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UBC Theses and Dissertations

An experimental investigation of a precast concrete connection Saxena, Rajiv Prakash 1983

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EXPERIMENTAL INVESTIGATION OF A PRECAST CONCRETE CONNECTION by; RAJIV PRAKASH SAXENA M.E.(CIVIL) COLLEGE OF ENGINEERING, PUNE-INDIA, 1979 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in THE FACULTY OF GRADUATE STUDIES CIVIL ENGINEERING DEPARTMENT We accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA SEPTEMBER 1983 © Rajiv Prakash Saxena, 1983 .1 In presenting t h i s thesis in p a r t i a l fulfilment of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t freely available for reference and, study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his or her representatives. It i s understood that copying or publication of th i s thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of CIVIL ENGINEERING The University of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date: 24 September,1983 i i f o r o n i w i t h l o v e and a f f e c t i o n ABSTRACT Tests on discrete connections for precast concrete panel buildings have shown that i t is very d i f f i c u l t to design a duc t i l e embedded connection. Typical connections use studs or reinforcing bars embedded in the edge of the panel and connected to the connection in an adjacent panel with a weld plate or ribbed bar. This is welded either to an exposed length of the embedded steel or to an angle or plate which i s welded to the embedded s t e e l . Under earthquake loading the crushing of concrete around the embedment usually leads to premature loss of strength and s t i f f n e s s of the connection before any s i g n i f i c a n t d u c t i l i t y can occur. If the connections of the precast concrete buildings cannot develop adequate d u c t i l i t y either the whole structure must be designed to remain e l a s t i c during an earthquake, or the connections must be stronger than other elements in the structure which can develop the necessary d u c t i l i t y . In practice both of these alternatives may be d i f f i c u l t to achieve. An al t e r n a t i v e approach is to use a y i e l d i n g connector between embedments in adjacent precast panels, in place of a r i g i d weld plate or bar. One way to do t h i s i s to use a mild steel tube with a longitudinal s l i t to permit shear d i s t o r t i o n under earthquake loading. This d e t a i l w i l l also accomodate r e l a t i v e i v movement betwen panels due to shrinkage and temperature changes. Twenty five s p l i t pipe connection specimens, made from four di f f e r e n t types of pipe, were tested under c y c l i c shear loading. Results obtained for the strength, s t i f f n e s s and d u c t i l i t y of these connections are presented and discussed. A simple formula for c a l c u l a t i n g the shear strength of these connections is proposed. V TABLE OF CONTENT DEDICATION ABSTRACT TABLE OF CONTENTS L I S T OF TABLES L I S T OF FIGURES L I S T OF PHOTOGRAPHS ACKNOWLEDGEMENT CHAPTER 1 INTRODUCTION CHAPTER 2 REVIEW OF CONNECTION DESIGNS FOR PRECAST CONCRETE 7 2.1 E n e r g y D i s s i p a t i o n M e c h a n i s m 7 2.2 T y p e s o f C o n n e c t i o n s 8 2.2.1 C o n n e c t i o n s U s i n g C a s t - I n - P l a c e C o n c r e t e o r M o r t a r 8 2.2.2 M e c h a n i c a l C o n n e c t i o n s 9 2.2.3 C o n n e c t i o n s U s i n g W e l d i n g o f S t e e l P a r t s 9 2.3 L o c a t i o n o f C o n n e c t i o n s 10 2.3.1 C o n n e c t i o n Between F l o o r P a n e l s 10 2.3.2 H o r i z o n t a l C o n n e c t i o n B e t w e e n W a l l P a n e l s 12 2.3.3 C o n n e c t i o n Between W a l l P a n e l s And Page No. i i i i i v i x x x i i i xv 1 F o u n d a t i o n s 13 2.3.4 V e r t i c a l C o n n e c t i o n s Between W a l l P a n e l s 13 2.3.4.1 Embedded C o n n e c t i o n s W i t h R i g i d W e l d P l a t e s 16 2.3.4.2 L i m i t e d S l i p B o l t e d C o n n e c t i o n s 16 2.3.4.3 Embedded R e b a r C o n n e c t i o n 19 2.3.4.4 Embedded C o n n e c t i o n s W i t h D u c t i l e W e l d P l a t e 19 CHAPTER 3 LABORATORY TEST DETAILS 22 3.1 A s s u m p t i o n s Made F o r The T e s t s 22 3.2 T e s t S p e c i m e n 26 3.3 T e s t R i g 27 3.4 L o a d i n g Yoke 27 3.5 T e s t R i g M o d i f i c a t i o n s 30 3.6 D i s p l a c e m e n t M e a s u r e m e n t 32 3.7 D a t a A c q u i s i t i o n S y s t e m 36 3.7.1 Use o f The S y s t e m 37 3.7.1.1 O p e r a t i o n o f NEFF 38 3.7.1.2 O p e r a t i o n o f PDP-11/10 38 3.8 L o a d i n g P r o c e d u r e 39 3.9 L a b o r a t o r y T e s t i n g 42 CHAPTER 4 GEOMETRY OF TEST RIG 47 4.1 P a n e l B e h a v i o u r U n d er S h e a r L o a d 47 v i i 4.2 Test Rig Geometry 54 CHAPTER 5 EXPERIMENTAL RESULTS 59 5.1 Connection Results 59 5.2 Pipe Group 1 63 5.2.1 Connection 1-1 63 5.2.2 Connection 1-2 66 5.2.3 Connection Notched 1-3 70 5.2.4 Connection 1-4 74 5.2.5 Connection Notched 1-5 74 5.2.6 Connection 1-6 77 5.2.7 Connection Notched 1-7 77 5.2.8 Connection 1-8 84 5.2.9 Connection 1-9 84 5.2.10 Connection Notched 1-10 88 5.3 Pipe Group 2 88 5.3.1 Connection 2-1 88 5.3.2 Connection Notched 2-2 90 5.3.3 Connection 2-3 94 5.3.4 Connection Notched 2-4 94 5.3.5 Connection 2-5 97 5.3.6 Connection Notched 2-6 97 5.4 Pipe Group 3 101 5.4.1 Connection 3-1 101 5.4.2 Connection 3-2 103 5.4.3 Connection Notched 3-3 106 v i i i 5.4.4 C o n n e c t i o n Notched 3-4 108 5.4.5 C o n n e c t i o n 3-5 111 5.4.6 C o n n e c t i o n Notched 3-6 111 5.4.7 C o n n e c t i o n 3-7 114 5.4.8 C o n n e c t i o n Notched 3-8 118 5.5 P i p e Group 4 120 5.5.1 C o n n e c t i o n 4-1 120 5.6 Test R e s u l t s 120 5.6.1 S t r e n g t h of P i p e 120 5.6.2 S t i f f n e s s C a l c u l a t i o n s 121 5.6.3 D e f l e c t i o n R e s u l t s 122 5.6.4 D u c t i l i t y C a l c u l a t i o n s 122 CHAPTER 6 DISCUSSION, CONCLUSIONS AND FUTURE SCOPE 132 6.1 D i s c u s s i o n and C o n c l u s i o n s 132 6.1.1 S t r e n g t h of P i p e 132 6.1.2 S t i f f n e s s of P i p e 134 6.1.3 D e f l e c t i o n of P i p e 135 6.1.4 D u c t i l i t y of P i p e 136 6.1.5 Recommendations f o r D e t a i l C o n n e c t i o n Design 137 6.2 F u t u r e Scope 138 REFERENCES 145 i x L I S T OF TABLES T a b l e No. Page No. 3.1 P i p e S p e c i f i c a t i o n s 43 3.2 R e c o r d o f T e s t Done i n L a b o r a t o r y 44 4.1 I n t e r a c t i o n C u r v e s F o r P a n e l B e h a v i o u r 51 5.1 Summary o f L a b o r a t o r y R e s u l t s 60 5.2 E l a s t i c S t i f f n e s s e s o f C o n n e c t i o n s 124 5.3 E l a s t i c D e f l e c t i o n s a n d P l a s t i c D e f l e c t i o n s 126 5.4 D u c t i l i t y o f N o t c h e d a n d U n n o t c h e d P i p e s 128 5.5 D e f l e c t i o n s f o r D i f f e r e n t D u c t i l i t y 130 X LIST OF FIGURES Figure No. P a g e N o > 1.1 Typical Precast Concrete Panel Building 3 2.1 Types of Joints in Large Panel Buildings 11 2.2 Connection of Precast Elements With Loops 1 1 2.3 Modes of Deformations of Structures for Various Conditions 14 2.4 Typical Stud Headed Connection Showing Two common Stud Configurations 17 2.5 Typical Details of Limited S l i p (LSB) Joints 18 2.6 Embedded Rebar Connection Detail 20 2.7 S p l i t Pipe Connection Detail 21 3.1 Notched Pipe 23 3.2 Face Plate and Test Model 24 3.3 Test Set Up Rig 25 3.4 Loading Yoke - Top Cross Beam And Side Arm D e t a i l 29 3.5 Loading Yoke ~ Bottom Cross Beam Details 31 3.6 LVDT Mounting 35 3. ,7 Loading Sequence 41 3. .8 S p l i t Pipe Connection 46 4. 1 Rotation of Panels Under Shear Load 48 4. 2 Interaction Graph for Panel Behaviour 52 4. 3 Interaction Graph for Panel Behaviour 53 4. 4 Behaviour of Test Set Up Under Shear Load 55 4. 5 Interaction Graph for Test Set Up Geometry 56 4. 6 Superimposed Interaction Curves (For Test Set Up Dimensions) 58 5. 1 (a) Normal S l i t Of Pipe 64 5. 1 (b) S l i t After Few Cycles 64 5. 2 Development Of Crack For Unnotched Pipe 65 5. 3 Hysteresis Loop For Connection Number 1 -1 68 5. 4 Hysteresis Loop For Connection Number 1 -2 69 5. 5 Crack Propagation In Notched Pipe 72 5. 6 Hysteresis Loop For Connection Number 1 -3 73 5. 7 Hysteresis Loop For Connection Number 1 -4 76 5. 8 Hysteresis Loop For Connection Number 1 -5 78 5. 9 Hysteresis Loop For Connection Number 1 -6 80 5. 1 0 Crack Pattern For Nottched Pipe 81 5. 1 1 Hysteresis Loop For Connection Number 1 -7 83 5. 1 2 Hysteresis Loop For Connection Number !• -8 85 x i i 5.13 D e v e l o p m e n t Of C r a c k F o r U n n o t c h e d P i p e s A f t e r T e s t R i g M o d i f i c a t i o n s 86 5.14 H y s t e r e s i s L o o p F o r C o n n e c t i o n Number 1-9 87 5.15 H y s t e r e s i s L o o p F o r C o n n e c t i o n Number 1-10 89 5.16 H y s t e r e s i s L o o p F o r C o n n e c t i o n Number 2-1 92 5.17 H y s t e r e s i s L o o p F o r C o n n e c t i o n Number 2-2 93 5.18 H y s t e r e s i s L o o p F o r C o n n e c t i o n Number 2-3 95 5.19 H y s t e r e s i s L o o p F o r C o n n e c t i o n Number 2-4 98 5.20 H y s t e r e s i s L o o p F o r C o n n e c t i o n Number 2-5 100 5.21 H y s t e r e s i s L o o p F o r C o n n e c t i o n Number 2-6 102 5.22 F a i l u r e Of U n n o t c h e d P i p e U n d er S h e a r L o a d 104 5.23 H y s t e r e s i s L o o p F o r C o n n e c t i o n Number 3-1 105 5.24 H y s t e r e s i s L o o p F o r C o n n e c t i o n Number 3-2 107 5.25 H y s t e r e s i s L o o p F o r C o n n e c t i o n Number 3-3 109 5.26 H y s t e r e s i s L o o p F o r C o n n e c t i o n Number 3-4 110 5.27 H y s t e r e s i s L o o p F o r C o n n e c t i o n Number 3-5 113 5.28 H y s t e r e s i s L o o p F o r C o n n e c t i o n Number 3-6 115 5.29 H y s t e r e s i s L o o p F o r C o n n e c t i o n Number 3-7 116 5.30 H y s t e r e s i s L o o p F o r C o n n e c t i o n Number 3-8 119 6.1 S h e a r S t r e n g t h Of S p l i t P i p e 140 6.2 V a r i a t i o n o f P i p e S t r e n g t h - 141 6.3 V a r i a t i o n o f P i p e S t r e n g t h 142 6.4 V a r i a t i o n o f Maximum D e f l e c t i o n 143 6.5 V a r i a t i o n o f D u c t i l i t y 144 x i i i LIST OF PHOTOGRAPHS Photo No. Page No. 3.1 S l i t Pipe 28 3.2 Test Rig Before Modifications 28 3.3 Test Rig After Modifications 33 3.4 Test Rig After Modifications 33 3.5 Test Rig After Modifications 34 3.6 Displacement Measurement 34 3.7 Hydraulic Jack 40 3.8 Load C e l l 40 5.1 Crack Pattern for Connection 1-1 67 5.2 Distortion of Connection 1-2 67 5.3 Cracks for Connection 1-3 71 5.4 Cracks for Connection 1-3 71 5.5 Cracks For Connection 1-4 75 5.6 Crack Pattern for Connection 1-4 75 5.7 Failure of Connection 1-6 79 5.8 Failure of Connection 1-6 79 5.9 Failure of Connection 1-7 82 5.10 Failure of Connection 2-1 91 5.11 Distortion of Connection 2-4 96 5.12 Dist o r t i o n of Connection 2-5 99 5.13 Failure of connection 3-1 112 5.14 Distortion of Connection 3-5 112 x i v 5.15 F a i l u r e of C o n n e c t i o n 3-7 117 5.16 F a i l u r e of C o n n e c t i o n 3-7 117 XV ACKNOWLEDGEMENT Author wishes to thank Dr. Richard A. Spencer for his advice and guidance. Thanks are due to Dr. D. L. Anderson, Dr. N.D. Nathan, and Dr. S. Mindess for their help and to a l l technicians for the help during the experimental work. (RAJIV P. SAXENA) 1 CHAPTER 1  INTRODUCTION Panelized or precast construction i s used for multi-storey apartment buildings a l l over the world. Interest in the design and construction of large panel structures has increased in North America in recent years. Panelized building systems are constructed of large precast concrete panels used as both v e r t i c a l and horizontal structural components. Increasing prefabrication in the building industry appears to be inevitable, and the tendency to depart from conventional types of reinforced concrete construction i s ever increasing. The construction industry can r e a l i z e greater speed of erection as well as reduced labour costs with precast construction. For example, erecting the exterior walls „ of a 100,000 sq.ft.(9300 sq.m.) precast building w i l l require about one week's time, whereas using conventional construction methods i t might require as long as a month to erect the same walls. An average of 40 panels can be erected in one day 2 1. There i s steadily increasing use of precast concrete 2 i n b u i l d i n g s b o t h a s p r e c a s t c l a d d i n g f o r p r e c a s t o r c o n v e n t i o n a l f r a m e s , and a s l o a d b e a r i n g u n i t s i n l a r g e p a n e l b o x - t y p e b u i l d i n g s i n w h i c h t h e c o n v e n t i o n a l f r a m e i s o m i t t e d a l t o g e t h e r a nd t h e l o a d s a r e c a r r i e d by t h e p r e c a s t u n i t s t h e m s e l v e s . P r e c a s t c o n c r e t e p a n e l c o n s t r u c t i o n h a s f o u n d i t s w i d e s t u se i n r e s i d e n t i a l c o n s t r u c t i o n where p a n e l s may s e r v e a s m u l t i - f u n c t i o n a l b u i l d i n g e l e m e n t s . P r e c a s t u n i t s i n a s i n g l e s t o r e y l a r g e p a n e l b u i l d i n g a r e shown i n f i g u r e 1.1. T h e s e t y p e s o f s t r u c t u r e s have been c o n s t r u c t e d i n e a r t h q u a k e z o n e s i n C a n a d a , t h e U n i t e d S t a t e s , t h e S o v i e t U n i o n , R u m a n i a , C u b a , J a p a n , I n d i a a n d a r e g r a d u a l l y s p r e a d i n g t o o t h e r p l a c e s ' 1 0 , 1 5 ' . R e s e a r c h r e p o r t s h a v e d e s c r i b e d t e s t s on f u l l s c a l e s t r u c t u r e s , u n d e r l a t e r a l l o a d s o r u n d e r b l a s t l o a d i n g s ' 2 , 3 , 1 2 , 1 3 , 1 6 , 1 7 , 1 9 , 2 2 , 2 7 , 3 6 ' . T h e s e t e s t s were done on d w e l l i n g s t r u c t u r e s i n t e n d e d f o r mass p r o d u c t i o n , a n d t h e r e s u l t s c a n o n l y be r e g a r d e d a s q u a l i t a t i v e w i t h r e s p e c t t o p r e c a s t p a n e l s t r u c t u r e s i n g e n e r a l . I n most c o n c r e t e b u i l i n g s , i t i s u n e c o n o m i c a l t o a t t e m p t t o r e s i s t t h e f o r c e s g e n e r a t e d d u r i n g l a r g e e a r t h q u a k e s w i t h i n t h e l i m i t s o f t h e e l a s t i c r e s p o n s e o f t h e s t r u c t u r e . D u r i n g r a r e g r o u n d a c c e l e r a t i o n s o f l a r g e i n t e n s i t y , i n e r t i a f o r c e s e q u a l t o t h e l a t e r a l l o a d c a p a c i t y o f t h e s t r u c t u r e may be i n d u c e d a n d h e n c e Typical precast concrete panel building. 4 y i e l d i n g and consequent p l a s t i c deformations may occur at some or a l l c r i t i c a l areas within the structure. To prevent loss of l i f e in a severe earthquake, i t is necessary to ensure that the post-elastic deformations in various parts of the structure can occur without leading to complete structural collapse. The design philosophy i s : a) E l a s t i c response and minimum damage for moderate earthquake; b) i n e l a s t i c behaviour, without s t r u c t u r a l collapse, in severe earthquakes. F l e x i b l e structures w i l l develop r e l a t i v e l y large deflections and as a consequence r e l a t i v e l y small i n e r t i a forces; conversely more r i g i d structures w i l l develop large i n e r t i a forces but smaller d e f l e c t i o n s 1 . The current building codes require structures to exhibit s u f f i c i e n t d u c t i l i t y to allow them to deform i n e l a s t i c a l l y without collapse. The maximum t o t a l deformation i s often assumed to be 3 to 4 times the maximum e l a s t i c deformations, and may be more for f l e x i b l e s t r u c t u r e s 2 6 . A d u c t i l e connection between two precast panels can help to ensure a safe structure. Earthquake damage in concrete panel buildings is almost always along join t s with l i t t l e damage in the panels, and some of the energy generated during an earthquake can be dissipated through 5 the j o i n t s . This can be achieved by designing connections which can deform i n e l a s t i c a l l y without fracture, even under several cycles of large displacement reversals, and s t i l l maintain their ultimate capacity. It i s l i k e l y that in the near future panelized construction w i l l tend to be preferred to cast-in-place construction for multi-storey shear walls. Panelized walls a t t r a c t less i n e r t i a forces. Quoting Despeyroux "prefabricated walls are therefore to be considered better than monolithic walls as far as earthquakes are concerned" 8 . Present information on precast connections is primarily for monotonic loading with some limited information from fatigue and c y c l i c tests' 6, 2•, 2 8 , 2 9 , 3 1 , 3 f l , 3 5 ' . Matrix analysis using the displacement method has been used to analyse the linear and non-linear behaviour of precast buildings and j o i n t s ' 2 3 , 3 7 ' . The s t a t i c s t a b i l i t y of hinge-connected structures has also been investigated using matrix f o r m u l a t i o n 3 2 . Failure modes for joints and walls have been studied by comparing the stresses in the wall due to v e r t i c a l and horizontal loading and the joint s t r e n g t h 3 3 . This investigation deals with the analysis, design and development of a du c t i l e connection d e t a i l for use 6 w i t h p r e c a s t p a n e l s . A s p l i t p i p e i s u s e d t o l i m i t f o r c e i n t h e c o n c r e t e p a n e l s and h e n c e d i s s i p a t e e n e r g y . V a r i o u s s p l i t p i p e s were t e s t e d u n d e r c y c l i c l o a d i n g and t h e r e s u l t s a r e s u m m a r i z e d f o r d i f f e r e n t p i p e d i a m e t e r s and t h i c k n e s s e s . 7 C H A P T E R 2 R E V I E W OF C O N N E C T I O N D E S I G N S FOR P R E C A S T C O N C R E T E A r e v i e w o f e n e r g y d i s s i p a t i o n m e c h a n i s m s i s p r e s e n t e d . Some p o s s i b l e l o c a t i o n s f o r p r e c a s t c o n n e c t i o n s a r e d i s c u s s e d a l o n g w i t h t h e i r m e r i t s a n d d e m e r i t s . A v e r t i c a l j o i n t i s o n e g o o d p o s s i b l e l o c a t i o n f o r e n e r g y d i s s i p a t i o n i n p r e c a s t c o n c r e t e s t r u c t u r e s s u b j e c t e d t o e a r t h q u a k e s . A n u m b e r o f c o n n e c t i o n s a r e c o n s i d e r e d a n d c o m p a r e d t o t h e p r o p o s e d c o n n e c t i o n . 2.1 E N E R G Y D I S S I P A T I O N M E C H A N I S M T h e u s e o f p a n e l i z e d p r e c a s t c o n c r e t e b u i l d i n g s i n m a n y o f t h e e a r t h q u a k e p r o n e r e g i o n s o f t h e w o r l d r a i s e s m a n y q u e s t i o n s i n e a r t h q u a k e r e s i s t a n t d e s i g n . I n m o s t c a s e s e a r t h q u a k e d a m a g e i n l a r g e p a n e l s t r u c t u r e s o c c u r s a l o n g t h e c o n n e c t i o n l i n e s . T h e d e s i g n o f g o o d c o n n e c t i o n d e t a i l s i n v o l v e s t h e b a l a n c i n g o f e c o n o m i c s a n d e a s e o f c o n s t r u c t i o n o n t h e o n e h a n d w i t h t h e n e e d f o r c o n t i n u i t y a n d r e a s o n a b l e d u c t i l i t y o n t h e o t h e r . C o n n e c t i o n s a r e c o n s i d e r e d t o b e t h e w e a k l i n k s i n t h e p a n e l b u i l d i n g s u n d e r s e v e r e g r o u n d m o t i o n s , a n d m a y b e p r i m a r i l y r e s p o n s i b l e f o r i n t r o d u c i n g n o n - l i n e a r b e h a v i o u r i n t h e o v e r a l l b u i l d i n g s y s t e m . O n e d e s i g n a p r o a c h i s t o 8 assume t h a t t h e p r e c a s t p a n e l s w i l l r e m a i n e l a s t i c u n d e r e a r t h q u a k e l o a d i n g . Thus c o n n e c t i o n s a r e t h e p r i n c i p a l l o c a t i o n s where e n e r g y c a n be d i s s i p a t e d e f f e c t i v e l y . I f t h e p a n e l s r a t h e r t h a n t h e c o n n e c t i o n s a r e d e s i g n e d t o i n t r o d u c e n o n - l i n e a r i t y i n a b u i l d i n g s y s t e m , t h e r e i s a g r e a t e r l i k e l i h o o d o f a p r o g r e s s i v e c o l l a p s e o f t h e s t r u c t u r e . Thus d u c t i l e c o n n e c t i o n s s u i t a b l y p l a c e d b e t w e e n p a n e l s c a n i n t r o d u c e d u c t i l i t y a n d i m p r o v e t h e s e i s m i c r e s i s t a n c e o f p r e c a s t p a n e l b u i l d i n g s . 2.2 TYPES OF CONNECTIONS • T h e r e a r e numerous c o n n e c t i o n methods b u t c o n n e c t i o n s c a n be b r o a d l y c l a s s i f i e d i n t o f o l l o w i n g c a t e g o r i e s 9 . 2.2.1 CONNECTIONS USING CAST-IN-PLACE CONCRETE OR  MORTAR Th e s e a r e a l s o known a s wet c o n n e c t i o n s . F i l l e r c o n c r e t e o r m o r t a r , u s u a l l y o f r e l a t i v e l y l o w c o m p r e s s i v e s t r e n g t h , ( a b o u t 3.0 K s i . ) i s p l a c e d i n t h e c o n n e c t i o n a f t e r t h e p a n e l s a r e p l a c e d i n p o s i t i o n . The b e h a v i o u r o f t h e s e c o n n e c t i o n s w i l l d e p e n d upon f i v e b a s i c p a r a m e t e r s : a) C o n c r e t e s t r e n g t h - o f b o t h t h e p a n e l s a n d t h e i n - s i t u c o n n e c t i o n c o n c r e t e ; b) s u r f a c e p r e p a r a t i o n o f p a n e l s - p a n e l e d g e s 9 may be l e f t plain or they can be grooved; c) connection reinforcement - thi s includes type of steel and location of steel within the connection. This reinforcing steel i s often used lo n g i t u d i n a l l y within the connection as well as across the connection; d) force transverse to connection - thi s force can be from gravity loads or post-tensioning; e) shear connectors - placed in the face of joint against shear forces at the j o i n t . 2.2.2 MECHANICAL CONNECTIONS These methods make use of bolts and inserts and are a type of dry-connection. High tension bolts and post tensioning may be used in these type of connections. 2.2.3 CONNECTIONS USING WELDING OF STEEL PARTS These are methods in which steel embeddments (usually plates or bars) that are well anchored to the members to be connected, are provided at locations which permit members to be connected to one another by welding. This is c a l l e d a dry-connection. The joints exhibit s a t i s f a c t o r y strength immediately after completion of welding which shortens the construction period. 10 2.3 LOCATION OF CONNECTIONS I n p r e c a s t p a n e l c o n s t r u c t i o n , t h e r e a r e b a s i c a l l y f i v e l o c a t i o n s i n w h i c h t h e c o n n e c t i o n s c a n d i s s i p a t e e n e r g y d u r i n g an e a r t h q u a k e ( f i g u r e 2 . 1 ) . a) c o n n e c t i o n s b e t w e e n f l o o r p a n e l s ; b) h o r i z o n t a l c o n n e c t i o n s b e t w e e n w a l l p a n e l s ; c ) c o n n e c t i o n s b e t w e e n f l o o r a n d w a l l p a n e l s ; d) v e r t i c a l c o n n e c t i o n s b e t w e e n w a l l p a n e l s ; e) c o n n e c t i o n s b e t w e e n w a l l p a n e l s a n d f o u n d a t i o n s . 2.3.1 CONNECTION BETWEEN FLOOR PANELS The f o r c e s w i t h i n t h e f l o o r d i a p h r a g m s a r e r e l a t i v e l y s m a l l h e n c e t h e r e i s l i t t l e p r o b a b i l i t y o f s l i p p a g e o r e n e r g y d i s s i p a t i o n i n t h e f l o o r c o n n e c t i o n s . A l s o f l o o r s y s t e m s o f t e n h a v e s i g n i f i c a n t l y r e d u c e d i n -p l a n e s t i f f n e s s when c o m p a r e d t o c a s t - i n - p l a c e s y s t e m s . T h i s r e d u c e d s t i f f n e s s a n d t h e d i f f i c u l t y i n a c h i e v i n g a d e q u a t e t e n s i l e c o n t i n u i t y p o s e s p r o b l e m s i n t h e a n a l y s i s a n d d e s i g n 2 0 . F r a n z h a s s u g g e s t e d c o n n e c t i o n s o f p r e c a s t e l e m e n t s w i t h m i l d s t e e l r e i n f o r c i n g s t e e l f o r a d j a c e n t f l o o r p a n e l s 1 " ( f i g u r e 2 . 2 ) . Shemie h a s a l s o p r o p o s e d c o n n e c t i o n s . b e t w e e n f l o o r p a n e l s u s i n g b o l t s 3 0 . 11 F i g . 2.1 Types Of J o i n t s In Large Panel B u i l d i n g s loop type 1 loop type 2 F i g . 2.2 Connection Of P r e c a s t Elements With Loops 1 2 2.3.2 HORIZONTAL CONNECTION BETWEEN WALL PANELS The h o r i z o n t a l c o n n e c t i o n b e t ween w a l l p a n e l s i s n o t a d e s i r a b l e l o c a t i o n f o r e n e r g y d i s s i p a t i o n , b e c a u s e t h e n e c e s s a r y s l i d i n g movements w i l l o c c u r o n l y a t t h e most h i g h l y l o a d e d p l a n e s , a n d t h e d e f o r m a t i o n s w i l l be p e r m a n e n t a s t h e r e a r e no c o r r e c t i v e e l a s t i c f o r c e s a c t i n g t o s t r a i g h t e n t h e b u i l d i n g ( f i g u r e 2 . 3 a ) . I n a s e v e r e e a r t h q u a k e t h i s may l e a v e t h e s t r u c t u r e u n s e r v i c e a b l e f o l l o w i n g t h e e a r t h q u a k e . A p u r e r o c k i n g t y p e m o t i o n , when t h e v e r t i c a l c o n n e c t i o n s l i p s , t h e o v e r a l l b u i l d i n g i . e . , o p e n i n g a n d c l o s i n g o f c o n n e c t i o n ( f i g u r e 2.3b) i n a t y p i c a l h o r i z o n t a l c o n n e c t o n , e v e n i f p o s t - t e n s i o n e d , d o e s n o t c a u s e e f f i c i e n t e n e r g y d i s s i p a t i o n ( 5 , 1 8 > . T h i s o p e n i n g a n d c l o s i n g o f h o r i z o n t a l c o n n e c t i o n , a s s o c i a t e d w i t h r o c k i n g , l e a d s t o a p r o g r e s s i v e s o f t e n i n g o f t h e s t r u c t u r e w i t h i n c r e a s e d e x c i t a t i o n l e v e l . M u e l l e r a n d B e c k e r h a v e s u g g e s t e d a s t r o n g h o r i z o n t a l a n d a weak v e r t i c a l c o n n e c t i o n a s e i s m i c d e s i g n p h i l o s o p h y " . R o c k i n g c o u p l e d w i t h l o c a l a n d g l o b a l s h e a r s l i p l e a d s t o s i g n i f i c a n t f o r c e c o n c e n t r a t i o n s i n t h e c o r n e r s o f p a n e l s . I t i s f e l t t h a t s u c h f o r c e c o n c e n t r a t i o n s , u n l e s s s p e c i f i c a l l y d e s i g n e d f o r , w i l l l e a d t o a p r o g r e s s i v e d e t e r i o r a t i o n o f t h e p a n e l c o r n e r s i n a s e v e r e e a r t h q u a k e . Shemie h a s p r o p o s e d a s l i p b o l t c o n n e c t i o n f o r a h o r i z o n t a l c o n n e c t i o n 2 9 . Dowri'ck h a s a l s o p r o p o s e d some 1 3 d r y c o n n e c t i o n d e t a i l s b e t ween p r e c a s t f l o o r s a n d w a l l s 1 1 . 2.3.3 CONNECTION BETWEEN WALL PANELS AND FOUNDATIONS The c o n n e c t i o n s b e t w e e n t h e w a l l p a n e l s and f o u n d a t i o n d e p e n d s on t h e u n d e r l y i n g s o i l s t r a t a c h a r a c t e r i s t i c s and t h e t o t a l h e i g h t o f t h e b u i l d i n g . B a se i s o l a t e r s m i g h t be more u s e f u l t h a n a c o n n e c t i o n . The p r i n c i p l e l i e s i n d e c o u p l i n g t h e s t r u c t u r e f r o m t h e g r o u n d d u r i n g an e a r t h q u a k e , o f any m a g n i t u d e , and i n c h a n g i n g i t s o s c i l l a t i o n c h a r a c t e r i s t i c s s o t h a t t h e a c c e l e r a t i o n s w h i c h t h e g r o u n d t r a n s m i t t o t h e s t r u c t u r e becomes m i n i m a l . 2.3.4 VERTICAL CONNECTIONS BETWEEN WALL PANELS V e r t i c a l c o n n e c t i o n s , o f s u f f i c i e n t d u c t i l i t y , b e t w e en w a l l p a n e l s a p p e a r t o o f f e r t h e most p r o m i s i n g s o u r c e o f e n e r g y d i s s i p a t i o n . These c o n n e c t i o n s d i s s i p a t e n e a r l y 8 5 - 9 0 % o f t h e t o t a l e n e r g y g e n e r a t e d d u r i n g an e a r t h q u a k e . U n l i k e h o r i z o n t a l c o n n e c t i o n s , t h e v e r t i c a l c o n n e c t i o n s , a f t e r s l i p p a g e t o d i s s i p a t e e n e r g y , w i l l r e t u r n t o t h e i r o r i g i n a l a l i g n m e n t u n d e r e l a s t i c a c t i o n , w i t h l i t t l e o r no p e r m a n e n t d e f o r m a t i o n , i f t h e w a l l p a n e l s and t h e h o r i z o n t a l c o n n e c t i o n s r e m a i n undamaged ( f i g u r e 2 . 3 c ) . A l s o when -i t 1 i i i t i I i 1 1 1 a) Horizontal Shear S l i p b) Rocking i j f 1 c) V e r t i c a l Shear S l i p F i g . 2.3 Modes Of Deformations Of Structures For Various Conditions 1 5 t h e v e r t i c a l c o n n e c t i o n s l i p s , t h e o v e r a l l b u i l d i n g r i g i d i t y i s r e d u c e d , t h e r e b y l e n g t h e n i n g t h e e f f e c t i v e p e r i o d o f t h e b u i l d i n g , w h i c h may be b e n e f e c i a l t o t h e s t r u c t u r e f o r i t s s t a b i l i t y a f t e r t h e e a r t h q u a k e h a s p a s s e d . E v e n i n e x t r e m e l o a d i n g c a s e s , t h e f a i l u r e o f a few c o n n e c t i o n s i s n o t l i k e l y t o t h r e a t e n t h e o v e r a l l s t a b i l i t y o f t h e s t r u c t u r e a s t h e s e a r e n o t t h e g r a v i t y l o a d c a r r y i n g c o n n e c t i o n s . A l s o a c a r e f u l d e s i g n o f v e r t i c a l c o n n e c t i o n s w i l l a v o i d a p r o g r e s s i v e f a i l u r e o f t h e s t r u c t u r e . P o s s i b l e l o c a t i o n s f o r e f f i c i e n t v e r t i c a l c o n n e c t i o n s d e s i g n e d t o d i s s i p a t e e n e r g y c o u l d b e 2 5 . a) C o n t i n u o u s c o n n e c t i o n s i n t h e end w a l l p a n e l s ; b) c o n n e c t i o n s b e t w e e n c o r r i d o r l i n t e l s ; c ) c o n n e c t i o n s a t r i g h t a n g l e j o i n t s b e t w e e n p a n e l s i . e . I o r T s e c t i o n s a r o u n d e l e v a t o r s h a f t s a n d s t a i r c a s e s e t c . R e s e a r c h e r s have s u g g e s t e d a number o f j o i n t s f o r v e r t i c a l c o n n e c t i o n s . T h e s e i n c l u d e : a) Embedded c o n n e c t i o n s w i t h r i g i d w e l d p l a t e ; b) l i m i t e d s l i p b o l t e d c o n n e c t i o n s ; c ) embedded r e b a r c o n n e c t i o n s ; d) embedded c o n n e c t i o n s w i t h d u c t i l e w e l d p l a t e c o n n e c t i o n s . 16 2.3.4.1 EMBEDDED CONNECTIONS WITH RIGID WELD PLATES C y c l i c t e s t s f o r some c o n n e c t i o n s o f t h i s t y p e w h i c h u se h e a d e d s t u d s were r e p o r t e d by S p e n c e r a nd N e i l l e 3 1 . A t y p i c a l c o n n e c t i o n i s shown i n f i g u r e 2.4. T h e s e c o n n e c t i o n s , i f p r o p e r l y d e s i g n e d , d e t a i l e d a n d f a b r i c a t e d f o r a p r e c a s t p a n e l b u i l d i n g , a p p e a r t o be s u i t a b l e f o r use i n e a r t h q u a k e r e s i s t a n t b u i l d i n g s d e s i g n e d a s b o x - t y p e s y s t e m s i n t e n d e d t o r e m a i n e l a s t i c d u r i n g an e a r t h q u a k e . As r e p o r t e d t h e s e c o n n e c t i o n s have v e r y l i m i t e d d u c t i l i t y . 2.3.4.2 LI M I T E D S L I P BOLTED CONNECTIONS The D r e s c o n - C o n c o r d i a s y s t e m 7 u s e s b o l t e d c o n n e c t i o n s f o r h o r i z o n t a l w a l l - t o - w a l l and s l a b - t o - s l a b c o n n e c t i o n s b u t n o t f o r t h e v e r t i c a l c o n n e c t i o n s . However t h i s s y s t e m was e x t e n d e d t o a p r o p o s e d w a l l c o n n e c t i o n 2 4 . S l o t s a r e made i n t h e c o n n e c t i n g p l a t e b e t w e e n p r e c a s t w a l l p a n e l s . T e s t s showed t h a t w i t h s l o t t e d h o l e s t h e f r i c t i o n a l movement c o u l d g i v e t h e d e s i r e d e n e r g y d i s s i p a t i o n w i t h o u t c a u s i n g i n e l a s t i c y i e l d i n g o f t h e m a t e r i a l s . The c o n n e c t i o n i s d e s i g n e d n o t t o s l i p u n d e r s e r v i c e l o a d s , b u t i s e x p e c t e d t o s l i p d u r i n g s e v e r e s e i s m i c e x c i t a t i o n s . A t y p i c a l c o n n e c t i o n i s shown i n f i g u r e 2.5. 17 F i g . 2.4 Typical Stud Headed Connection Showing Two Common Stud Configurations 18 weld offer erection 0 CD plate red 14— insert — joint ELEVATION 0 o 0 CD CONNECTING PLATE lectina L L , t anchors ponel INSERT connecting plate bolts (ASTM A325) insert SECTION nuts welded to insert Fig. 2.5(a) .wall panels 1 Jrl • connecting angles bolts -connecting angles -insert -wall panel (ASTM A325) insert wall panel SECTION SECTION F i g . 2.5(b) a) S i m p l e W a l l - T o - W a l l J o i n t b) C o r n e r W a l l - T o - W a l l J o i n t F i g . 2.5 T y p i c a l D e t a i l s Of L i m i t e d S l i p (LSB) J o i n t s 1 9 2.3.4.3 EMBEDDED REBAR CONNECTION S t e e l r e i n f o r c i n g b a r s a r e u s e d f o r c o n n e c t i o n . I n e a c h edge t h e r e i s a s m a l l a n g l e a n c h o r e d w i t h two r e b a r s a t 45°. The s h e a r s t r e n g t h o f t h e c o n n e c t i o n i s c a l c u l a t e d f r o m f o r c e c o m p o n e n t s i n t h e a n c h o r b a r s . Enough d e v e l o p m e n t l e n g t h i s p r o v i d e d t o d e v e l o p t h e bond b e t w e e n c o n c r e t e a n d s t e e l . A t y p i c a l r e b a r c o n n e c t i o n i s shown i n f i g u r e 2.6. D u c t i l i t y e n s u r e d by t h e s e c o n n e c t i o n s i s n o t a v a i l a b l e i n t h e l i t e r a t u r e . 2.3.4.4 EMBEDDED CONNECTIONS WITH DUCTILE WELD PLATE A d i f f e r e n t a p p r o a c h f r o m t h e c o n v e n t i o n a l r i g i d w e l d p l a t e o r b a r i s p r o p o s e d . A s t e e l p i p e w i t h a l o n g i t u d i n a l s l i t i s w e l d e d b e t w e e n embeddments i n a d j a c e n t p r e c a s t p a n e l s . T h i s d e t a i l w i l l a l s o be a b l e t o a c c o m o d a t e r e l a t i v e movement b e t w e e n p a n e l s due t o s h r i n k a g e a n d t e m p e r a t u r e c h a n g e . A s p l i t p i p e c o n n e c t o r i s shown i n f i g u r e 2.7. Under d y n a m i c l o a d s t h e p a n e l s s h o u l d r e m a i n l a r g e l y undamaged, b e c a u s e t h e c o n n e c t i o n l i m i t s t h e f o r c e s t h a t c a n d e v e l o p i n t h e s t r u c t u r e - . 20 F i g . 2.6 Embedded Rebar Connecti D e t a i l 21 F i g . 2.7 S p l i t Pipe Connection D e t a i l 22 CHAPTER 3 LABORATORY TEST DETAILS Pipe lengths of 6.0", 8.0" and 10.0" with a longitudinal s l i t (photo 3.1) were studied under reversed c y c l i c shear loading. Pipe diameters were chosen between 1.0" to 2.25" with wall thicknesses of 0.125" to 0.25". The test assembly fabricated was able to simulate a quasi-s t a t i c shear loading. Shear load and shear displacements were measured for these tests. Assumptions, test model, testing r i g , loading yoke, displacement measurement, data a c q u i s i t i o n procedure, loading procedure etc. are also discussed. A t y p i c a l s p l i t pipe test model i s shown in figure 3.1. A connection using t h i s s p l i t pipe i s shown in figure 3.8. 3.1 ASSUMPTIONS MADE FOR THE TESTS An isolated s p l i t pipe connector i s tested as shown in figure 3.3. It i s assumed that when these s p l i t pipe connections are used in a precast wall panel they w i l l behave in more or less the same fashion. Dynamic laboratory testing of the complete panel precast concrete building i s an extremely complex and costly undertaking, and the development of dynamic models that can represent 23 Fig. 3.1 Notched Pipe MILD STEEL STRIP 5/8*-3/4" PLATE REACTIO FRAME CROSS B E A M y TEST MODEL FOUNDATION BOLTS LOWER CONTROL ARM GAP CLOSED BY MOVING THE TEST RIG TOWARDS LOADING YOKE Fig. 3.3 Test Set Up Rig 26 a l l aspects of behaviour i s rather d i f f i c u l t i f not impossible. Very few test results have been reported for f u l l scale testing. During earthquake excitation i n e l a s t i c action w i l l in a l l likehood occur and most probably i t w i l l occur in the c r i t i c a l connection regions. A d u c t i l e connection helps to ensure the i n e l a s t i c deformation to be limited in the connection zone, thus helping to ensure a safe precast panel. Hence i t i s also assumed that the panels w i l l remain in the e l a s t i c range while non-linear behaviour is limited to the connections. 3.2 TEST SPECIMEN The s p l i t pipe connectors are prepared for testing as shown in figure 3.2. Two face plates (dimensions are shown in figure 3.2) are welded to the s p l i t pipe to allow shear forces to be applied to the test pipe during te s t i n g . A mild steel s t r i p i s welded to the face plates to f a c i l i t a t e welding of smaller diameter pipes. This s t r i p w i l l raise the contact l i n e between the pipe and the face plate. This w i l l y i e l d a better q u a l i t y of weld during testing. The face plates of the test model are equivalent to the embedded plates, angles or rebar to which the s p l i t pipe would be welded to connect two precast panels in a real precast structure. 27 3.3 TEST RIG The test r i g for the testing of s p l i t pipes i s shown in figure 3.3. A box type structure i s assembled from two rectangular mild steel side plates, a mounting plate and a back plate, which together form a closed box test assembly (photo 3.2). A base plate is welded to th i s box structure. The complete testing r i g is bolted to the r i g i d concrete test floor through holes in the base plate. These holes in the base plates are slotted to allow up to 3.0" movement p a r a l l e l to the side plates for testing pipes of various diameters. A plate is used between the top of the base plate and the foundation bolt to di s t r i b u t e the stresses due to concentrated load onto a larger area. There are a number of holes d r i l l e d in the side plates spaced at 2.0" in both horizontal and v e r t i c a l d i r e c t i o n . The holes near the mounting plate give more f l e x i b i l i t y during testing of pipes, as the mounting plate can be moved to accomodate variable pipe diameters. One of the face plates that is welded to the test specimen i s bolted to the fixed mounting plate. 3.4 LOADING YOKE The loading yoke for the test frame is shown in figure 3.4. It is assembled from a top cross beam, two side arms which are welded to the top cross beam, and a Photo 3.2 Test R i g B e f o r e M o d i f i c a t i o n s 29 o O _J s m ~* LU m ZD I— O TOP CROSS BEAM HOLE TO SUIT-1.0"0 PIN ELEVATION SIDE ELEVATION ^THREADED HOLE FOR ATTACHMENT TO 100. KIP.JACK Dimension Not ToScale P L A N Fig. 3.4 Loading Yoke-Top Cross Beam And Side Arm Detail 30 bottom cross beam. The length of two side arms i s 44.5" with forked ends hanging down. The bottom beam i s shown in figure 3.5. It is pinned to the side arms by a 1.0" diameter pin. A box is welded to t h i s bottom cross beam to provide a loading plate to which the specimen can be bolted. There are six 0.75" diameter holes through the cross beam, box and the loading plate. One of the face plates of the model is bolted to t h i s box. The loading frame was s t i f f e n e d for use with a 100 Kip. hydraulic jack. 3.5 TEST RIG MODIFICATIONS During testing of the f i f t h s p l i t pipe connection (of 2.25" diameter), rotation of the lower cross beam about the horizontal axis of the pins connecting i t , t o the side arms was observed. This was due to the e c c e n t r i c i t y between the centre l i n e of the jack and the centre of resistance of the connection. Hence, the s p l i t pipe was stressed by both a c y c l i c shear load and a c y c l i c moment. The c y c l i c moment caused squashing of the pipe at one end and pulled i t open at the other end. This moment was small for the f i r s t three tests, for which 1.0" diameter s p l i t pipe was used and the centre of resistance of test model and the centre l i n e of the loading jack almost coincided. 3 1 I 0.75" 0 BOLTS ( D E T A I L * * ) BORE P I PE LOADING P L A T E P L A N F i g. 3.5 L o a d i n g Yoke - B o t t o m C ross B e a m D e t a i l s D imens i o n Not To Scale 32 The test assembly was modified to prevent any rotation of the lower cross beam r e l a t i v e to the fixed mounting plate. A hollow rectangular control arm.. 18.0" in length, was fabricated and welded in a v e r t i c a l position to the bottom cross beam as shown in figure 3.3. A horizontal rod 1.0" in diameter was pinned at the top of the control arm to act as a link between this control arm and the reaction frame (photo 3.3-3.5). This rod, acting together with two similar control rods mounted at the l e v e l of the specimen, forms a parallelogram l i n k -age which prevents the bottom cross beam from rotating, and so eliminates c y c l i c moments a r i s i n g due to the eccentric load. This ensured that the s p l i t pipe connec-tion model was subjected to direct shear loading only. 3.6 DISPLACEMENT MEASUREMENT The shear displacements were measured by LVDT's. Two LVDT's were mounted to measure the r e l a t i v e displacement between the two face plates (figure 3.6 and photo 3.6). At the begining of each test these LVDT's were c a l i b r a t e d and c a l i b r a t i o n data was stored in a f i l e for further data processing. The LVDT's were c a l i b r a t e d by measuring the i n i t i a l and f i n a l voltages for a known displacement. This process was repeated several times and the c a l i b r a t i o n factor used was an average value. Photo 3 . 4 Test R i g A f t e r M o d i f i c a t i o n s 34 P h o t o 3.6 D i s p l a c e m e n t M e a s u r e m e n t r l m LV DT T LVDT PIN FACE PLATE BOLTED TO LOADING YOKE D LVDT HOLDER .MAGNETIC BLOCK PLATE GLUED TO -THE FACE FACE PLATE \ BOLTED TO TEST RIG TEST SPECIMEN F ig . 3.6 LVDT Mounting 36 3.7 DATA ACQUISITION SYSTEM The a p p l i e d l o a d a n d t h e c o r r e s p o n d i n g d i s p l a c e m e n t s were r e c o r d e d t o p r o d u c e t h e h y s t e r e s i s l o o p s . The d a t a a c q u i s i t i o n s y s t e m c o n s i s t e d o f two m a j o r c o m p o n e n t s : a) A NEFF s y s t e m 620 d a t a a c q u i s i t i o n s y s t e m ; b) a PDP-11/10 m i n i c o m p u t e r . T h e s e two s y s t e m s were c o u p l e d t o g e t h e r t o p r o v i d e a 64 c h a n n e l d a t a a c q u i s i t i o n s y s t e m t h a t o p e r a t e s u n d e r c o m p u t e r c o n t r o l t o m e a s u r e , p r o c e s s a n d s t o r e o u t p u t v o l t a g e s f r o m t h e t r a n s d u c e r s f i x e d on t h e t e s t m o d e l . The NEFF p r o v i d e s : a) S i g n a l c o n d i t i o n i n g f o r up t o 64 t r a n s d u c e r s ; b) s e l e c t i o n o f t h e c h a n n e l t o be m e a s u r e d ; c ) measurement o f t h e v o l t a g e f o r t h e s e l e c t e d c h a n n e l s t o r e c o r d t h e l o a d a n d d i s p l a c e m e n t ; d) d i g i t a l o u t p u t r e p r e s e n t i n g t h e v o l t a g e a n d t h e c h a n n e l s e l e c t e d . The PDP p r o v i d e s : a) C o n t r o l o f t h e NEFF, i n c l u d i n g s e l e c t i o n o f c h a n n e l t o be r e a d a n d a command t o r e a d t h a t c h a n n e l ; 37 b) processing of data from NEFF with a user written program to compute and print results for preselected channels during a tes t ; c) storage of voltage data on a disk in the PDP-11/10 minicomputer; d) some data processing c a p a b i l i t y , using output voltage values saved on disk for dif f e r e n t channels; e) provision for data f i l e transfer to the UBC Computing Centre for data processing on the MTS-G system; f) provision to stop and start the data acquisition system at any time during the te s t . The f i r s t f i v e experiments were done using a VIDAR data a q u i s i t i o n system . This data a q u i s i t i o n system can record signals for up to 50 transducers. The VIDAR can scan selected data channels for output, read output voltages for each selected channel and send data to the PDP-11/10. The NEFF and the VIDAR serve the same basic requirements for data a c q u i s i t i o n . 3.7.1 USE OF THE SYSTEM The coupled system of NEFF 620 and PDP-11/10 involves the following operations to acquire data for the tes t s . 38 3.7.1.1 OPERATION OF NEFF a) Connection of transducers to the NEFF signal conditioning module; b) use of front panel switches and an internal scanning rate switch on the NEFF 400 module. 3.7.1.2 OPERATION OF PDP-11/10 a) Preparation of one or more RK05 disks with the necessary software; b) loading and running the PDP-11/10 monitor software, RT-11; c) loading and running the BASIC software language processor; d) preparing and using a version of the general data acqu i s i t i o n program for the pa r t i c u l a r application; e) storing the data on disk for further data r e t r e i v a l ; f) processing data that has been stored on the RK05 disks; g) transmission of processed data f i l e s to the UBC Amdahl computer; h) output of hysteresis loops plotted using 39 the Amdahl computer. 3.8 LOADING PROCEDURE The specimens were loaded by a servo-controlled 100 Kip. capacity hydraulic jack (photo 3.7-3.8). Both the speed and the dir e c t i o n of the loading can be controlled by an MTS c o n t r o l l e r . The hydraulic jack can be adjusted to work on either "stroke" control or "load" control. A command signal can be generated by using an EXACT ELECTRONICS d i g i t a l function generator. Functions available from this function generator include: a) Ramp function, and; b) sine function. During the tests of s p l i t pipes a quasi-static c y c l i c load was gradually applied. The period of this loading can range from 90 msecs to 9990 hours. The loading was varied in increments of 2.5 kips. for each cycle in both di r e c t i o n s . After the load reached a selected maximum (which was a multiple of 2.5 kips.) in either d i r e c t i o n , the loading was reversed. A t y p i c a l loading sequence i s shown in figure 3.7. This process was continued u n t i l the s p l i t pipe f a i l e d . At regular intervals load and displacement voltages were read using the combination of NEFF/PDP-11/10 data Photo 3 . 8 Load C e l l 42 acquisition system. These voltage readings of displacement and load were transmitted to the PDP-11/10 mini-computer, which processed and recorded them, and also printed measured loads and displacements on a terminal typewriter. During testing, a load versus deflection curve for each s p l i t pipe was plotted continuously on an X-Y p l o t t e r . 3.9 LABORATORY TESTING Four dif f e r e n t types of pipes were used for testing. The y i e l d strength in uniaxial tension, Young's modulus, wall thickness and diameter of each pipe i s summarized in Table 3.1. A t o t a l of 25 specimens were made out of these pipes and were tested under qua s i - s t a t i c load. These are summarized in Table 3.2. Pipe lengths were 10.0", 8.0" and 6.0". Both diameter and thickness are also varied. 'During the tests i t was noted that the pipes have a tendency to f a i l along the weld between the pipe and the face plate. To try and force the pipe to f a i l along a predetermined path a notch was made at each end of the pipe, opposite to the s p l i t cut, in some specimens. These notches were 1.5" in length and 0.25" in width. This notch was made at both ends of the pipe as shown in figure 3.8. 43 TABLE 3 . 1 PIPE SPECIFICATIONS PIPE GROUP NO. OUTER DIA. OF PIPE (in.) WALL THICKNESS (i n . ) YIELD STRENGTH (ksi.) YOUNG'S MODULUS (k s i . ) 1 2 3 4 1 .00 2.00 2.25 2.00 0.125 0.125 0.250 0. 1 00 40.55 48.39 40.00 28.87 26.93 27.43 44 TABLE 3.2  RECORD OF TESTS DONE IN LABORATORY TEST CONNEC- PIPE LENGTH WIDTH NOTCH NUMBER TION SPECI- OF OF LENGTH NO. -FICA--TION PIPE SLIT 1 1-1 1 6.0" 0. 125" 2 1 -2 1 10.0" 0. 125" 3 1-3 1 10.0" 0. 125" 1 .5" 4 4-1 4 10.0" 0.125" 5 3-1 3 10.0" 0.25 " 6 3-2 3 10.0" 0.25 " 7 3-3 3 10.0" 0.25 " 1 .5" 8 3-4 3 10.0" 0.25 " 1.5" 9 3-7 3 6.0" 0.25 " 10 3-8 3 6.0" 0.25 " 1.5" 1 1 3-5 3 8.0" 0.25 " 1 2 3-6 3 8.0" 0.25 " 1.5" 1 3 2-3 2 8.0" 0.25 " 14 2-4 2 8.0" 0.25 " 1.5" 1 5 2-1 2 10.0" 0.25 " 45 1 6 2-5 2 6.0" 0.25 i t 1 7 2-2 2 10.0" 0.25 i t 1 .5" 18 2-6 2 6.0" 0.25 ?t 1 .5" 19 1-4 1 10.0" 0.25 ?t 20 1-5 1 10.0" 0.25 tt 1 .5" 21 1-6 1 8.0" 0.25 i t 22 1-7 1 8.0" 0.25 i t 1.5" 23 1-8 1 6.0" 0.25 it 24 1-10 1 6.0" 0.25 tt 1 .5" 25 1-9 1 6.0" 0.25 i t Note: An upper control arm was added to the test equipment to prevent rotation of the lower cross beam after test number 5. 46 P L A N Fig.3-8Split Pipe Connecti on 47 CHAPTER 4 GEOMETRY OF TEST RIG I n t e r a c t i o n c u r v e s a r e p l o t t e d t o c o m p a r e t h e g e o m e t r y o f t h e t e s t s e t - u p w i t h t h e b e h a v i o u r o f t y p i c a l p a n e l s i n an a c t u a l p r e c a s t b u i l d i n g . The r e l a t i o n s h i p s b e t w e e n v e r t i c a l d i s p l a c e m e n t a n d t h e s e p a r a t i o n b e tween p a n e l s ( o r b e t w e e n t h e f a c e p l a t e s o f t h e s p e c i m e n s ) a r e c o m p a r e d . 4.1 PANEL BEHAVIOUR UNDER SHEAR LOAD I n o r d e r t o s i m u l a t e t h e r e a l b e h a v i o u r i n t h e t e s t s e t up t h e b e h a v i o u r o f two p a n e l s s u b j e c t e d t o h o r i z o n t a l l o a d i s e x a m i n e d . C o n s i d e r t h e b e h a v i o u r o f two p a n e l s ABCD a n d EFGH, assumed t o be o f same d i m e n s i o n s a s shown i n f i g u r e 4.1, u n d e r t h e a c t i o n o f a h o r i z o n t a l l o a d 'P'. The p a n e l s r o t a t e t h r o u g h a n g l e s a and 0 a b o u t t h e edge A and E r e s p e c t i v e l y . The r o t a t e d p o s i t i o n s a r e AB'C'D' and EF'G'H'. A d d i t i o n a l n o m e n c l a t u r e i s g i v e n b e l o w : S° = I n i t i a l s e p a r a t i o n b e t w e e n two p a n e l s ; h = h e i g h t o f p a n e l (same f o r b o t h p a n e l s ) ; b = w i d t h o f p a n e l (same f o r b o t h p a n e l s ) ; V = r e l a t i v e v e r t i c a l d i s p l a c e m e n t b e t w e e n two 48 F i g . 4.1 R o t a t i o n of Panels Under Shear L o a d 4 9 panels; S' = variable separation between two panels; X = horizontal displacement of panels. For compatibility between the two panels the rotations a and /3 should be equal to each other. Hence the two triangles B"AE and H'EH" are similar and the included angles B"AE and H'EH" are equal to a. For B"AE Sina = V (4.1) b+S° Cosa = b+S' (4.2) b+S° For H'EH" Sina = X (4.3) h Cosa = h 2-X 2 (4.4) h Since the triangles B"AE' and H'EH" are similar, equations 4.5 and 4.6 can be written. b+S' = h 2-X 2 (4.5) b+S° h From above: S' = (h 2-X 2) (b+S°) - b h (4.6) 50 Also, X V (4.7) h b+S° X = h V (4.8) (b+S°) Subsitute for X from equation 4.8 in equation 4.5 and after s i m p l i f i c a t i o n , we get: Curves showing the re l a t i o n of the r e l a t i v e displacement V to the variable separation S' are plotted for various values of b and S°. Table 4.1 summarises the values of b and S° for which the v a r i a t i o n of S' to V i s plotted. The interaction curves are plotted in figures 4.2 and 4.3. The following observations can be made from these curves: a) These curves are independent of the height of the panel 'h'; b) these curves are dependent on the width of the panel 'b'; c) these curves are dependent on the i n i t i a l separation of the panels S° d) these curves are independent of the r a t i o b/h ; e) these curves do not depend on the absolute (b+S') 2 + (4.9) (b+S 0) 2 (b+S 0) 2 TABLE 4 . 1 INTERACTION CURVES FOR PANEL BEHAVIOUR SER. WIDTH INITIAL NO. OF SEPARA-PANEL TION S° (i n . ) (in.) 1 48.0 1 .00 2 48.0 0.75 3 48.0 0.50 4 96.0 1 .00 5 96.0 0.75 6 96.0 0.50 52 CO ^ to *^ _J UJ < -RELATIVE DISPLACEMENT B E T W E E N PANELS , V Fi g.4.2 Interact ion Graph For Pane l Behav iour 53 RELATIVE DISPLACEMENT BETWEEN PANELS, V F ig . 4.3 Interaction Graph For Panel Behaviour 54 t o t a l horizontal displacement of the panels. 4.2 TEST RIG GEOMETRY The test assembly system w i l l behave as shown in figure 4.4 under a shear load. From kinematics we can write following equations: Sina = V (4.10) Cosa =/a2-V2 (4.11) a A S =/s° - S' (4.12) S' = 7a 2-V 2 - a + S° (4.13) For V=0 S' = S° (4.14) Where: a = Length of the control arm; S° = separation of the panels in a structure; S' = reduced separation, resulting from geometry of the test r i g ; V = re l a t i v e v e r t i c a l dislacement; AS = change in separation between specimen face plates; The interaction curve obtained using equation 4.13 and the test assembly dimensions i s shown in figure 4.5. 55 CONTROL ARM. LOWER CROSS BEAM SPLIT PIPE' SPECIMEN JACK t CONTROL ROD _2S__1_ REACTION FRAME CONTROL ROD TEST RIG F ig . 4.4 Behaviour Of Test Set Up Under Shear Load 56 RELAT IVE VERTICAL SHEAR DISPLACEMENT OF S P E C I M E N S Fig. 4 5 I n te rac t i on GraphForTest Set Up Geometry 57 The r e s u l t s o b t a i n e d u s i n g e q u a t i o n 4.9 a n d 4.13 a n d u s i n g t h e t e s t s e t up d i m e n s i o n s i s p l o t t e d i n f i g u r e 4.6. T h i s i n t e r a c t i o n c u r v e u s i n g two d i f f e r e n t e q u a t i o n s y i e l d a l m o s t t h e same i n t e r a c t i o n c u r v e . F i g u r e 4.5 i s i n d e p e n d e n t o f l e n g t h o f t e s t p i p e a n d a b s o l u t e t o t a l h o r i z o n t a l d i s p l a c e m e n t o f t e s t s e t up. T h i s i n t e r a c t i o n c u r v e w i l l d e p e n d on i n i t i a l s e p a r a t i o n S°. The p r o b a b l e r a n g e o f r e l a t i v e v e r t i c a l d i s p l a c e m e n t f o r t h e t e s t a s s e m b l y was a r o u n d 0.1" a n d f o r t h i s r a n g e t h e i n t e r a c t i o n c u r v e s f o r t e s t a s s e m b l y and t h e p a n e l s a r e same. Thus t h e t e s t s e t - u p c a n s i m u l a t e t h e d e f o r m a t i o n s i m p o s e d on a j o i n t i n a c o m p l e t e b u i l d i n g w i t h p r e c a s t p a n e l s s u b j e c t e d t o s h e a r l o a d i n g . RELATIVE VERTICAL SHEAR DISPLACEMENT. V Fig-4.6 Superimposed Interaction Curves (ForTest SetUp Dimensions ) 59 CHAPTER 5 EXPERIMENTAL RESULTS The results for various connections tested in the laboratory are discussed in this chapter. The hysteresis loops for each connection are also plotted. The behaviour of each connection is b r i e f l y discussed. The resu l t s for notched and unnotched connections are also mentioned. Empirical formula for connection strength are developed and discussed. 5.1 CONNECTION RESULTS Twenty five connections were tested in the laboratory. Table 5.1 summarises the results of f a i l u r e loads, f a i l u r e displacement, and pipe dimensions. Though every e f f o r t was made to carry out the entire testing program of specimen preparation ( i . e . m i l l i n g of face plates, welding of pipe to face plates, s l i t cutting and notch cutting, loading procedure, data recording, c a l i b r a t i o n of LVDT's and testing of connections under similar conditions), i t was not possible to avoid some variations. These are discussed below. A l l the connections tested are b r e i f l y discussed in the following paragraphs. 60 TABLE 5.1 SUMMARY OF LABORATORY RESULTS CONNE- TEST LENGTH PIPE NOTCH OUTSIDE MAXI- DISPLACEMENr DIAMETER -CTION NO. OF GROUP LENGTH OF -MUM AT NO. PIPE NO. PIPE LOAD FAILURE (INS.) (INS.) (INS.) (KIPS.) (INS.) 1-1 1 6.0 1 1.0 +23.48 +0.334 -21.64 -0.110 1-2 2 10.0 1 1.0 +40.09 +0.310 -41.55 -0.350 1-3 3 10.0 1 1 .5 1 .0 +29.26 +0.200 -26.88 -0.680 1-4 19 10.0 1 1 .0 +43.52 +0.528 -42.75 -0.158 1-5 20 10.0 1 1 .5 1 .0 +30.24 +0.095 -32.33 -0.790 1 -6 21 8.0 1 1 .0 +30.04 +0.778 -31.68 -0.064 1-7 22 8.0 1 1 .5 1 .0 +19.26 +0.197 -26.53 -0.519 61 1-8 23 6.0 1 1 .0 +14.18 +0.477 -15.45 -0.0 1-9 25 6.0 1 1 .0 + 21 .70 +0.171 -23.62 -0.017 1-10 24 6.0 1 1 .5 1 .0 +14.05 +0.829 -14.28 -0.111 2-1 1 5 10.0 2 2.0 +31.05 +0.884 -30.61 -0. 149 2-2 1 7 10.0 2 1 .5 2.0 +29.86 +0.122 -31 .06 -0.338 2-3 1 3 8.0 2 2.0 +25.92 +0.946 -26.63 -0.105 2-4 1 4 8.0 2 1 .5 2.0 +20.55 +0.113 -19.00 -0.813 2-5 16 6.0 2 2.0 +25.79 +0.836 -17.67 -0.513 2-6 18 6.0 2 1 .5 2.0 +12.63 +0.877 -13.63 -0.168 62 3-1 5 10.0 3 2.25 +40.79 +0.380 -40.60 -0.010 3-2 6 10.0 3 2.25 +47.41 +0.185 -49.87 -0.818 3-3 7 10.0 3 1 .5 2.25 +50.37 +0.788 -51.56 -0.387 3-4 8 10.0 3 1.5 2.25 • +45.11 +0.738 -50.61 -0.171 3-5 1 1 8.0 3 2.25 +39.68 +0.193 -38.86 -0.354 3-6 1 2 8.0 3 1 .5 2.25 +35.45 +0.671 -41.05 -0.518 3-7 9 6.0 3 2.25 +30.60 +0.924 -35.94 -0.014 3-8 10 6.0 3 1 .5 2.25 + 22. 18 +0.303 -21.27 -0.773 4-1 4 10.0 4 2.0 0.0 0.0 0.0 0.0 5.2 PIPE GROUP 1 Specimens made out of the 1.0" diameter and 0.125" wall thick pipe of various lengths were tested in this group. A l l the specimens were made from the same piece of the pipe. For th i s pipe diameter tests on specimens 1-1, 1-2, 1-3 were c a r r i e d out before the test r i g modifications to prevent rotation of the lower cross beam were made. The rest of the tests were carried out after the test r i g modifications. For both series of tests the pipe f a i l e d at simalar load l e v e l s . 5.2.1 CONNECTION 1-1 This was the f i r s t connection tested. It was made from group 1 pipe (1.0" diameter). The 6.0" long pipe was welded between two face plates 0.625" thick. The s l i t was 0.125" wide and 6.0" long. The connection was sand blasted before the test. Because of the lack of experience in this f i r s t test, there was some slippage of the bolts holding the face plates. These bolts were tightened during the t e s t . At a load l e v e l of 20.0 Kips, the s l i t on one side was reduced from 0.125" to 0.0" as shown in figure 5.1. The connection f a i l e d during the f i f t h cycle of loading. At f a i l u r e the cracks were 1.5" to 2.0" long and 0.25" wide. This i s shown in figure 5.2 •PIPE SL IT Fig.5.1 (a) N o r m a l S l i t Of P i p e F i g . 5 . K b ) S l i t A f t e r F ew Cyc les 65 Fig.5.2 Deve l opmen tO f C r a c k F o r Unno t ched P i pe 66 and photo 5.1. The f a i l u r e load was 23.48 Kips. The f a i l u r e of the pipe was close to the weld between the face plate and the pipe. The hysteresis loops for this connection are shown in the figure 5.3. 5.2.2 CONNECTION 1-2 The second test specimen was 10.0" long. The s l i t was 0.125" wide and 10.0" long. Before the test was started a l l the bolts were tightened to prevent any slippage during the test. The connection was sand blasted before the test. At a load l e v e l of 39.7 Kips, the s l i t was s t i l l wide open, although the pipe was distorted. The c i r c u l a r section of pipe was now e l l i p t i c a l in plan (photo 5.2). The s l i t was s t i l l wide open at the load l e v e l of 41.0 Kips. During the test there was a f a i l u r e of the VIDAR data acquisition system, but no data was lost as the load and displacement values were taken from the X-Y p l o t t e r graph. The connection f a i l e d during the twelfth cycle of loading. The connection f a i l e d close to the weld again. The f a i l u r e load was 41.55 Kips. The hysteresis loops for t h i s connection are shown in figure 5.4. The crack pattern for t h i s connection at f a i l u r e was similar to figure 5.2. Photo 5.2 D i s t o r t i o n of C o n n e c t i o n 1-2 68 F i g . 5.3 H y s t e r e s i s L o o p F o r P i p e G r o u p l ( G O ' L o n g ) ( M ) 69 F i g . 5.A Hysteresis Loop For Pipe Groupl (10-0'Long) (V2) 70 5.2.3 CONNECTION NOTCHED 1-3 The t h i r d specimen was again 10.0" long. The s l i t was 0.125" wide and 10.0" long. Since both the previous tests led to f a i l u r e along the weld, i t was decided to try and i n i t i a t e the cracks at a predefined zone and so the pipe was notched at both the ends. The length of the notch was 1.5" on both sides and width of the notch was 0.125". The f a i l u r e began at the notch (photo 5.3). This is shown in figure 5.5. This f a i l u r e w i l l depend on the dir e c t i o n of the f i r s t cycle of loading. The crack began at the upper notch and grew down into the pipe (photo 5.4). During reversal of the loading-a crack started from the bottom notch also. The f a i l u r e was sudden and can occur from either notch. The opening and closing of the s l i t on the other side was not s i g n i f i c a n t . The pipe f a i l e d during eighth cycle of loading. The pipe was i n i t i a l l y very s t i f f but as the load l e v e l was increased the pipe became more and more f l e x i b l e . The f a i l u r e load for th i s connection was 29.26 Kips. The hysteresis loops for t h i s connection are plotted in figure 5.6. Comparing the hysteresis loops for the notched and the unnotched connections for th i s pipe length and group, the notched pipe can deflect nearly 20-25% more but the shear strength i s 70% of the strength of the unnotched pipe. Photo 5 . 4 C r a c k s f o r C o n n e c t i o n 1 - 3 11 / NOTCH A-—CRACK INITIATION FROM TOP ^ P I P E UNDER TEST CRACK INITIATION FROM BOTTOM Fig.5.5 Crack Propagation In Notched Pipe F i g . 5.6 Hy s te re s i s Loop For Pipe Groupl (10.0Long ) (1-3) 74 5.2.4 CONNECTION 1-4 This connection was similar to connection 1-2. Because the test r i g was modified i t was decided to retest connections similar to 1-1, 1-2, 1-3. The length of the test specimen was 10.0" and s l i t made was 0.25" wide. The f a i l u r e load was 43.52 Kips. for this connec-ti o n , compared to 41.55 Kips. for the similar connection 1-2 tested previously. The pipe f a i l e d during ninth cycle of shear load. The f a i l u r e of pipe was again along the weld between the pipe and the face plates (photo 5.5). The hysteresis loops for thi s connection are plotted in figure 5.7. The cracks before the f a i l u r e of the pipe are similar to those as shown in figure 5.2 and photo 5.6. 5.2.5 CONNECTION NOTCHED 1~5 The next connection of this group was 10.0" long with notches 1.5" long at each end of the pipe. It was similar to connection 1-3. The s l i t was 0.25" wide and 10.0" long. The f a i l u r e load was 32.33 Kips. Up to cycle number ten no cracks were noted. The cracks f i r s t appeared on the bottom side of the pipe and intruded into the pipe length towards the top notch. The f a i l u r e was sudden and noisy. The data a q u i s i t i o n system f a i l e d during the experiment, but data from the X-Y plot was used Photo 5 . 6 Crack P a t t e r n f o r C o n n e c t i o n 1-4 7 6 F i g . 5.7 Hy s te re s i s Loop For Pipe Group 1 (1Q0"Long) (1-4 ) 77 to provide the missing data. The hysteresis loops for this connection are plotted in figure 5.8. 5.2.6 CONNECTION 1-6 The next connection tested from t h i s group was 8.0" long with no notches. The f a i l u r e f a i l u r e load was 31.68 Kips. The f a i l u r e was sudden and the test specimen f a i l e d close to the weld between the pipe and the face plate (photo 5.7-5.8). The f a i l u r e occured during the eighth cycle of shear loading. Upto a load l e v e l of 20.0 Kips. there were no cracks. The hysteresis loops for t h i s connection are plotted in figure 5.9. 5.2.7 CONNECTION NOTCHED 1-7 The next test specimen was also 8.0" long, but had notches 1.50" long at each end of the pipe. The s l i t width was 0.25". The cracking f i r s t started near the notch. The f a i l u r e pattern for thi s connection tested i s shown in figure 5.10 and photo 5.9. The pipe f a i l e d during seventh cycle of shear loading. The shear load for this pipe was 26.53 Kip. and the corresponding shear def l e c t i o n was 0.519". The hysteresis loops for this connection are plotted in figure 5.11. 7 8 F i g . 5.8 H y s t e r e s i s Loop F o r p j p e Groupl ( &.0"Long) (1-5) Photo 5.8 Failure of Connection 1-6 80 F i g . 5.9 Hy s te re s i s Loop For p j p ( ? Group 1 (80"Long}-(1-6 ) NOTCHED PIPE CRACK PATTERN NOTCH Fig. 5.10 Crack PatternFor Notched Pipe Photo 5.9 F a i l u r e of C o n n e c t i o n 1-7 83 F i g . 5-11 Hys te re s i s Loop For Pipe Groupl ( 8.0"Long) ( 1 - 7 ) 8 4 .5.2.8 CONNECTION 1-8 The next test specimen was an unnotched pipe, 6.0" long made out of pipe group 1. This connection was similar to connection 1-1. The pipe f a i l u r e was sudden and the hysteresis loops (figure 5.12) obtained were quite peculiar for thi s connection. Also i t was noted that the f a i l u r e of this test specimen was not from the edge of the face plate and the test specimen as most of the unnotched pipe specimens behaved, but the f a i l u r e started from the center of the pipe. Later i t was found that the test r i g was not aligned properly and i t was decided to repeat t h i s test in the laboratory. The shear f a i l u r e load was 15.45 Kips. 5.2.9 CONNECTION 1-9 This connection tested was a repeat of connection previously tested. The f a i l u r e load was 23.62 Kips. The pipe f a i l e d during tenth cycle of shear loading. The hysteresis loops plotted for thi s connection are shown in figure 5.14. The crack pattern at f a i l u r e i s shown in figure 5.13. 85 F i g . 5.12 Hysteresis Loop For PipeGroupl (6.0Long) (1-8) 86 ,CRACKS 1.5*LONG A N D 0.25'WIDE F ig.5.13Development Of Crack For Unnotched P ipes A f t e r Test R ig M o d i f i c a t i o n s 87 F i g . 5 .H Hy s te re s i s Loop For Pipe Groupl (6.0'Long) (1-9 ) 88 5.2.10 CONNECTION NOTCHED 1-10 The last test specimen of thi s series was again 6.0" long and 1.0" in diameter. The pipe had a s l i t which was 0.25" wide and two notches which were 1.5" long and 0.25" wide. The f a i l u r e load was 14.28 Kips. Between cycle five and six the shear d e f l e c t i o n was 0.072". There was no closure of the s l i t . The pipe f a i l e d during the ninth cycle of shear loading. The hysteresis loops for this connection are plotted in figure 5.15. The f a i l u r e of the pipe was again along a l i n e between the notches. 5.3 PIPE GROUP 2 Specimens made out of the 2.0" diameter and 0.125" wall thickness pipe of various lengths were tested in thi s group. Testing of this series was done after the test r i g modifications which prevented rotation of the bottom cross beam. Both notched and unnotched connections were tested. 5.3.1 CONNECTION 2-1 This connection specimen was 10.0" long with a pipe diameter of 2.0". The pipe thickness was 0.125" 89 F i g . 5.15 Hy s te re s i s Loop For Pipe Groupl (6.0"Long) ( M O ) 90 and width of s l i t was 0.25". There was no notch in this test connection specimen. The pipe f a i l e d at a load le v e l of 31.05 Kips. and the corresponding shear deflection was 0.884". The pipe f a i l e d during the twelfth cycle of shear loading. Since there was no notch on the back side of pipe the f a i l u r e occured near the weld between the face plate of the test specimen and the pipe (photo 5.10). The f a i l u r e was sudden with a loud noise. The hysteresis loops for t h i s connection are plotted in figure 5.16. 5.3.2 CONNECTION NOTCHED 2-2 The next in this series of 2.0" diameter pipe was a 10.0" long connection. The s l i t was 0.25" wide and pipe thickness was 0.125". Notches 1.50" long were made in thi s pipe opposite the s l i t . The f a i l u r e load for this test specimen was 31.06 Kips. The f a i l u r e was sudden and the cracks i n i t i a t e d from the edges of the notch and moved into the pipe. The pipe f a i l e d during the f i f t e e n t h cycle of shear loading and shear deflection was 0.338". The hysteresis loops for this connection are plotted in figure 5.17. Photo 5.10 Failure of Connection 2-1 92 F i g . 5.16 Hy s te re s i s Loop For PipeGroup2 (10.0'long) (2-1) 93 F i g . 5 .17 H y s t e r e s i s Loop F o r P i p e G r o u p 2 ( 10.OL.ong) ( 2 - 2 ) 94 5.3.3 CONNECTION 2-3 The next connection of this group was 8.0" long. The s l i t was 0.25" wide. The f a i l u r e load was 25.1077 Kips. The f a i l u r e of thi s connection occured suddenly. There was a sl i g h t discrepancy between the recorded values of load and displacement and the values plotted on the X-Y recorder. This error may have crept in because of the change in c a l i b r a t i o n factor of the X-Y p l o t t e r . The LVDT's were c a l i b r a t e d before each test and i t i s to be noted that the plotted values on the X-Y plo t t e r are generally used only as a reference for reversal of loading, and the graph plotted on X-Y plotter i s therefore not very important. The pipe f a i l e d during the twelfth cycle of loading. The shear f a i l u r e load was 26.63 Kips. The hysteresis loops for thi s connection are plotted in figure 5.18. 5.3.4 CONNECTION NOTCHED 2-4 This connection was 8.0" long with a s l i t 0.25" wide. Notches 1.5" long were made in thi s test specimen. The f a i l u r e shear load was 20.55 Kips. At a load l e v e l of 14.0 Kips. the c i r c u l a r cross section of the pipe was distorted (photo 5.11). Before the start of th i s experiment the X-Y plotter was c a r e f u l l y c a l i b r a t e d 95 F i g . 5.18 H y s t e r e s i s Loop For PipeGroup2 (8.0"Long) (2-3) Photo 5.11 D i s t o r t i o n of C o n n e c t i o n 2-4 97 and during the test good agreement between plotted and computed values was noted. The f a i l u r e of the pipe was sudden and there was no warning. The pipe got ripped and tore off from the notch. The hysteresis loops for this connection are plotted in figure 5.19. The pipe f a i l e d during eleventh cycle of shear loading. 5.3.5 CONNECTION 2-5 The pipe length for t h i s connection was 6.0" with an outer diameter of 2.0". The width of s l i t was 0.25" and the wall thickness was 0.125". No notch was made on the back side of the pipe. T i l l the end of f i f t h cycle and a load level of 14.0 Kips. there were no f a i l u r e cracks, although the pipe had lost i t ' s c i r c u l a r cross section (photo 5.12). The f a i l u r e load for t h i s connection was 25.79 Kips. The pipe f a i l e d after the seventh cycle. During the eighth cycle an attempt was made to load the pipe by another c y c l i c shear load, but the cracks developed were too wide and deformations had entered in the p l a s t i c stage. The hysteresis loops for th i s connection are plotted in figure 5.20. 5.3.6 CONNECTION NOTCHED 2-6 The last connection made from 2.0" diameter F i g . 5.19 Hy s te re s i s Loop For PipeGroup2 (S.OLong) (2-4) Photo 5.12 Di s t o r t i o n of C o n n e c t i o n 2-5 100 F i g . 5.20 Hys te re s i s Loop For PipeGroup2 (6.0'iong) (2-5) 101 pipe was 6.0" long, with notches 1.50" long opposite to the 0.25" wide s l i t . No cracks were noted up to a load l e v e l of 10.0 Kips. The pipe f a i l e d during ninth cycle of shear loading and the shear load before f a i l u r e was 13.63 Kips. It was noted that the deformation was severe along the notch and the pipe f a i l e d along a l i n e between the notches with a loud noise. The hysteresis loops for thi s connection are plotted in figure 5.21. 5.4 PIPE GROUP 3 Specimens made out of the 2.25" diameter and 0.25" wall thick pipe of various lengths were tested in th i s group. In a l l eight tests were carried out in this s e r i e s . One test (connection 3-1) was done before the test r i g modification, which prevented rotation of the lower cross beam, and the rest of them were done after the r i g modification. 5.4.1 CONNECTION 3-1 A 10.0" long test specimen was the f i r s t connection tested in th i s group. The s l i t size was increased from 0.125" to 0.25" to make the connection more f l e x i b l e . The increase in s l i t size w i l l permit more deformations and the s l i t walls w i l l not touch each other 1 02 F i g . 5.21 Hys te re s i s Loop For Pipe Group2 (6.fJLong) (2-6) 1 03 at a low load l e v e l . The length of the s l i t was 10.0". The position of LVDT's was changed for t h i s t e s t . The LVDT's were now mounted on a plate glued to the face plate of the test specimen that was bolted to the fixed mounting plate. Due to the increase in pipe diameter the centre of loading of jack might have sh i f t e d . This e c c e n t r i c i t y of load might have induced c y c l i c moments. At a load l e v e l of 40.0 Kips. a f a i l u r e of the pipe close to the weld was noted at the bottom of pipe. The pipe was under heavy compression at top and i t was highly d i s - t o r t e d . This i s shown in figure 5.22. This might have been caused by rotation of bottom cross beam, since the upper control arm was not f i t t e d when this test was made. The f a i l u r e was again noted along the weld between the pipe and the face plate (photo 5.13). Wide cracks were noted at the top of the pipe. The f a i l u r e of the connection occured during the twelfth cycle of shear loading. The f a i l u r e load was 40.79 Kips. The hysteresis loops for th i s connection are plotted in figure 5.23. 5.4.2 CONNECTION 3-2 The test was a repeat of the test on connection 3-1. There were problems of data recording hence i t was decided to repeat t h i s test. The data recording system was changed from VIDAR to NEFF. SHEAR FAILURE ALONG THE WELD o < o Q ' Fig.5.22 F a i l ur <? Of Unnotched Pipe Under Shear Load 105 F i g . 5.23 Hy s te re s i s Loop _For PipeGroup3 (ICLOLong) (3-1) 1 06 The NEFF system is more advanced than VIDAR. The test r i g was modified to prevent any rotation of the lower cross beam during loading. The pipe was 10.0" long and 0.25" thick. During the f i f t e e n t h cycle of shear loading and a load l e v e l of 47.0 Kips. the f i r s t crack was noted at top of the pipe. On reversal of loading second crack was noted at the bottom of pipe. The cracks which i n i t i a t e d between f i f t e e n t h and sixteenth cycle started lengthening into the pipe. This lengthening of the crack was along one edge only as shown in figure 5.13. The shearing f a i l u r e was sudden and the rotation of the pipe was minimum. The face plates of test specimen did not rotate at a l l . The f a i l u r e load was 49.87 Kips. The hysteresis loops for t h i s connection are plotted in figure 5.24. The f a i l u r e of the test specimen was during the twentieth cycle. 5.4.3 CONNECTION NOTCHED 3~3 This connection was 2.25" diameter pipe and 10.0" long. The s l i t was 0.25" wide and 10.0" long. Two notches were made diametrically opposite to the s l i t at the top and bottom of the pipe. The notches were 1.5" long and 0.25" wide. The f i r s t crack began at the upper notch. The second crack was noted at the lower notch. Before f a i l u r e there was a single crack, starting at each 107 F i g . 5.24 Hy s te re s i s Loop For PipeGroup3 (lO-OLong) (3-2) 1 08 notch. The rotation of the face plate and the lower cross arm was minimum and the f a i l u r e was sudden and with a loud noise. The hysteresis loops for this connection are p l o t t t e d in figure 5.25. The f a i l u r e occured during the eleventh cycle of shear loading. The f a i l u r e load was 51.56 Kips. 5.4.4 CONNECTION NOTCHED 3~4 This connection was similar to the previously tested notched connection number 3-3. The pipe tested in the previous test was distorted to a large extent and therefore • the same dimension pipe was tested again to study the behaviour of 10.0" long pipe under c y c l i c shear load. The pipe f a i l e d during the twenty second cycle of shear loading. The cracks started around eighteenth cycle. The f i r s t crack was at the upper notch at a load l e v e l of 46.0 Kips. During twentyth cycle a crack started at the lower notch and the load l e v e l was 47.0 Kips. This pipe was not sand blasted and at the surface of pipe tension cracks were noted near the notches which are highly stressed. The crack started to lengthen from bottom notch and the pipe f a i l e d at a load l e v e l of 50.61 Kips. • The displacement at f a i l u r e of pipe was 0.738". The hysteresis loops for this connection are plotted in figure 5.26. 109 F i g . 5.25 Hy s te re s i s Loop For Pipe Group3 (10.0"Long) (3-3) 1 1 0 F i g . 5.26 H y s t e r e s i s Loop For PipeGroup3 (100"Long) (3-4) 111 5.4.5 CONNECTION 3~5 This connection was 8.0" long test specimen with wall thickness of 0.25". The diameter of the pipe was 2.25" and the s l i t width was 0.25". The t o t a l number of cycles required for pipe f a i l u r e was thirteen. The f a i l u r e load was 39.68 Kips. The hysteresis loops for this connection are plotted in figure 5.27. There were no cracks developed upto the tenth cycle, but the pipe lost i t ' s c i r c u l a r shape around eighth cycle, and at a load level of 12.90 Kips. (photo 5.14). Slight cracks were noted simultaneously both at top and bottom around eleventh cycle. The shear f a i l u r e was along the weld between the pipe and the face plate. The f a i l u r e occured with a loud noise. 5.4.6 CONNECTION NOTCHED 3~6 This connection was 8.0" long with an over a l l pipe diameter of 2.25". The wall thickness was 0.25" and s l i t width was 0.25". Notches were made at the top and bottom- of the pipe. Up to the twelfth cycle for th i s test no cracks were noted. Also the notches were l e f t undisturbed. Around cycle fourteen the pipe was distorted. The c i r c u l a r cross section became approximately e l l i p t i c a l , the s l i t at the bottom of the Photo 5.14 D i s t o r t i o n of C o n n e c t i o n 3-5 113 F i g . 5.27 H y s t e r e s i s Loop For Pipe Group 3 (80"Long) (3-5) 1 1 4 p i p e c l o s e d and c r a c k s were o b s e r v e d a t t h e i n n e r e n d o f t h e t o p n o t c h . Upon r e v e r s a l o f t h e l o a d c r a c k s were n o t e d a t t h e b o t t o m n o t c h and t h e c r a c k s p r o p a g a t e d a l o n g t h e s e c r a c k s and p i p e f a i l e d w i t h a h e a v y n o i s e . The t e s t s p e c i m e n f a i l e d d u r i n g t h e e i g h t e e n t h c y c l e o f l o a d i n g . The s h e a r f a i l u r e l o a d was 41.05 K i p s . The h y s t e r e s i s l o o p s f o r t h i s c o n n e c t i o n a r e p l o t t e d i n f i g u r e 5.28. 5.4.7 CONNECTION 3-7 T h i s c o n n e c t i o n was 2.25" i n d i a m e t e r and 6.0" i n l e n g t h . The s l i t was 0.25" w i d e and 6.0" l o n g . P i p e t h i c k n e s s was 0.25". T h e r e were no n o t c h e s . D u r i n g p l o t t i n g o f h y s t e r e s i s l o o p s k i n k s were n o t e d ( s e e f i g u r e 5 . 2 9 ) . T h e s e k i n k s o c c u r e d due t o s l i p b e t w e e n t h e m o u n t i n g p l a t e o f t e s t r i g a n d t h e t e s t r i g . The l o a d c a r r y i n g c a p a c i t y was n o t a f f e c t e d . A r o u n d t h e e i g h t h c y c l e d i s t o r t i o n o f t h e p i p e s t a r t e d a n d t h e f i r s t c r a c k was n o t e d a t t h e t o p o f t h e p i p e a t t h e n i n t h c y c l e o f l o a d i n g . The l o a d l e v e l was 24.67 K i p s . A b o t t o m c r a c k was n o t e d a r o u n d t h e t e n t h c y c l e a n d t h e f a i l u r e o c c u r e d f r o m b o t t o m . The l o a d l e v e l a t f a i l u r e was 35.94 K i p s . The f a i l u r e o f p i p e o c c u r e d a t e l e v e n t h c y c l e o f c y c l i c l o a d i n g a n d f a i l u r e c r a c k s a r e shown i n p h o t o 5.15 and 5.16. 1 \ 5 IT) F i g . 5 . 2 8 H y s t e r e s i s Loop For P i p e G r o u p 3 ( 8 0 L o n g ) (3 -6) 1 16 F i g . 5.29 Hy s te re s i s Loop For Pipe G r o u p 3 ( f c f JLong) (3-7) Photo 5.15 F a i l u r e of C o n n e c t i o n 3-7 Photo 5.16 F a i l u r e of C o n n e c t i o n 3-7 1 18 5.4.8 CONNECTION NOTCHED 3-8 The eighth connection in this series was 2.25" diameter pipe, 6.0" long, 0.25" thick and a s l i t width of 0.25". Two notches were cut at opposite ends of the pipe. The notches were 1.5" long and 0.25" wide. The f a i l u r e was a sudden shear f a i l u r e , with l i t t l e warning. In between observations showed that the pipe's c i r c u l a r p r o f i l e was distorted after three or four cycles of loading. The t o t a l number of cycles of loading to f a i l u r e was nine. The f a i l u r e load was 22.18 Kips. and the displacement at f a i l u r e was 0.773". The hysteresis loops for this connection are plotted in figure 5.30. The pipe's d u c t i l i t y was more pronounced than for the connection 3-7, which had i d e n t i c a l dimensions, without the notches. This improved d u c t i l i t y i s attributed to the notches in connection 3-8. 5.5 PIPE GROUP 4 The fourth type of pipe used for the testing program was 2.0" in diameter, with 0.1" wall thickness. Only one test was carried out, and thi s was made before the test r i g was modified to prevent rotation of the lower cross beam. 119 F i g . 5.30 H y s t e r e s i s Loop For Pipe Group 3 ( 60"Long) (3-8) 1 20 5.5.1 CONNECTION 4-1 The connection made out of this pipe was 10.0" long. The s l i t was 0.125" wide and 10.0" long. The pipe thickness was 0.1". The pipe f a i l e d during i n s t a l l a t i o n of the specimen in our testing r i g . The f a i l u r e occured during the alignment of the bolts to the loading yoke and pipe deformed a lot to render the specimen not f i t for testing. No more pipe of this type was tested during the test program. 5.6 TEST RESULTS Based on the test data from the experiments calculations of the strength, s t i f f n e s s e s , maximum p l a s t i c deflections and d u c t i l i t y are summarised in the following sect ions. 5.6.1 STRENGTH OF PIPES The maximum positi v e or negative loads c a r r i e d by each connection are obtained from the hysteresis loops. These loads are summarised in table 5.1. For most of the notched pipes the average f a i l u r e shear load was about 75.0% of that of the unnotched pipes. A 1.0" or smaller diameter pipe when used as a connection 121 w i l l apparently have a higher f a i l u r e load than a pipe of 2.0" or more for the same wall thickness. The shear strength of a connection w i l l be increased by using a larger wall thickness. 5.6.2 STIFFNESS CALCULATIONS The st i f f n e s s e s of a l l the pipes were worked out by plate analogy and from the hysteresis loops of the d i f f e r e n t connections. For plate analogy the curved surface of the pipe i s developed to be a f l a t plate and i t is assumed that plane s t r a i n conditions pre v a i l and then using the basic equations of e l a s t i c i t y the shear s t i f f n e s s e s are worked out. These s t i f f n e s s e s are tabulated in Table 5.2. The experimental stiffnesses are calulated from the straight l i n e regions of the loops. These sti f f n e s s e s are worked out for connection 1-2 between points A and B of the hysteresis loops of figure 5.4. This process i s repeated for a l l the connections. Stiffnesses found using the plate analogy are higher for a l l the connections, especially for the notched connections. 1 22 5.6.3 DEFLECTION RESULTS Table 5.3 summarises the e l a s t i c and the maximum p l a s t i c deflections of the notched and the unnotched pipes. The maximum p l a s t i c deflections are calculated from the hysteresis loops. The maximum p l a s t i c deflection i s taken as the highest value for which the connection w i l l s t i l l carry c y c l i c load for another half cycle with increased d e f l e c t i o n . The e l a s t i c d e f l e c t i o n i s calculated using the e l a s t i c s t i f f n e s s of each connection as shown in table 5.2 and the maximum f a i l u r e load as taken from table 5.1. For four cases the maximum deflection for notched pipes was twice of that of unnotched pipes. There was only one case (connection 2-5 and 2-6) where the deflection of the notched connection was less than that of the unnotched connection. 5.6.4 DUCTILITY CALCULATIONS The d u c t i l i t y of a structure or a connection is defined as the r a t i o of the maximum p l a s t i c d e f l e c t i o n before f a i l u r e to the e l a s t i c d e f l e c t i o n , calculated as described above. These deflections are summarised in table 5.3. Table 5.4 tabulates the d u c t i l i t y found for these pipes. Except for connection 2-3, the d u c t i l i t y of these s p l i t pipe connections is more than 10. Table 5.5 1 23 shows the deflections for a given d u c t i l i t y of 4 and 10. A l l connections except 2-3 w i l l s t i l l continue to dissipate energy under c y c l i c loading with d u c t i l i t y in excess of 10. The s p l i t pipes are quite d u c t i l e in general, the maximum observed d u c t i l i t y being 40.5, but the notched pipes are generally more ductile than the unnotched pipes tested in the laboratory. For connections 2-3 and 2-4, the d u c t i l i t y of the notched pipe is more than twice the d u c t i l i t y of the unnotched pipe. For connections 1-6 and 1-7 the notched connection had 1.95 times the d u c t i l i t y of the unnotched connection. The d u c t i l i t y for notched connection number 2-6 is lower by 26.85% than unnotched connection number 2-5 for the same length of the pipe. The increased d u c t i l i t y for pipe group 3 for notched pipes compared to unnotched pipes varies from 12.00% to 74.00%. ELASTIC TABLE 5.2 STIFFNESSES OF CONNECTIONS CONNEC- TEST PLATE EXPERIMENTAL T I O N NO. ANALOGY STIFFNESS NO. STIFFNESS 1-1 1 6301.45 4856.00 1-2 2 10502.41 10566.70 1-3 3 10108.42 4941.60 1-4 19 10502.41 8231.06 1-5 20 9742.91 6234.80 1-6 21 8401.93 6825.94 1 -7 22 7575.21 4247.74 1-8 23 6301.44 4084.28 1-9 25 6301.44 3488.94 1-10 24 5331.66 2787.31 2-1 15 4571.78 2966.85 2-2 1 7 4411.30 3549.28 2-3 13 3657.42 1903.76 2-4 1 4 3480. 18 3242.01 2-5 16 2743.07 2126.61 1 2 5 2 - 6 18 2 5 2 8 . 4 5 9 7 7 . 2 0 3-1 5 8 7 3 1 . 2 4 5 0 6 4 . 1 5 3 - 2 6 8 7 3 1 . 2 4 5 3 4 4 . 8 7 3 - 3 7 8 4 4 3 . 2 8 4 7 5 6 . 6 7 3 - 4 8 8 4 4 3 . 2 8 4 4 8 7 . 8 2 3 - 5 1 1 6 9 8 5 . 0 0 4 9 8 6 . 2 8 3 - 6 1 2 6 6 6 6 . 6 8 3 4 9 1 . 1 1 3 - 7 9 5 2 3 8 . 7 5 2 4 8 1 . 8 4 3 - 8 1 0 4 8 5 2 . 5 9 1 5 6 9 . 2 4 4 - 1 4 0 . 0 0 0 . 0 0 TABLE 5.3 ELASTIC DEFLECTIONS AND PLASTIC DEFLECTIONS CONNEC- TEST ELASTIC PLASTIC TION NO. DEFLECTION DEFLECTION NO. 1-1 1 0.004835 0.1068 1-2 2 0.003932 0. 1 20 1-3 3 0.005921 0.240 1-4 1 9 0.005287 0. 1 50 1-5 20 0.005185 0. 1 50 1-6 21 0.004641 0.075 1 -7 22 0.006246 0. 1 97 1-8 23 0.003783 ~ 0.090 1-9 25 0.006770 0.130 1-10 24 0.005123 0.1110 2-1 1 5 0.010465 0. 1 30 2-2 1 7 0.008752 0. 1220 2-3 1 3 0.013988 0.1050 2-4 1 4 0.006339 0.1130 2-5 16 0.012127 0.2000 1 27 2-6 18 0.013948 0.1680 3-1 5 0.008055 0. 1 50 3-2 6 0.009330 0. 170 3-3 7 0.010840 0.350 3-4 8 0.011277 0.230 3-5 1 1 0.007958 0. 1 20 3-6 12 0.011758 0.300 3-7 9 0.014481 0. 1 60 3-8 1 0 0.014134 0.250 4-1 4 0.00 0.00 TABLE 5.4 DUCTILITY OF NOTCHED AND UNNOTCHED PIPES CONNEC- TEST NOTCH/ DUCTILITY TION NO. UNNOTCH NO. 1-1 1 U 22.09 1-2 2 U 30.52 1-3 3 N 40.53 1-4 19 U 28.37 1-5 20 N 28.93 1-6 21 U 16.16 1 -7 22 N 31 .54 1-8 23 U 23.80 1-9 25 U 19.21 1-10 24 N 21 .67 2-1 1 5 U 12.43 2-2 1 7 N 1 3.94 2-3 1 3 U 7.50 2-4 1 4 N 17.83 2-5 1 6 U 1 6.50 1 29 2-6 18 N 12.07 3-1 5 U 18.62 3-2 6 U 18.22 3-3 7 N 32.29 3-4 8 N 20.40 3-5 1 1 U 1 5.08 3-6 1 2 N 25.52 3-7 9 U 1 1 .05 3-8 1 0 N 17.70 4-1 4 U 0.00 1 30 TABLE 5.5 DEFLECTIONS FOR DIFFERENT DUCTILITY CONNEC- TEST DEFLECTION DEFLECTION T I O N NO. FOR FOR NO. DUCTILITY 4 DUCTILITY 10 1-1 1 0.019340 0.04835 1-2 2 0.015728 0.03932 1-3 3 0.023684 0.05921 1-4 19 0.021148 0.05287 1-5 20 0.020740 0.05185 1 -6 21 0.018564 0.04641 1-7 22 0.024984 0.06246 1-8 23 0.015132 0.03783 1-9 25 0.027080 0.06770 1-10 24 0.020492 0.05123 2-1 15 0.041864 0.10466 2-2 17 0.035008 0.08752 2-3 13 0.055952 0.13988 2-4 1 4 0.025356 0.06339 2-5 16 0.048508 0. 12127 131 2-6 18 0 . 0 5 5 7 9 2 0 . 1 3 9 4 8 3-1 5 0 . 0 3 2 2 2 0 0 . 0 8 0 5 5 3-2 6 0 . 0 3 7 3 2 0 0 . 0 9 3 3 0 3-3 7 0 . 0 4 3 3 6 0 0 . 1 0 8 4 3-4 8 0 . 0 4 5 1 0 8 0 . 1 1 2 7 7 3-5 1 1 0 . 0 3 1 8 3 2 0 . 0 7 9 5 8 3-6 12 0 . 0 4 7 0 3 2 0 . 1 1 7 5 8 3-7 9 0 . 0 5 7 9 2 4 0.14481 3-8 1 0 0 . 0 5 6 5 3 6 0 . 1 4 1 3 4 4-1 4 0.00 0.00 CHAPTER 6 DISCUSSION, CONCLUSIONS AND FUTURE SCOPE The results of the present investigation are summarized in thi s chapter. Conclusions based on the experimental observations and the behaviour of the connections are b r i e f l y mentioned. The scope of the future investigations is also highlighted. 6.1 DISCUSSION AND CONCLUSIONS This investigation was i n i t i a t e d to develop and study the behaviour of a d u c t i l e connection for precast concrete structures. It was assumed in the testing of these connections that the precast panels remain e l a s t i c while the non-linear behaviour i s r e s t r i c t e d to the connection. The behaviour of s p l i t pipe connections i s discussed in the following sections. 6.1.1 STRENGTH OF PIPE Based on the observations and the results for the experiments carried out in the laboratory, an empirical formula for shear capacity can be proposed. The f a i l u r e load of the unnotched and notched pipes i s a 1 33 function of: a) Length of the pipe; b) diameter of the pipe; c) cross sectional area of the pipe; d) y i e l d strength of the pipe in shear; e) length of the notch. Figure 6.1 shows the variation of the f a i l u r e shear load divided by the- uniaxial y i e l d strength in tension with variation in the e f f e c t i v e shear area, which is taken as the product of the wall thickness and the length of the pipe (less the length of any notches). Based on these graphs and the observations, a lower bound to the f a i l u r e load of the pipe can be expressed as: F = k*Y*(L-2n)*t (6.1) Where: F = Shear strength of the pipe; Y = y i e l d strength of the pipe; L = length of the pipe; n = length of a notch; t = thickness of the pipe; k = a constant proposed to be 0.50; The above formula works quite well with only one 134 value on the graph which is way out (connection 3-1). It was noted during the experiment that this pipe f a i l e d prematurely and hence the pipe's strength is far below the normal strength. Most of the hysteresis loops were well defined and there was no pinching of these loops. The greater the length of the s p l i t pipe the higher w i l l be the f a i l u r e shear load of the connection. The notches made in the s p l i t pipe reduce the shear load capacity of the connection due to the reduction in shear r e s i s t i n g area of the s p l i t pipe. It appears that strength f a l l s with increasing diameter as shown by the strength for the 10.00" unnotched connection specimens 1-4 and 3-1 which had maximum strength of 43.52 Kips. and 40.79 Kips, respectively, even although the wall thickness of 3-1 was twice that of 1-4. It appears from photograph 7.14 (connection 3-5) that pipes of 2.25" diameter may f a i l by buckling and the f u l l potential strength capacity of the pipe may not be reached before f a i l u r e . 6.1.2 STIFFNESS OF PIPE Calculated s t i f f n e s s e s are shown in figures 6.2 and 6.3. The s t i f f n e s s of pipe w i l l depend on the length and the thickness of the pipe. There w i l l be a reduction of s t i f f n e s s of the pipe for an increase in pipe diameter. It i s assumed here that the s t i f f n e s s varies 1 35 with thickness of the pipe and hence the sti f f n e s s e s plotted for the 2.25" pipe (group 3) are reduced by half, because the wall thickness of this pipe i s 0.25", while the thickness of pipe group 1 and 2 i s 0.125". For those tests that were repeated for similar connections, the sti f f n e s s e s plotted are average values. Figure 6.2 shows the va r i a t i o n of s t i f f n e s s with the length of the pipe. It can be seen that the s t i f f n e s s of pipe increases with an increase in length of the connection. Figure 6.3 shows that s t i f f n e s s tends to decrease with an increase in pipe diameter. 6.1.3 DEFLECTION OF PIPE The maximum deflections are worked out from the hysteresis loops as discussed in section 5.6.3 and are plotted in figure 6.4 for di f f e r e n t pipe diameters. The data for deflection of the 2.0" diameter pipe group appears to be inconsistent, and there is a considerable scatter in the other plotted values. None the les s , i t is suggested that the maximum deflections incurred by the connections are independent of the length of the pipe but vary inversely with the diameter of the pipe. The 2.25" diameter pipes have deflections that are approximately twice those of the 1.0" diameter pipes tested in the laboratory. The scatter of the results i s primarily due 1 36 to the fact that the experimental technique uses load as the parameter that was increased in a systematic way for successive cycles. Therefore not a l l specimens were tested so as to maximise the deflection at f a i l u r e . 6.1.4 DUCTILITY OF PIPE D u c t i l i t y is discussed in section 5.6.4, and results are given in table 5.4. Both the unnotched and the notched connections behaved in a du c t i l e fashion before they f a i l e d along the weld or along the notches. D u c t i l i t y of these s l i t pipes appears to depend on the length of the pipe with very l i t t l e effect of the diameter or the thickness of the pipe, as shown in figure 6.5. There appears to be a reduction of d u c t i l i t y of about 35% for every 2.0" reduction in length of the pipe for pipe group 1 and 3. This reduction in d u c t i l i t y is not v a l i d for pipe group 2. The notches on both ends tend to make the s p l i t pipes more duc t i l e by about 30-35% as discussed in the previous chapter, but for pipe diameters of 2.0" or more there appears to be no s i g n i f i c a n t reduction of load capacity. Notched and unnotched connections fabricated from pipes of 2.0" diameter or more, with pipe lengths of 10.0", tend to f a i l at approximately the same load, but the d u c t i l i t y of notched pipes i s greater (see connection 2-1 and 2-2, and connection 3-2 and 3-3). Thus the 1 37 notches appear to be advantageous, and 10.0" long connection with notches seems to be a good choice for a s p l i t pipe connection. It is believed that longer pipe lengths may give even more d u c t i l i t y along with higher f a i l u r e loads. However i t i s advisable to rely on a r e l a t i v e l y large number of s p l i t pipe connections of say 8.0"-10.0", rather than fewer longer connections. 6.1.5 RECOMMENDATION FOR DETAIL CONNECTION DESIGN The notches should be made at both ends to make the pipe f l e x i b l e . During the experimental study the variation of notch width was not taken into consideration. However a 0.25" notch width i s recommended. The longitudinal s l i t cut along the length of the pipe w i l l allow the connection to deform under shear loading and to dissipate energy generated under c y c l i c loading. Sligh t inaccuracies in dimensions of the precast panels during casting can be accomodated when the pipe i s welded in position on s i t e . Volume changes in the panels due to the temperature and the shrinkage of the concrete can be e a s i l y accomodated by the s p l i t pipe. The s p l i t pipe connection is simple to complete, and the 1 38 f i e l d welding is a r e l a t i v e l y fast empirical formula proposed for strength cases and is conservative except in one 6.2 FUTURE SCOPE The research described in t h i s d i s s e r t a t i o n meets but a small part of the o v e r a l l objective of predicting the behaviour of precast concrete buildings under earthquake loads, and the research in this' f i e l d i s only begining. Two face plates were used to weld the pipe during the t e s t . Certainly there is a strength contribution from them. An attempt should be made to determine the strength contribution of these plates. Testing should be extended to longer connections, and the e f f e c t of d i f f e r e n t notch sizes and placements could also be investigated. It should also be noted that in practice i t i s unlikely that the-welds would be made at opposite ends of a diameter as they were in these tests. In actual use i t i s more common for the welds to be closer to the s l i t in the pipe. The effect of t h i s should also be studied. This s p l i t pipe connection w i l l be a good f i n i t e element analysis topic, although the problem is very sensitive and geometric errors or inappropriate procedure. The f i t s well for some case. 1 39 d i s p l a c e m e n t f i e l d s c a n c a u s e l a r g e s p u r i o u s m e m b r a n e s t r e s s e s . 1 4 0 NORMALISED FAILURE LOAD F/Y Fig. 61 Shear Strength of Split Pipe 1 4 1 o C3 " —I 1 1 1 I 1 I I I I ! O.D 2.0 4.D 6.0 8.0 !0.0 LENGTH OF P I P E Fig.6.2 Va r i a t i on Of Pi pe S t i f f ne s s 1*2 0.0" NOTCHED 0.0" UN NOTCHED 8.0" NOTCHED 8.0" UNNOTCHED 6.0" NOTCHED •6.0" UN NOTCHED 4 1 1 1 1 1 1 I I l I 0.0 0.8 1.6 2.4 3.2 4.0 DIAMETER OF P I P E Fig.63Vario.tion Of Pipe Stiffness C3 1 4 3 O j — j i - -LU Q LO X CC o 10.0" NOTCHED 0.0"UN NOTCHED 80N0TCHE D 8.0"UN NOTCHED 6.0" NOTCHED 6.0"UNNOTCHED O.D —1 I I I I I I 0.9 1.6 2.4 3.2 DIAMETER OF P I P E 4.D Fi g. 6.4 Variat ion Of Maximum Deflection 144 225 NOTCHED 2.25"UNNOTCHED 2.00" NOTCHED 2.00" UN NOTCHED 1.00 NOTCHED 100" UN NOTCHED T T 2.3 4.11 6.0 Q.Q LENGTH OF P I P E JD.Q Fi<g.6.5 Variation Of Ductility 1 45 REFERENCES 1 Anderson, Arthur R., 'Introduction to Seismic Conceptual Design', Journal of the P.C.I., July/August 1972, pp-29-30. 2 Armer, G.S.T. and Kumar, S., 'Tests on Assemblies of Large Precast Concrete Panels', Precast Concrete, London, Vol.3, No.9, September, 1972, pp.541-546. 3 Atrek, Erdal, and Nilson, Arthur H., 'Non Linear Analysis of Cold-Formed Steel Shear Diaphragms', Journal of the Structural D i v i s i o n , ASCE, Vol.106, NO.ST3, March, 1980, pp.693-710. 4 Becker, J.M., Llorente, C. and Mueller, P., 'Seismic Response of Precast Concrete Walls', Earthquake Engineering and Structural Dynamics, Vol.8, 545-564 (1980). 5 Becker, J.M., Llorente, C , 'Seismic Design of Precast Concrete Buildings', Workshop on Earthquake-Resistant Reinforced Concrete Building Construction, July 1977, University of C a l i f o r n i a , Berkeley. 6 Burnett, E.F.P. and Rajendra, R.C.S., 'Influence of Joints in Panelized Structural Systems', Journal of the Structural D i v i s i o n , ASCE, Vol.98, No.ST9, September, 1972, pp.1943-1955. 7 Dawson, W.F., and Shemie, M.'Bolted Connections as a Substitute for on Site Welding and Wet Joints in Precast Concrete', Proceedings Canadian Structural Concrete Conference, Ottawa, Canada, 1977, pp.269-289. 8 Despeyroux, J., 'Structural Connexion Problems and the use of Special Materials in Precast Concrete Construction', Proceedings of a Symposium held at Church House London SW1 22-24 May, 1967, pp.99-118., Cement Concrete Association, London, 1968. 9 'Design Essentials in Earthquake Resistant Buildings', Edited by Architectural Institute of Japan, Elsevier Publishing Company. 1970. 10 Djabus, S.A., Chachava, T.N., Abashidze, G.G., Djish k a r i a n i , N.M. and Kemoklidze, G.S., 'Research on Seismic Resistance of Large-Panel Apartment Buildings', Sixth World Conference on Earthquake Engineering, New Delhi, 1977, pp.5-299-303. 11 Dowrick, D.J., 'Earthquake Resistant Design: A manual for engineers and a r c h i t e c t s ' , John Wiley & Sons. 1 46 12 Fazio, Paul, and Rizzo, Santi, 'Non Linear E l a s t i c Analysis of Panelized Shear Sandwich Walls', Journal of the Structural D i v i s i o n , ASCE, Vol.105, N0.ST6, June, 1979, pp.1187-1203. 13 F i n t e l , M., 'Performance of Precast Concrete Structures during Romanian Earthquakes of March 4, 1977', Journal P.C.I., Vol.22, No.2, March/April 1977, pp.10-15. 14 Franz, G., 'The Connexion of Precast Elements With Loops' , Design Philosophy and i t s Application to Precast Concrete Structures, Proceedings of a Symposium held at Church House, London, SW1, 22-24 May 1967, Cement Concrete Association, London, 1969. 15 Hawkins, N.M., 'State of Art Report on Seismic Resistance of Prestressed and Precast Concrete Structures-Part 2', Journal P.C.I. , Vol. 23, No. 1, Jan/Feb 1978, pp. 17-25-. 16 Hisada, T.'Large Size Structures Testing-Laboratory and Lateral Loading Test of a Five-Storied F u l l - S i z e Building Structure', Fourth World Conference on Earthquake Engineering, Santiago, Chile, 1969, V o l . I l l , pp.69-85. 17 Kahn, Lawrence F. and Hanson, Robert D., ' I n f i l l e d Walls for Earthquake Strengthening', Journal of the Structural D i v i s i o n , ASCE, Vol.98, No.ST5, May, 1972, pp.975-987. 18 Llorente, C , Becker, J.M., Roesset, J.M., 'The Effect Of Non-Linear-Inelastic Connection Behaviour on Precast Panelized Shear Walls', Symposium on Mathematical Modelling of Reinforced Concrete Structures, Committee 442, ACI, 1978. 19 Mathys, P.L. and Istvan, S.V., 'High Rise Panel Structures', Journal of the Structural D i v i s i o n , ASCE, Vol.98, NO.ST5, May, 1972, pp.975-987. 20 Mueller, P. and Becker, J.M., 'Seismic Characteristics of Composite Precast Walls', Third Canadian Conference on Earthquake Engineering, pp. 1169-1200. 21 'Multi-Tenant Warehouse Elk Grove V i l l a g e , I l l i n o i s , Journal P.C.I., Vol.26, No.4, July/Aug 1981, pp.122-126. 22 Muto, L., Ohmori, N., and Takahashi, T., 'A Study on Reinforced Concrete S l i t t e d Shear Walls for High-Rise Buildings', F i f t h World Conference on Earthquake Engineering, Rome, 1973, Vol.1, pp.1125-1138. 1 47 23 N e i l l e , Donald S., 'Behaviour of Headed Stud Connections for Precast Concrete Panels Under Monotonic and Cycled Shear Loading', Ph.D. Thesis, University of B r i t i s h Columbia, October 1977. 24 P a l l , Avtar S., Marsh, Cedric, and Fazio, Paul, ' F r i c t i o n Joints for Seismic Control of Large Panel Structures'Journal of the P.C.I., Vol.25, No.6, November/December 1980, pp.38-61 . 25 P a l l , A.S., Marsh, C , 'Seismic Response of Large Panel Structures using Limited S l i p Bolted Joints', Third Canadian Conference on Earthquake Engineering, pp.899-915. 26 Paulay, T. and Uzumeri, S.M., 'A C r i t i c a l Review of the Seismic Design Provisions for Ductile Shear Walls of the Canadian Code and Commentry', Canadian Journal of C i v i l Engineering, 2, 1975, pp.592-601. 27 Polyakov, S.V., et a l . , 'Investigation into Earthquake Resistance Large-Panel Buildings', Fourth World Conference on Earthquake Engineering, Santiago, Chile, 1969, Vol.1, pp. B-1 , 165-180. 28 P.C.I. Committee on Connection Details, 'Summary of Basic Information on Precast Connections', Journal of the P.C.I., Vol.15, No.1, Feb.1970, pp.67-78. 29 Shemie, M. 'Bolted Connections in Large Panel System Buildings', Journal of the P.C.I., Vol.18, No.1, Jan/Feb 1973, pp.27-33. 30 Shemie, M., 'Mechanical Joints in the Descon/Concordia Structural System', Proceedings Symposium on Panelized Structural Assemblies, 11-12 May 1972, Sir George Williams University, Montreal, Canada. 31 Spencer, Richard A. and N e i l l e , Donald S., 'Cyclic Tests of Welded Headed Stud Connections', Journal of the P.C.I., Vol.21, No.3, May-June 1976, pp.70-83. 32 Stafford Smith, B. and Lau, P.CM., 'A Method of Assesing the Static S t a b i l i t y of Panel Type Building', Proceedings of the Institute of C i v i l Engineers, London, Vol.53, June 1972 pp.77-86. 33 Stafford Smith, B. and Rahman, M.K.M., 'A Theoretical Study of the Sequence of Failure in Precast Panel Shear Walls', Proceedings of the I n s t i t u t i o n of C i v i l Engineers, London, Vol.56, September 1973, pp.581-592. 1 48 34 T h u r 1 i m a n n , B., ' F a t i g u e a nd S t a t i c S t r e n g t h o f S t u d S h e a r C o n n e c t o r s ' , J o u r n a l o f t h e A m e r i c a n C o n c r e t e I n s t i t u t e , J u n e 1959, p p . 1 2 8 7 - 1 3 0 2 . 35 V e n u t i , W.J., ' D i a p h r a g m S h e a r C o n n e c t o r s Between F l a n g e s o f P r e s t r e s s e d C o n c r e t e T-Beams', J o u r n a l o f t h e P . C . I . V o l . 1 5 , No.1, F e b . 1 9 7 0 , p p . 6 7 - 7 8 . 36 W a s t o n , V. and H i r s t , M.J.S., ' E x p e r i m e n t s f o r t h e D e s i g n o f a S y s t e m U s i n g L a r g e P r e c a s t C o n c r e t e P a n e l C o m p o n e n t s ' , The S t r u c t u r a l E n g i n e e r , ( L o n d o n ) , V o l . 5 0 , No.9, S e p t e m b e r 1972, p p . 3 4 5 - 3 5 4 . 37 Z e i n k i e w i c z , O.C., P a r e k h , C . J . , a n d T e p l y , B., 'Thr e e D i m e n s i o n a l A n a l y s i s o f B u i l d i n g s Composed o f F l o o r a n d W a l l P a n e l s ' , P r o c e e d i n g s o f t h e I n s t i t u t i o n o f C i v i l E n g i n e e r s , L o n d o n , V o l . 4 9 , J u l y 1971, p p . 3 1 9 - 3 3 2 . 

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