A T I O N = 1 D A Y . L E V E L 4 R E M A I N I N G D U R A T I O N = 2 D A Y S . L E V E L 5 N O T S T A R T E D . L E V E L 6 N O T S T A R T E D . F i g u r e 3.12 Example of an Updated R e p e t i t i v e A c t i v i t y  3.8 The Computer Model The p r o t o t y p e system i s implementated on an IBM P e r s o n a l Computer (PC) a t The U n i v e r s i t y of B r i t i s h C o lumbia. I t i n c l u d e s i n t e g r a t i o n of the c o n t i n u o u s u p d a t i n g a l g o r i t h m w i t h the extended d e f i n i t i o n of Laramee's r e p e t i t i v e a c t i v i t y s t r u c t u r e as d e s c r i b e d i n Chapter I I . Work i s c u r r e n t l y underway t o i n c o r p o r a t e a l l a s p e c t s of t h i s c h a p t e r . T h i s e n t a i l s a d o p t i n g t h e a u t h o r ' s d e f i n i t i o n of the r e p e t i t i v e a c t i v i t y p r o c e s s t o 99 ta k e f u l l advantage of the r e s o u r c e l e v e l l i n g f l e x i b i l i t y as d e s c r i b e d i n S e c t i o n 3.7. 3.9 C o n c l u s i o n A d e f i n i t i v e u p d a t i n g p r o c e s s was e v o l v e d through the a n a l y s i s of two s i t e s t u d i e s . The g o a l was t o g i v e the user an ongoing . p i c t u r e of the s c h e d u l e , backed w i t h s u f f i c i e n t i n f o r m a t i o n t o perform the everyday d e c i s i o n s i n h e r e n t on a c o n s t r u c t i o n s i t e . The p r o c e s s u t i l i z e d the s t r u c t u r e of a CMIS t o i n t e g r a t e u p d a t i n g i n t o the company s t r a t e g y . A c o n t i n u o u s u p d a t i n g a l g o r i t h m was d e s i g n e d t o remove unnecessary user involvement and ensure c o n t i n u o u s m o n i t o r i n g of the p r o j e c t . D u r i n g the many c o n t i n u o u s u p d a t i n g phases performed i t proved t o be r e a l i s t i c and r o b u s t . The a l g o r i t h m t h u s p r o v i d e d a r e s p o n s i v e u p d a t i n g p r o c e s s which enhances the h e u r i s t i c n a t u r e by which the c o n s t r u c t i o n i n d u s t r y a p p l i e s d e c i s i o n a n a l y s i s and c o n t r o l . 100 CHAPTER IV FURTHER ISSUES AND CONCLUSION 4.1 I n t r o d u c t i o n The purpose of t h i s c h a p t e r i s t o summarize the ty p e s of c o n t i n u i t y r e q u i r e m e n t s encountered i n p r a c t i c e which can be su p p o r t e d by a d e f i n i t i o n of the r e p e t i t i v e - a c t i v i t y and t h e r f o r e which s h o u l d be a l l o w e d f o r i n the d e s i g n of a system. Problems of i n t e g r a t i n g a c o m p u t e r i z e d system i n t o the i n d u s t r y are a l s o d i s c u s s e d . The uses of the system i n r e s p e c t t o u p d a t i n g and da t a s t o r a g e a re examined w i t h a l o o k a t p o s s i b l e e x t e n s i o n s i n t o the f i e l d of " e x p e r t " or "smart" systems. Recommendations f o r f u t u r e work a r e then g i v e n . The c h a p t e r ends w i t h the c o n c l u s i o n t o the t h e s i s . 4.2 The G e n e r a l i t y of R e p e t i t i v e Work Throughout the t h e s i s , the r e p e t i t i v e a c t i v i t y was d e s c r i b e d i n terms of a h i g h - r i s e p r o j e c t . Such c o n s t r u c t i o n l e n d s i t s e l f t o c o n t i n u i t y as each f l o o r can o n l y be b u i l t i f the f l o o r below i s completed. The p r o c e s s s t a r t s w i t h t h e s u p e r s t r u c t u r e and then l e a d s n a t u r a l l y t o the b u i l d i n g s e r v i c e s and i n t e r i o r f i n i s h i n g . The r e p e t i t i v e a c t i v i t y was found t o be p r e s e n t a t s u c c e s s i v e l o c a t i o n s and p r o g r e s s up the s t r u c t u r e . 101 Thus the a c t i v i t y was t y p i c a l l y d e s c r i b e d as r e g u l a r and o m n i d i r e c t i o n a l . Such a d e s c r i p t i o n d e f i n e s many l i n e a r p r o j e c t s such as roadways and p i p e l i n e s . The ALRT p r o j e c t was mentioned i n Chapter I I . I t was n o t e d f o r i t s n o n - s e q u e n t i a l l o c a t i o n p a t t e r n which responded t o the d i f f e r e n t d e s i g n s e c t i o n s of the m o n o r a i l columns. Thus, the r e p e t i t i v e a c t i v i t y d i d not f o l l o w the l i n e a r p r o g r e s s i o n of the m o n o r a i l but s k i p p e d a l o n g i t s l e n g t h a t p a r t i c u l a r l o c a t i o n s . T h i s type of r e p e t i t i v e n a t u r e was c l a s s i f i e d as. n o n - r e g u l a r y e t o m n i d i r e c t i o n a l . Such a c t i v i t i e s are o f t e n seen on l i n e a r p r o j e c t s which d i s p l a y two or more c h a r a c t e r i s t i c s t h a t d i c t a t e the c o n s t r u c t i o n methodology of the l o c a t i o n s . For example, a highway t h a t has v a r y i n g c u t and f i l l s e c t i o n s , or a t r a n s m i s s i o n l i n e whose tower d e s i g n s change due t o the l o a d c h a r a c t e r i s t i c s i t s u p p o r t s . C e r t a i n p r o j e c t s which d i s p l a y l i n e a r work are o f t e n c o n s t r u c t e d from b o t h ends s i m u l t a n e o u s l y and p r o g r e s s t o the m i d d l e where the j o b i s c o mpleted. The purpose i s to speed up the p r o j e c t by i n c r e a s i n g the manpower y e t a v o i d i n g the problems of c o n g e s t i o n . T h i s method i s o f t e n used f o r b r i d g e spans p a r t i c u l a r l y of the s u s p e n s i o n d e s i g n where the l a r g e c a n t i l e v e r e d s e c t i o n s cause g r e a t s t r e s s e s d u r i n g the c o n s t r u c t i o n phase. I t i s a l s o found on t u n n e l l i n g p r o j e c t s where s i t e c o n g e s t i o n i s a s i g n i f i c a n t c o n s t r a i n t . Such p r o j e c t s a r e found t o e x h i b i t both r e g u l a r and n o n - r e g u l a r r e p e t i t i o n . Each end u s u a l l y has i t s own r e s o u r c e s and thus i s l i k e l y 102 m o d e l l e d as an independent r e p e t i t i v e a c t i v i t y . C e r t a i n p r o j e c t s show a r e p e t i t i v e n a t u r e even though the l o c a t i o n s a r e not s e t out i n a l i n e a r p a t t e r n . For example an apartment b u i l d i n g composed of one and two bedroom u n i t s . There a r e o b v i o u s l y many r e p e t i t i v e a c t i v i t i e s t o be performed per u n i t . T h e r e f o r e , the m o d e l l i n g of the p r o j e c t c o u l d be planned as l i n e a r by d e f i n i n g l o c a t i o n s i n the orde r i n which they are t o be completed. As the o r d e r of the p r o j e c t i s not based on i t s p h y s i c a l l a y o u t , such c a s e s - o f t e n show- a g r e a t e r v a r i e t y of r e p e t i t i v e a c t i v i t i e s t o o p t i m i z e shared r e s o u r c e s . Other s i m i l a r p r o j e c t s e n c o u n t e r e d d u r i n g t h i s t h e s i s i n c l u d e s u b d i v i s i o n s , commercial b u i l d i n g s and s p o r t s t a d i u m s . R e p e t i t i v e p r o j e c t s a r e t o be found i n many a s p e c t s of c o n s t r u c t i o n . C o n t i n u i t y and rhythm are o f t e n s i g n i f i c a n t f a c t o r s by which a p r o j e c t i s p l a n n e d . I t i s i m p o r t a n t t o a l l o w the s c h e d u l e r t o model t h e s e q u a l i t i e s i f c o m p u t e r i z e d s c h e d u l i n g i s t o be a u s e f u l management t o o l . 4.3 Computer Implementation and the C o n s t r u c t i o n I n d u s t r y Changes, w h i l e p r e v a l e n t on the s i t e , a r e not easy t o i n i t i a t e i n the management s t r u c t u r e . Most management comprises of p e r s o n n e l who have worked t h e i r way up th r o u g h the r a n k s . Such p e o p l e have a keen u n d e r s t a n d i n g of the i n d u s t r y , y e t o f t e n l a c k any t h e o r y by which t o manage i t . 1 03 T h i s p r o f i l e of c o n s t r u c t i o n management was made c l e a r d u r i n g the i n i t i a t i o n of the C r i t i c a l P a t h Method i n the T960's. I t s c o m p l e x i t y and numerous c a l c u l a t i o n s h i n d e r e d i t s a c c e p t a n c e . W h i l e i t s has been s l o w l y adopted, few c o n s t r u c t i o n p e r s o n n e l u n d e r s t a n d the t h e o r y by which i t works, t h u s l e a v i n g i t open f o r abuse. U n d e r s t a n d i n g i s o n l y shown a t i t s lowest l e v e l of o u t p u t s , such as the bar c h a r t and c r i t i c a l p a t h . Both the u p d a t i n g and r e p e t i t i v e a c t i v i t y d e f i n i t i o n s d e s c r i b e d i n t h i s t h e s i s , were b u i l t w i t h t h i s i n mind. The i n p u t s were kept as s i m p l e as p o s s i b l e and a l l assumptions m i n i m i z e d t o p r e v e n t abuse due t o a m i s u n d e r s t a n d i n g of the t h e o r y . The r e p e t i t i v e a c t i v i t y r e q u i r e s i n p u t s which the user i n t u i t i v e l y c o n s i d e r s when f o r m u l a t i n g the j o b : p r o d u c t i o n r a t e , l o c a t i o n s and r e s o u r c e s . The a l g o r i t h m p e r f o r m s a matching of i n p u t s t o ensure a l l crews a r e c o n s i s t a n t l y w o r k i ng when r e s o u r c e s a r e a v a i l a b l e . The user c o u l d p e r f o r m t h i s f u n c t i o n manually i f time p e r m i t t e d . The u p d a t i n g a l g o r i t h m r e q u i r e s no more i n p u t s than those a l r e a d y used by c o n s t r u c t i o n p e r s o n n e l on t h e i r d a i l y p r o gess r e p o r t s . The a l g o r i t h m bypasses l i n k s which were found not t o e x i s t and adds new l i n k s t o ongoing a c t i v i t i e s t o m a i n t a i n automatic network i n t e g r i t y . A l l l i n k s chosen a r e based on the most r e c e n t d a t a a v a i l a b l e . 1 04 The a u t h o r c o n t r i b u t e s the q u i c k acceptance of the above d e f i n i t i o n s t o t h e i r s i m p l e , y e t r e a l i s t i c n a t u r e . C o n s t r u c t i o n p e r s o n n e l f e l t c o m f o r t a b l e c o n v e r s i n g i n the format of the a l g o r i t h m s . The s t r a i g h t f o r w a r d p r i n c i p l e s of the p r o c e s s promoted c o n s i d e r a b l e f a i t h i n the system. 4.3.1 User I n t e r f a c e A c t u a l f i e l d t r i a l s gave the author an i n s i g h t t o i n i t i a t i n g computers i n c o n s t r u c t i o n . A most i m p o r t a n t premise i s t h a t of keeping the user-computer i n t e r a c t i o n s i m p l e . T h i s i s p a r t i a l l y c o n t r o l l e d by the s i m p l i c i t y of the i n p u t s r e q u i r e d of the u s e r , but a l s o i m p o r t a n t i s i t s p r e s e n t a t i o n on the s c r e e n . T h i s i s known as the user i n t e r f a c e . Important t o a s u c c e s s f u l user i n t e r f a c e a r e c o n c i s e commands s u p p o r t e d where p o s s i b l e by g r a p h i c s . The language of c o n v e r s a t i o n s h o u l d be n a t u r a l t o the u s e r . I t s h o u l d i n c l u d e c o n c e p t s which a r e a l r e a d y known or can be e a s i l y l e a r n t ; acronyms s h o u l d be e s t a b l i s h e d terms of the c o n s t r u c t i o n i n d u s t r y . User i n t e r f a c e d e s i g n p r i n c i p l e s have been o u t l i n e d by F o l e y and VanDam (Reference 10), some of which can be a p p l i e d t o the c o n s t r u c t i o n i n d u s t r y . These i n c l u d e p r o v i d i n g feedback t o u s e r i n p u t s ( e choeing) t o promote c o n f i d e n c e i n the system and 1 05 p r o v i s i o n f o r a c o r r e c t i o n mechanism t o pre v e n t i n h i b i t i o n of the system's use. C o n s i s t e n c y i n the d i s p l a y of i n f o r m a t i o n i s ve r y i m p o r t a n t t o g a i n a f e e l i n g of f a m i l i a r i t y from the user as i s the m i n i m i z a t i o n of u s e r r e c a l l needed from s c r e e n t o s c r e e n . An i m p o r t a n t f a c t o r n o t e d by the a u t h o r and mentioned by F o l e y and VanDam i s the need f o r "human-factors f i n e - t u n i n g " or f i e l d t r i a l s of the system. 4.4 Computers and Data S t o r a g e An i s s u e of u p d a t i n g which has not been a d d r e s s e d i s t h a t of the s t o r a g e r e q u i r e m e n t s of o l d s c h e d u l e s . Once a r e v i s e d s c h e d u l e i s a c c e p t e d the o l d s c h e d u l e i s no l o n g e r used. However, i t does c o n t a i n d a t a s t i l l of use t o the c o n t r a c t o r . I t can be used i n l i t i g a t i o n , management r e p o r t s and as f u t u r e r e f e r e n c e on new p r o j e c t s . In l i t i g a t i o n i t i s o f t e n n e c e s s a r y t o p r o v i d e the c o u r t w i t h a h i s t o r i c a l account of the p r o j e c t . Lee ( R e f e r e n c e 17) s t a t e s the importance of both the "As-planned" and " A s - b u i l t " s c h e d u l e s f o r time impact a n a l y s i s t o s e t t l e c l a i m s . Such f o r e n s i c s c h e d u l i n g u t i l i z i n g network methodology i s w e l l a c c e p t e d i n l i t i g a t i o n , p a r t i c u l a r l y when the s c h e d u l e s a r e p r e p a r e d so t h a t a d i r e c t comparison can be made between them. F i s k ( R e f e r e n c e 9) o u t l i n e s the c o n s i d e r a b l e importance of p r o j e c t documentation and emphasizes the need f o r t i m e l y e n t r i e s i n t o d i a r i e s and l o g s so t h a t i n f o r m a t i o n l o s s i s m i n i m i z e d . 106 W e l l documented p r o j e c t s g r e a t l y s t r e n g t h e n a_ case i n c o u r t . Management r e p o r t s are o f t e n e x t r a c t e d from the s c h e d u l e t o show p a r t i c u l a r a s p e c t s of the p r o j e c t . These o f t e n denote the problem a r e a s or d e l i v e r a c o n c i s e o v e r v i e w of the p r o j e c t . Such r e p o r t s are a l s o u s e f u l f o r s u p p o r t i n n e g o t i a t i o n s and the a r b i t r a t i o n p r o c e s s e s t h a t can a r i s e . They co v e r a wide range of c o l l e c t e d d a t a and can v a r y e x t e n s i v e l y i n t h e i r d e t a i l of time a n a l y s e s . H i s t o r i c a l d a t a bases are u s e f u l f o r e s t i m a t i n g f u t u r e j o b s . While such d a t a i s t r a d i t i o n a l l y g a i n e d from an e s t i m a t o r ' s e x p e r i e n c e , m a i n t a i n i n g i t on a d a t a base a l l o w s data r e t e n t i o n when c o n s t r u c t i o n p e r s o n n e l change and p r o v i d e s a q u i c k and complete r e f e r e n c e t o o l . Data s t o r a g e r e q u i r e m e n t s depend on the demands of the system. I t i s e x p e c t e d t h a t most c o n t r a c t o r s would w i s h t o r e t a i n enough d a t a f o r l i t i g a t i o n and minimal r e p o r t i n g . T h i s would r e q u i r e the s t o r a g e of a l l documentation and a l l r e v i s e d s c h e d u l e s . P e r i o d i c updated s c h e d u l e s s h o u l d a l s o be s t o r e d t o show o v e r a l l s i t e p r o g r e s s and t o h i g h l i g h t s p e c i f i c a r e a s of i n t e r e s t . Any f u r t h e r d a t a base f o r purposes of e s t i m a t i n g or d e t a i l e d r e p o r t i n g w i l l depend on management and t h e i r d e s i r e d knowledge base. 1 07 4.5 E x p e r t Systems A p r o m i s i n g emerging h y b r i d of management systems i s the e x p e r t system. I t e s s e n t i a l l y p e r f orms a l l f u n c t i o n s of the CMIS, p l u s has the a b i l i t y t o a n a l y z e and o f f e r s u g g e s t i o n s on problem area s which a r i s e based on knowledge g a i n e d from c o n s t r u c t i o n e x p e r t s (Reference 13). Such a system c o u l d e s t a b l i s h i t s e l f i n the c o n s t r u c t i o n i n d u s t r y where i t c o u l d perhaps be used t o balance o f f the l a c k of t h e o r y of c o n s t r u c t i o n p e r s o n n e l who use CPM base' systems. Fenves (Re f e r e n c e 8) r e c o g n i z e d the use of e x p e r t systems f o r m o n i t o r i n g the c o n s t r u c t i o n p r o c e s s . S i t u a t i o n s which i t c o u l d h e l p i n c l u d e h i g h consumption of f l o a t , p o s s i b l e procurement d e l a y s , and update l o g i c which does not conform t o s c h e d u l e d l o g i c . Such s i t u a t i o n s a r e easy t o mo n i t o r i n the t h e o r e t i c a l sense but can elud e the u s e r . I t c o u l d thus p r o v i d e f o r e s i g h t of p o t e n t i a l problems and p o i n t out a r e a s where the model does not f i t w e l l w i t h the a c t u a l p r o j e c t d a t a . The u p d a t i n g a l g o r i t h m d e s c r i b e d i n t h i s t h e s i s c o u l d be s a i d t o f i t some of the c h a r a c t e r i s t i c s of an e x p e r t system as i t d i c t a t e s the v a l i d i t y of l o g i c l i n k s based on a s e t of r u l e s d e v e l o p e d from the c o n s t r u c t i o n i n d u s t r y . I t thus p r o v i d e s the user w i t h an update s t a t u s and p o i n t s out a r e a s which must be r e v i e w e d i n o r d e r t o g i v e an an a c c e p t a b l e outcome. Such i n f e r e n c e a l l o w s the user t o b e n e f i t from u p d a t i n g procedures used by e x p e r i e n c e d p e r s o n n e l and i n v o k e s o r g a n i z a t i o n and 108 f o r m u l a t i o n of the thought p r o c e s s used. An e x p e r t system demands c r i t e r i a by which i t can a s s e s s the c u r r e n t s i t u a t i o n . A p a r t from the t h e o r e t i c a l p o i n t s o u t l i n e d above, i t c o u l d be p r o v i d e d w i t h u s e r s p e c i f i e d c r i t e r i a . T h i s would i n c l u d e a g i v e n v a r i a n c e i n p r o d u c t i o n r a t e s of a c t i v i t i e s , s p e c i f i e d a l l o w a b l e s l i p p a g e of a m i l e s t o n e , f o r e c a s t i n g of a c t i v i t y c o m p l e t i o n based on e a r l e r p r o j e c t s or e x t r a p o l a t e d v a l u e s . The e x p e r t system o f f e r s many o p p o r t u n i t i e s t o the c o n s t r u c t i o n i n d u s t r y . I t s assessments c o u l d o f f e r a r o b u s t a n a l y s i s and be f i n e - t u n e d by the i n d i v i d u a l u s e r . C o n s t r u c t i o n p e r s o n n e l c o u l d b e n e f i t from e x p e r t a n a l y s i s of the many h e u r i s t i c s i t u a t i o n s t h a t a r i s e . I t i s a t o o l which would f o r c e r e s e a r c h e r s t o t a k e a c l o s e r l o o k a t how a c o n s t r u c t i o n p r o j e c t i s a c t u a l l y run and g r e a t l y a i d i n making computers more c o m p a t i b l e w i t h the c o n s t r u c t i o n i n d u s t r y . 4.6 Recommendations f o r F u t u r e Work The g e n e r a l d e f i n i t i o n of the r e p e t i t i v e a c t i v i t y i s not y e t implemented i n t o the p r o t o t y p e system a t the U n i v e r s i t y of B r i t i s h C o lumbia. There i s a need t o t e s t t h i s d e f i n i t i o n t o ensure i t can model the m a j o r i t y of work p a t t e r n s found i n c o n s t r u c t i o n . I t s i n t e g r a t i o n w i t h the c o n t i n u o u s u p d a t i n g p r o c e s s must a l s o be completed. T h i s s h o u l d not prove t o be 1 09 d i f f i c u l t as the u p d a t i n g has a l r e a d y been shown t o work w e l l w i t h the extended v e r s i o n of Laramee's r e p e t i t i v e s t r u c t u r e . The above work i s e x p e c t e d t o be implemented i n t o the system i n the near f u t u r e . A l t h o u g h t h i s w i l l complete the f o c u s of t h e s i s , the a u t h o r s u g g e s t s some new a r e a s of i n t e r e s t by which the u s e a b i l i t y of c o m p u t e r i z e d s c h e d u l i n g may be enhanced. A most imp o r t a n t a r e a y e t t o be c a p t u r e d i n c o n s t r u c t i o n management i s t h a t of u s e r i n t e r f a c e . Of p a r t i c u l a r importance i s the e x p l o i t a t i o n of g r a p h i c s t o p o r t r a y i n p u t s and the p r o j e c t as a whole. T h i s i s a d i f f i c u l t t a s k f o r time c e n t r e s tend t o be v e r y l a r g e and d i f f i c u l t t o d i s p l a y on a s c r e e n . R e p e t i t i v e a c t i v i t i e s can b e n e f i t g r e a t l y by a g r a p h i c d i s p l a y of the s t r u c t u r e b e f o r e i t i s i n c o r p o r a t e d i n t o the network. The user can thus q u i c k l y f o l l o w each crew's movement a l o n g the p r o j e c t and p i c k out any problems which may be be a p p a r e n t . G r a p h i c d i s p l a y s of s e c t i o n s of the network would a l s o h e l p d i s t i n g u i s h r e l a t i o n s h i p s between s p e c i f i c groups of a c t i v i t i e s . T h i s a r e a r e q u i r e s c o n s i d e r a b l e work t o c a p t u r e the format by which t h e • c o n s t r u c t i o n i n d u s t r y may best g a i n . I t i s e x p e c t e d t h a t some problems of g r a p h i c p r e s e n t a t i o n may be s o l v e d w i t h the f u t u r e advancements i n computer g r a p h i c s . A d a t a s t o r a g e system t o save a l l p r o g r e s s d a t a c o u l d be d e v e l o p e d and s t o r e d i n a s t a n d a r d base f o r the c o n s t r u c t i o n i n d u s t r y t o t a k e f u l l advantage of the update a l g o r i t h m . Computer t e c h n o l o g y i s q u i c k l y a l l o w i n g l a r g e b l o c k s of d a t a t o 110 be s t o r e d a t m i n i m a l c o s t . Such knowledge w i l l p r o v i d e the e x p e r i e n c e of f i n i s h e d p r o j e c t s t o be a p p l i e d t o f u t u r e work t h r o u g h w e l l s u p p o r t e d c o s t i n g and s c h e d u l i n g d a t a and t h rough the enhancement of the d e c i s i o n making p r o c e s s . D e v e l o p i n g an e x p e r t system based on p r e v a l e n t problem a r e a s i n c o n s t r u c t i o n i s an a r e a t h a t needs immediate a t t e n t i o n . I t s p o t e n t i a l t o f o c u s the u s e r ' s c o n c e n t r a t i o n and c o n f i d e n c e on t h e computer system s u p p o r t s i t s development. Work must be f o c u s e d on the problem are a s of s c h e d u l i n g . E x p e r t s must be found t o a p p l y t h e i r knowledge t o c r e a t i n g problem s o l v i n g t e c h n i q u e s . Such methodology i s d i f f i c u l t t o g e n e r a t e w i t h c u r r e n t computer hardware. F u t u r e r e a l i z a t i o n of p a r a l l e l p r o c e s s i n g w i l l g r e a t l y a i d i n i t s i m p l e m e n t a t i o n . 4.7 C o n c l u s i o n The g o a l of t h i s t h e s i s was t o promote the u s e a b i l i t y of c o m p u t e r i z e d s c h e d u l i n g systems i n the c o n s t r u c t i o n i n d u s t r y . T h i s g o a l has been met t h rough the development of two a l g o r i t h m s . The d e f i n i t i o n of the g e n e r a l r e p e t i t i v e s t r u c t u r e p r o v i d e s c o n s t r u c t i o n p e r s o n n e l w i t h a t o o l by which t o model the p r o c e s s of r e p e t i t i o n found i n many c o n s t r u c t i o n s i t e s . T h i s a l l o w s the user t o s c h e d u l e the work f l o w p a t t e r n s by which the rhythm of a p r o j e c t i s c o n t r o l l e d . 111 The d e f i n i t i o n of the c o n t i n u o u s u p d a t i n g a l g o r i t h m p r o v i d e s the user w i t h a sc h e d u l e c a p a b l e of m o n i t o r i n g the d a i l y p r o g r e s s of the c o n s t r u c t i o n s i t e . I t demands no more i n p u t s than r e q u i r e d i n a t y p i c a l d a i l y p r o g r e s s r e p o r t . The a l g o r i t h m t h u s a l l o w s the user to respond t o everyday changes i n the c o n s t r u c t i o n s i t e and implement e f f e c t i v e c o n t r o l . Both a l g o r i t h m s have been based on a s i m p l e h e u r i s t i c approach t o promote t h e i r i n t e g r a t i o n i n t o the c o n s t r u c t i o n i n d u s t r y . Care was taken t o m a i n t a i n a user f r i e n d l y system through e x t e n s i v e f i e l d o b s e r v a t i o n s and t e s t i n g t o u n d e r s t a n d the b a s i c s by which p r o j e c t s a r e f o r m u l a t e d and c o n t r o l l e d . The s i t e s t u d i e s show the a l g o r i t h m s t o be both r e a l i s t i c and r o b u s t . They have been found t o f i t w e l l w i t h c o n s t r u c t i o n management p h i l o s o p h y . The t h e s i s t h u s c r e a t e s two u s e a b l e t o o l s which advance the u s e a b i l i t y of c o m p u t e r i z e d s c h e d u l i n g i n the c o n s t r u c t i o n i n d u s t r y . 1 12 BIBLIOGRAPHY 1. Anderson, H., F j o s n e , A., and S o l b e r g , 0., "A Network Model f o r Resource A l l o c a t i o n and Time Space S c h e d u l i n g S p e c i a l l y C o n s t r u c t e d f o r R e p e t i t i v e P r o c e s s e s i n the B u i l d i n g I n d u s t r y " , A p p l i c a t i o n s of C r i t i c a l Techniques , 1978, pp. 7 t o 23. 2. B a r r i e , D.S. and P a u l s o n , B.C. J r . , " P r o f e s s i o n a l C o n s t r u c t i o n Management", M c G r a w - H i l l Book Company, New Y o rk, Second E d i t i o n , 1984. 3. 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