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Deformation of wood under load Siopongco, Joaquin Ordonez 1962-11-10

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D E F 0 R-: M A I I O N OF WOOD U N, D E R L O A D b y Joaquin Ordonez SIOPONG-CO, B. S • C . E., Mapua Institute of Technology, Philippines, 1953 A thesis submitted in partial fulfilment: of the requirements for the degree of MASTER- OF: APPLIED SCIENCE in the Department of CIVIL ENGINEERINGi We accept this thesis as conforming to the standard required from.candidates for the degree of Master of Applied Science Memhers of the Department of Ci v i l Engineering; THE UNIVERSITY OF BRITISH COLUMBIA August, 1962 In presenting t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the requirements f o r an advanced degree a t the U n i v e r s i t y o f B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. I f u r t h e r agree that permission f o r extensive copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head of my Department o r by h i s r e p r e s e n t a t i v e s . I t i s understood t h a t copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be allowed without•my w r i t t e n permission. JOAQUIN 0. S . I 0 P 0 N G C 0 Department of C I V I L ENGINEERING The U n i v e r s i t y of B r i t i s h Columbia, Vancouver 8 , Canada. Date August, 1962 • A B S T R A C T 7 ' ' C r e e p a n d r e c o v e r y t e s t s i n c o m p r e s s i o n p a r a l l e l t o t h e g r a i n w e r e c o n d u c t e d o n 2 i n . b y 2 i n . D o u g l a s - f i r - s p e c i m e n s 4- i n . l o n g a t f o u r d i f f e r e n t ^ l e v e l s o f m o i s t u r e . S p e c i m e n s w e r e l o a d e d i n s t a g e s up t o a p r e d e t e r m i n e d l o a d . I n s t a n t a n e o u s a x i a l a n d l a t e r a l d e f o r m a t i o n a s w e l l a s c r e e p m e a s u r e m e n t s w e r e t a k e n a t eac:h s t a g e . C r e e p w a s o b  s e r v e d ' o v e r p e r i o d s r a n g i n g f r o m f i v e m i n u t e s t o t w e n t y - f l v e h o u r s . S i m i l a r l y , r e c o v e r y was o b s e r v e d d u r i n g u n l o a d i n g a t ^ s u c c e s s i v e l y l o w e r s t r e s s l e v e l s . T h e r e a r e i n d i c a t i o n s t h a t ' : c r e e p a s w e l l a s n e g a t i v e c r e e p a n d n e g a t i v e r e c o v e r y w e r e m a i n l y d u e t o m o i s t u r e p r e s e n t i n t h e c e l l w a l l s . C r e e p , I n g e n e r a l , a p p e a r e d " t o b e m o r e m a r k e d i n t h e g r e e n s p e c i m e n s t h a n i n t h e i n t e r m e d i a t e • a n d a i r - d r y c o n  d i t i o n s . T h e o n l y o v e n - d r y s p e c i m e n s h o w e d l e s s c r e e p t h a n t h e a i r - d r y s p e c i m e n s . R e s u l t s a l s o s h o w t h a t t h e v a l u e s o f t h e c o e f f i c i e n t o f l a t e r a l d e f o r m a t i o n , yC{ =• - — - ; ( b o t h r a d i a l a n d t a n g e n t i a l ) , d u r i n g , t h e l o a d r i s e w e r e e n t i r e l y d i f f e r e n t f r o m t h o s e d u r i n g t h e p e r i o d o f c r e e p , i n d i c a t i n g t h a t t h e c o r r e s p o n d i n g d e f o r m a t i o n s w e r e e n t i r e l y d i f f e r e n t . Tcie y^/s f o r t h e c h a n g e I n l o a d w e r e a l w a y s h i g h e r t h a n t h o s e f o r the:; p e r i o d s o f c r e e p . A l l s p e c i m e n s t e s t e d s h o w e d a r e c o v e r y o f m o r e t h a n 50$ o f t h e l o n g i t u d i n a l c r e e p . T h i s i n d i c a t e s t h a t c r e e p i n w o p d i s made up o f t w o p a r t s , r e c o v e r a b l e a n d p e r m a n e n t c r e e p . ACKNOWLEDGMENTS The author gratefully acknowledges his indebtedness to his supervisor, Dr. A. Hrennikoff, for his expert guidance and help throughout the course of this study. The contri bution of his great knowledge and valuable time is greatly- appreciated. The author also wishes to express his gratitude to the members of the Department of C i v i l Engineering, University of British Columbia, particularly to Professor J. E. Muir., Head of the Department of Ci v i l Engineering. Appreciation is also due to Mr. K. G 3 . Rensom,.. Superin tendents of the Vancouver Laboratory, Forest Products Research Branch, Department of Forestry, Canada, for the use of the Laboratory's f a c i l i t i e s . The author Is also grateful to the External^ Aid Office, Government of Canada, and to the Forest Products Research Institute, Republic of the Philippines, for the Ccolomho Plan; Fellowship which made this study possible. August, 1962 Vancouver, British Columbia CONTENTS PAGE ABSTRACT . . . . . . . . . . . . . . . . . . . i i ACKNOWLEDGMENTS. . . i l l ILLUSTRATIONS. yr Part I. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . 1 II. DESCRIPTION OP TEST MATERIAL . . . . . . . . . 3 Species Used" . . . . . . . . . . . . . . . . 3 Type and Preparation of Test Specimens . . . 4 III. MOISTURE CONDITIONS AT TEST 6: Conditioning of the Specimens . 7 IV. EQUIPMENT USED 9 Testing Machine: 9 Stress-Strain Recorder 9 Lateral Deformation Apparatus 14 VJ. EXPERIMENTAL.,PROCEDURE 18 Measuring and Weighing?of Test Specimens. . . 18 Preparing the Specimen for.: Testing. . . . . . 18 Compression Tests of Control Specimens. . . . 19 Step-hy-Step Creep and Recovery Tests .... . 2 1 Repetitive Loading,. 24 VI. MOISTURE CONTENT AND SPECIFIC GRAVITY DETERMI NATION . . . . . . . . . 24 Moisture Content. - 25 Specific Gravity. . ... . . . . . .27 VII. RESULTS AND DISCUSSIONS 27 Creep and Recovery. . . . . . . .... . . . .27 Creep-Time Relationships. . . . . . . . . . . . . 30 Coefficient of Lateral Deformation. . . . . . 37 Step-wise Loading and Modulus of Elasticity . 39 Effect of Creep-Recovery Tests on the Subse quent: Stress-Deformation Relation . . 41 Permanent:, Set 43 Conclusions . . . . . . 43 LITERATURE CITED 45 ILLUSTRATIONS FIGURES • - • PAGE 1 . . ".. . • • .. • • • . ..... v . 5 2 . . . . • • • . . . 1 1 2 a . 1 2 3 . . . 1 6 4 . . . . . . . . . . . . . 26 5 - 1 0 . .31*36 11 - 1 7 . . . . 5 2 - 5 8 PHOTOGRAPHS 1 . 1 3 2 & 3 . . . . . . . . . 20 TABLES 1, 2 & 3 . . . 2 3 4 r 9 . . . . • 4 6 - 5 1 GRAPHS 1 - 9 . 5 9 - 6 7 Part I INTRODUCTION Wood, which was among the earliest materials to he used for construction, has long had an established place in the major field of structural engineering. Nowadays, through the wide application of results from fundamental and applied research, novel designs of large wooden structures are pos sible, making wood competitive with other materials such as steel and concrete. Glued, laminated wooden construction, for example, has already been recognized to be of primary Importance in this modern world of mechanization and automation. In the near future, prestressed or reinforced wooden members will likely join other engineered wood products for a more economical and satisfactory utilization of timber. It has become desirable, therefore, that studies be conducted on some of the basic aspects concerning the strain: behaviour of wood which take into account not only the effect of the. applied stress, but ln addition, the effect of time. This present investigation was carried out primarily to provide fundamental information on the creep of wood loaded in compression parallel to the grain at four levels of moisture content. It was also concerned with the effect of sustained loading at successively higher stress intensities on the modulus of elasticity, ultimate compressive strength and maximum deformation. 2 I n common w i t h many m a t e r i a l s , w o o d , w h e n s u b j e c t e d t o a c o n s t a n t f o r c e , e x h i b i t s a n i n c r e a s e i n d e f o r m a t i o n f o l  l o w i n g a n i n i t i a l i n s t a n t a n e o u s s t r a i n . T h i s s u b s e q u e n t i n c r e a s e l n d e f o r m a t i o n , c a l l e d c r e e p o r p l a s t i c f l o w , i s t i m e d e p e n d e n t a n d b e h a v e s i n o n e o f t w o w a y s . T h e c r e e p may t a k e p l a c e e i t h e r a t a c o n t i n u o u s l y d e c r e a s i n g r a t e u n t i l i t a p p r o a c h e s a n u l t i m a t e o r l i m i t i n g v a l u e ; o r , i t may s h o w g r a d u a l l y d i m i n i s h i n g r a t e a t f i r s t , t h e n a c o n s  t a n t r a t e a n d f i n a l l y a n i n c r e a s i n g r a t e w h i c h e v e n t u a l l y l e a d s t o f a i l u r e . P r e v i o u s i n v e s t i g a t i o n s e l s e w h e r e h a v e s h o w n t h a t w o o d , u n d e r a l l t y p e s o f l o a d i n g , e x h i b i t s c r e e p e v e n w h e n t h e s t r e s s i s w e l l b e l o w t h e s t a n d a r d p r o p o r t i o n a l l i m i t ( 1 , 3 , 4 , 5 , 6 , 7 , 8 } 1 . T e s t s a t t h e U . S . F o r e s t P r o d u c t s L a b o r a t o r y a s r e p o r t e d b y Wood (8) h a v e s h o w n t h a t D o u g l a s - f i r a n d w h i t e o a k b o t h e x h i b i t n o t i c e a b l e c r e e p w h e n s u b j e c t e d t o t e n s i o n a n d c o m p r e s s i o n p a r a l l e l t o t h e g r a i n a t s t r e s s e s a s l o w a s 1500 p s i . W o o d a l s o r e p o r t e d t h a t t h e r e i s a n i n d i c a t i o n t h a t c r e e p i n t e n s i o n a n d c o m p r e s s i o n i s a p p r o  x i m a t e l y p r o p o r t i o n a l t o s t r e s s . D i e t z (3) i n h i s i n v e s t i g a t i o n o f t h e c r e e p b e h a v i o u r o f D o u g l a s - f i r f o u n d t h a t f o r c o m p r e s s i v e s t r e s s e s b e l o w t h e p r o p o r t i o n a l l i m i t , t h e c r e e p i s v e r y l o w . T h e A u s t r a l i a n F o r e s t P r o d u c t s L a b o r a t o r y (1) r e p o r t e d 1 N u m b e r s i n p a r e n t h e s i s r e f e r t o l i t e r a t u r e c i t e d . 3 o b s e r v i n g i n c r e a s e s i n s t r a i n f r o m 20 t o 1 4 0 p e r c e n t i n g r e e n m o u n t a i n a s h s p e c i m e n s s u b j e c t e d t o c o m p r e s s i o n f o r a l m o s t t h r e e y e a r s a t s t r e s s e s r a n g i n g f r o m 10 t o 35 p e r c e n t o f t h e s h o r t t i m e s t r e n g t h . P a r t I I D E S C R I P T I O N OF T E S T M A T E R I A L S p e c i e s U s e d D o u g l a s - f i r ( P s e u d o t s u g a roenzlesll), a s p e c i e s o f p r i m e i m p o r t a n c e i n w o r l d m a r k e t s f o r s t r u c t u r a l g r a d e s o f l u m b e r , was t h e s p e c i e s c h o s e n f o r t h i s p a r t i c u l a r e x p e r i m e n t . A s r e p o r t e d i n F . P . L . T e c h n i c a l N o t e ? N o . 3, " S t r e n g t h a n d R e l a t e d P r o p e r t i e s o f Woods G r o w n I n C a n a d a " , D o u g l a s - f i r s h o w s t h e f o l l o w i n g a v e r a g e v a l u e s i n c o m p r e s s i o n p a r a l  l e l t o t h e g r a i n s M o i s t u r e C o n t e n t 2 _ 4 1 $ 1 2 $ N o m i n a l S p e c i f i c G r a v i t y ^ 0 . 4 5 0 . 4 9 S t r e s s a t P r o p o r t i o n a l L i m i t 2 8 1 0 p s i , 4 8 3 0 p s i . M a x i m u m C r u s h i n g S t r e s s 3 6 1 0 p s i . . 7 2 3 0 p s i . M o d u l u s o f E l a s t i c i t y 1,670,000 p s i . 1,950,000 p s i . S o u r c e a n d S e l e c t i o n o f t h e E x p e r i m e n t a l M a t e r i a l M a t e r i a l u t i l i z e d i n t h i s w o r k was o b t a i n e d f r o m a f l a t - s a w n p l a n k s e l e c t e d f r o m a s t o c k o f D o u g l a s - f i r o n h a n d a t t h e C i v i l E n g i n e e r i n g L a b o r a t o r y , U n i v e r s i t y o f B r i t i s h C o l u m b i a . B a s e d o n w e i g h t w h e n o v e n - d r y . B a s e d o n v o l u m e a t t e s t a n d w e i g h t w h e n o v e n - d r y . 4 In order to simplify the interpretation of the results, l i t was considered desirable to use test pieces free of defects including knots, as straight grained as possible, and with sufficiently flat growth rings. When selected, the plank was in an air-seasoned condition registering a moisture content of about 12%-with an electric moisture meter. Type and Preparation of Test Specimens The specimens used in these experiments were nominally two-by-two inches in cross-section and four inches in length parallel to the grain (See Fig. 1 ) . The plank was surfaced on both flat grain faces to a nominal thickness of 2-| inches, the grain direction was determined, and sticks 2 i-inch wide were ripped parallel to the grain with growth rings as nearly as possible paral l e l and perpendicular to the end edges of the sticks. These were cross-cut into 5-inch lengths to produce end-matched blocks for the test specimens and their controls, and into 4-inch lengths for moisture content sampling. The indivi dual pieces were reduced to final size only after they have already attained a moisture content very near the desired final condition.' In the final processing of the test specimens and their controls, particular care was taken not only to Improve further the orientation of the annual rings so as to make them essentially at right angles to a pair of faces, but T A i V G £ V T I AL 1 - T E S T SPECIMEN/ also to make three sides of the blocks t r u l y and mutually perpendicular to each other. Each specimen was designated by a c a p i t a l l e t t e r which indicated the moisture condition under which i t was to be tested; air-dry condition was designated by the l e t t e r "A", intermediate moisture condition by "M!1, green condition by "G", and oven-dry condition by "0". For the controls, the l e t t e r "C" was simply added. Thus, CA-1-6 Indicates the control specimen i n the air-dry condition. Part I II MOISTURE CONDITIONS AT TEST Creep and recovery tests i n compression p a r a l l e l to the grain were conducted at four d i f f e r e n t l e v e l s of mois ture?^, namelys 1. Air-Dry Condition - i n which the moisture content of the specimens at test was i n equilibrium-with the atmos phere of the tes t i n g laboratory. The specimens were gene r a l l y very close to 10$ moisture content. 2. Intermediate Condition - i n which the moisture con-, tent was above 12$ butt below the f i b r e saturation point of the species which i n t h i s case Is about 24$ (2). Nominal moisture content f o r t h i s condition was chosen to be 20%", 3. Green:Condition - In which the moisture content was above the f i b r e saturation point, the moisture content ranging. from 4 7 $ to 6 6 $ . 4 . Oven-Dry Condition - in which the moisture content was very close to zero. Conditioning of the Specimens A l l test specimens were stored in temperature-and- humidity controlled rooms or. chambers that would bring: them to the desired final moisture content under which they were t'o be tested. Those assigned to tests in the air-dry condition were stored exposed to the atmospheric conditions of the testing room until they reached constant weight. These specimens came to equilibrium at moisture contents ranging from: 9 . 3 $ to 1 0 . 2 $ . Those to be tested in the intermediate conditions were conditioned and stored in a chamber over a saturated solution of sodium sulphate. The chamber was maintained at a tempera ture of 75?F. At this temperature the relative vapor pres sure above the salt solution was such as to result in mois ture conditions that would give a nominal equilibrium mois ture content ln the blocks of 2 0 $ . Those to be tested In the green conditions were stored , ln a controlled-humidity-temperature room. To facilitate the conditioning of these green specimens, they were first- submerged in water under a vacuum for about three days. Those to be tested in the oven-dry condition were conditioned in a thermostatically controlled electric oven h e a t e d a t 2 1 2 ° F a n d d r i e d u n t i l n o c h a n g e i n w e i g h t was o b s e r v e d f o r a p e r i o d o f t w e n t y - f o u r h o u r s . D u r i n g t h e c o n d i t i o n i n g p e r i o d , t h e s p e c i m e n s w e r e w e i g h e d p e r i o d i c a l l y , f i r s t a t l o n g i n t e r v a l s a n d f i n a l l y , w h e n t h e y h a d v e r y n e a r l y a t t a i n e d t h e i r e q u i l i b r i u m m o i s  t u r e c o n t e n t s , m o r e f r e q u e n t l y . T h e w e i g h i n g - w a s c o n t i n u e d u n t i l m o s t o f t h e s p e c i m e n s i n e a c h c o n d i t i o n h a d m a i n t a i n e d a n a l m o s t c o n s t a n t w e i g h t i n d i c a t i n g ; , t h a t t h e y h a d a t t a i n e d t h e r e q u i r e d e q u i l i b r i u m m o i s t u r e c o n t e n t : . P e r i o d i c a l l y , a m o i s t u r e s a m p l e a b o u t a n i n c h t h i c h was t a k e n f r o m t h e c e n t r e o f t h e m o i s t u r e s a m p l e b l o c k s a n d t h e m o i s t u r e c o n  t e n t , a n d i t s d i s t r i b u t i o n t h r o u g h o u t t h e c r o s s - s e c t i o n , d e t e r m i n e d b y t h e o v e n - d r y m e t h o d . ( S e e M o i s t u r e C o n t e n t - a n d S p e c i f i c G r a v i t y D e t e r m i n a t i o n o n p a g e 2 4 ) . W h i l e e v e r y a t t e m p t was made t o b r i n g t h e a i r - d r y , ; i n t e r m e d i a t e a n d g r e e n s p e c i m e n s t o a u n i f o r m m o i s t u r e c o n  t e n t o f 1 0 $ , 2 0 $ , a n d 6 0 $ , r e s p e c t i v e l y , b e f o r e t e s t i n g , I t was i n e v i t a b l e t h a t some s p e c i m e n s e x h i b i t e d a m o i s t u r e c o n t e n t s l i g h t l y h i g h e r o r l o w e r t h a n t h e d e s i r e d l e v e l . H o w e v e r , f o r t h e f i r s t t w o c o n d i t i o n s , i t was d e e m e d i m p e  r a t i v e t h a t n o t w o s p e c i m e n s s h o u l d h a v e a d i f f e r e n c e i n m o i s t u r e e o f m o r e t h a n 1 0 $ o f t h e n o m i n a l v a l u e , i . e . , 1 $ a n d 2 $ , r e s p e c t i v e l y , o t h e r w i s e t h e t e s t was d i s c a r d e d . F o r t h e g r e e n s p e c i m e n s , s u c h l i m i t a t i o n was n o t n e c e s s a r y s i n c e m o s t o f t h e s t r e n g t h p r o p e r t i e s o f w o o d a r e I n f l u e n c e d b y m o i s t u r e c o n t e n t o n l y i n t h e r a n g e b e l o w t h e 9 f i b r e s a t u r a t i o n p o i n t . T h e s p e c i m e n s w e r e k e p t u n d e r t h e s e c o n d i t i o n s u n t i l r e m o v e d o n e a t a t i m e f o r t e s t i n g . P a r t I V EQUIPMENT USED T e s t i n g M a c h i n e A l l t h e t e s t i n g was p e r f o r m e d o n a B a l w i n T a t e - E m e r y T e s t i n g M a c h i n e w i t h a maximum c a p a c i t y o f f o u r - h u n d r e d - t h o u s a n d p o u n d s a n d h a v i n g t h r e e r a n g e s o f l o a d . O n l y t w o r a n g e s , t h e 8 0 , 0 0 0 - l b . r a n g e , g r a d u a t e d a t 1 0 0 - l b . i n t e r v a l s , a n d t h e 1 6 , 0 0 0 - l b . r a n g e , g r a d u a t e d a t 2 0 - l b . i n t e r v a l s , w e r e u s e d i n t h e s e e x p e r i m e n t s . A l o a d m a i n t a i n e r , w h i c h i s a n a c c e s s o r y o f t h e t e s t i n g m a c h i n e , was u t i l i z e d i n h o l d i n g t h e l o a d c o n s t a n t o v e r a p e r i o d o f t i m e i n o r d e r t h a t c r e e p o r r e c o v e r y c o u l d b e d e v e l o p e d . W i t h t h e u s e o f t h e l o a d m a i n t a i n e r , n o f l u c t u a  t i o n s i n t h e l o a d h a v e b e e n o b s e r v e d e v e n w h e n h e l d o v e r n i g h t . A s t o p - w a t c h was u s e d t o m e a s u r e t h e t i m e i n t e r v a l s w h i l e o b s e r v i n g c r e e p o r r e c o v e r y . S t r e s s - S t r a i n R e c o r d e r A n a u t o g r a p h i c r e c o r d e r , t h e M i c r o f o r m e r S t r e s s - S t r a i n R e c o r d e r , was u s e d t o p r o v i d e a r e c o r d o f l o a d v e r s u s s p e c i  men d e f o r m a t i o n m e a s u r e d o v e r a g a u g e l e n g t h o f t w o i n c h e s . T h i s a p p a r a t u s c o n s i s t s e s s e n t i a l l y o f t w o p a r t s , t h e c o m -10 pressometer which is attached to the specimen and the micro- former type recording equipment which produced autographic load-strain records of compression tests made parallel to the grain. The recording' equipment consists pf a drum around which is wound a graph paper and a pen attached at the end of a push-rod which is in turn geared mechanically to the load indicating pointer of the testing machine. There are two coordinate axes in the graph; the load coordinate which is parallel to the axis of rotation of the drum and the strain: coordinate which runs around the circumference of the drum. The load is marked by the pen which moves parallel to the axis of the drum while the drum rotates in proportion to specimen:deformation. The compressometer (Figs. 2 and 2 a ) includes a pair of: gauge rings which are attached to the test specimen at a gauge length of two inches and a measuring assembly which measures the average values of displacement occurring between the gauge rings as the specimen is loaded. Each of the gauge rings is clamped to the test block by a pair of screws at points P and P^ . The measuring assembly, which is also shown In Photo graph 1, includes a heavy base supporting: a vertical frame work, two pairs of measuring arms and a microformer measu ring unit. Each pair of measuring arms, upper arms and lower arms, pivots on a common axis A or.A-,. Stable contact 4 CORE. COIL UPPER ARM UPPER 6AUGE RIVG F R A M E A , - LOWER ARM SPECIMEN 1 r-dlSl " r rp L O W E R GAUGE R lkG 3 B, I i W W F19-2-DIAGRAM OF C0MPRE5S0METER 13 P h o t o g r a p h 1 M e a s u r i n g assembly of eompressometer 14: between the measuring arms and the gauge rings at points Bi or is maintained by the balance weights W. The microformer measuring unit consisting of a coil unit and a movable core Is fixed to the lower arm. The core, with a spring underneath, is forced to keep Ih contact with the upper arm at point Cr; When the test specimen shortens under the action of the load, the distance between the gauge points P and Pj decreases:: and the upper and lower arms rotate about their respective axes A and A^ causing their rear ends to move farther from each other. This results in the movement of the core relative to the c o i l . This motion of the core ln relation to the--coll unit actuates the rotation of the drum in the recording equip ment proportional to the deformation of the gauge length of the specimen. Two of the three available strain magnification settings of the Stress-Strain Recorder were used in recording the longitudinal deformation occurring within the gauge length of two inches. These are the "intermediate" and the "High" which correspond to strain scales of 1~1000 micro-inches per inch and l'-*-5Q0 micro-Inches per inch, respectively. Lateral Deformation Apparatus To measure lateral deformation, creep or strain reco very, either in the radial or tangential directions, a special apparatus was devised. This apparatus was designed 153 and patterned a f t e r the one developed and used by Dr. A. Hrennlkoff of the Department of C i v i l Engineering of the University of B r i t i s h Columbia f o r measuring the l a t e r a l s t r a i n and creep of a concrete c y l i n d r i c a l specimen. As shown In F i g . 3> i t consists of two channel-shaped s t e e l c o l l a r s A joined by two bent iso - e l a s t i c ^ " s t r i p s which are fastened to the c o l l a r s by means of small screws. The square ri n g formed by the c o l l a r s and" bent s t r i p s i s clamped on the test specimens by two large thumb:, screws B passing through the mid-points of the c o l l a r s . The i s o - e l a s t i c springs form the s e n s i t i v e elements which bend as the specimen undergoes d i s t o r t i o n i n the l a t e r a l dimension when i t i s subjected to a longitudinal compressive force. The bending strains l n the i s o - e l a s t i c springs are sensed by two Budd SR-4, Type C3-141-B e l e c t r i c a l resistance s t r a i n gauges glued on the inner and the outer faces of both springs. A l l Inside gauges C and separately a l l ouside gauges D are connected i n series and attached to the active and.compensating terminals of a Baldwin SR-4 Type L S t r a i n Indicator whose readings are nearly proportional to the l a t e r a l strains l n the specimen. With th i s arrangement, the inside gauges were also made active, but stressed d i f f e r e n t l y from the outside ones. The indicator would then show the difference of the two strains which are of the opposite 4 Iso - e l a s t i c i s an a l l o y of iron, n i c k e l and chromium possessing p a r t i c u l a r l y f i n e e l a s t i c properties. . 5 - L A T E R A L DEFORMATION APPARATUS ATTACHED TO THE RADIAL SIDES TO M E A S U R E TANGENTIAL DEFORMATION 17 signs,,thus increasing the sensitivity of the apparatus. In order to be able to make simultaneous observations on the lateral strain, creep or recovery on both radial and tangential faces of the specimen, two apparatuses of this kind were made and used. It was also necessary to use a Baldwin switching^and balancing unit to be able to read several gauges while using only one strain Indicator. The design of the lateral deformation apparatus con sists mainly of( determining the cross-sectional dimensions and geometry of the iso-elastic springs. Based on a useful range of strain of 3,000 micro-inches per inch, the spring was designed so that its stress will not exceed its elastic limit of 50 kips per square inch. In addition, a minimum force of about a third of a pound, was provided for as the in i t i a l force necessary to hold the apparatus In the speci men by friction alone. When calibrated, the two apparatuses showed a sensi tivity of 3.18 and 3.36 which means that a strain reading of 1 micro-inch per inch in the indicator corresponds to a strain of 3.18 or 3.36 micro-inches per inch on the test specimen. Calibration of the apparatus was done by means of a 2-inch diameter cold rolled steel cylinder the lateral strains of which are known from strain gauges mounted directly on the cylinder. 1 8 Part V EXPERIMENTAL PROCEDURE Measuring and Weighing of Test Specimens Immediately "before testing, each specimen was weighed to an accuracy of 0.01 gram and its cross^sectional dimen sion and length measured to the nearest 0.01 inch. After weighing and measuring, i t was carefully wrapped and sealed completely with Saran Wrap, a polyvinyl plastic film, in order to prevent any increase or decrease in the moisture content of the specimen while the testing was in progress. Immediately after each creep-recovery test, the specimen was weighed again to determine whether or not .there was any change in moisture during the test. When a variation in weight of more than 1$ was found, the test was cancelled. The change in weight before and after testing of the test specimens reported in this work was found to have a maximum value of only 0.3$ which is an indication of the effectiveness of wrapping the specimens with Saran; Wrap. Preparing the Specimen for Testing The proper attachment to the test specimen of the four rings (two lateral deformation rings and the two com- pressometer rings) was.accomplished with the aid of four set-up posts, which, together with the rings, formed a rigid frame (See Photograph 2 ) . One lateral deformation ring is clamped on the tangential sides of the test block 19 to measure strain in the radial direction and the other on the radial faces to measure tangential distortion. Centre to centre distance of these two rings is five-eights of an inch and they are placed equidistant from the upper and lower compressometer rings. The posts are removed when the rings have been securely attached in their respective posi tions . Photograph 2 shows, the four rings and the set-up posts forming a rigid frame before attachment to the specimen. Photograph 3 shows the rings attached to the specimen. Compression Tests of Control Specimens Initially, one end-matched control specimen was taken at random from each condition and tested in compression parallel to the grain according to standard procedures, except that the special compressometer was used to measure a deformation over a 2-lnch gauge length. The specimen was subjected to progressive loading until failure, the rate of loading being maintained at a constant speed of: approximately 0.012 inch per minute as per ASTM specifications. This gives the rate of loading from the following formulas n = Z x / where ni = speed of the movable head of the machine in inches per minute. Z = rate of fibre strain per inch of fibre length length of compression specimen The value commonly used for Z is 0.003, therefore, tn = 0.012 inch per minute. P h o t o g r a p h 2 L a t e r a l d e f o r m a t i o n a n d c o m p r e s s o m e t e r r i n g s r i g i d l y c o n n e c t e d w i t h f o u r s e t - u p p o s t s b e f o r e a t t a c h m e n t t o a s p e c i m e n . P h o t o g r a p h 3 L a t e r a l d e f o r m a t i o n a n d c o m p r e s s o m e t e r r i n g s s h o w n i n t h e i r p r o p e r p o s i t i o n s o n t h e s p e c i m e n . 21 While the recorder made possible the continuous and automatic recording of the load-axial strain graph, at least two persons were needed for the test, one reading the load and the other reading and recording the lateral strains from the strain indicator. The lateral strains were then plotted against load. From these sets of load-deformation- curves, the two Poisson's ratios, -^^/z a n d ^t-t * w e r e cal culated. The Poisson's ratio or ^ i c r represents the numerical value of the ratio of the strain along the radial or tangential direction to that along the longitudinal direc tion due to a compressive stress parallel to the grain. The results of these tests established the ultimate crushing strength of each of the three conditions of testing and permitted a"selection of the various fixed stress-levels to which the other specimens were tp-be rlpaded in; a step wise manner. Step-by-Step Creep and Recovery Tests In this type of test the specimen was subjected to compression parallel to the grain In successive steps at the desired various stress levels. A very rapid rate of loading; was used so that no creep would come into play during the application of the load. The time of loading from one stress-level to the next, higher one was about five seconds. At every designated level of stress, the load was sustained for a desired period of time to record the - I 22 creep strain along the three perpendicular axes, after which the load was raised to the next step and at successively higher stress levels according to the loading schedule given in Tables 1, 2 and 3. Several load levels, chosem arbi trarily, were used, ranging from 13 to 91 per cent of the control's maximum load for the air-dry specimens, from 24 to 96 per cent for the intermediate conditions and from 23 to 81 per cent for the green specimens. As in the testing of the control specimens, the load axial-strain.relation was recorded automatically, and lateral strains, both in the radial and tangential directions, were read from the strain indicator and recorded throughout the duration of the test. Ih addition, time intervals were noted on the load-axial strain graph while simultaneous readings were made for any change of deformation in the lateral direc tions. Creep was observed and recorded under a sustained loading for a minimum period of five minutes in some stress levels and a maximum of twenty-five hours at other levels of load. Measurements of creep were made every minute for the fi r s t five or ten minutes, every two or three minutes for the next ten or twenty minutes, and then as the creep rate became smaller, at convenient random time increments. After stressing to a selected maximum stress-level had been completed, the specimen was unloaded in a similar step-by-step manner (See Tables 1, 2 and 3 for unloading schedule). Table 1 - SCHEDULE OF STEP-BY-STEP LOADING-UNLOADING TESTS . ."' . (AIR-DRY CONDITION) Load L e v e l L 0 A D I. . N G U 1 Y L 0 A D I N. a k i p s 4 6 12 lo" 18 20 - 22 24 28 20 16 12 8 4 0 Per cent of max. l o a d 13 26 39, 52 59 65 72 78 91 65 52 39 26 13 0 of c o n t r o l s Specimen Tine d u r a t i o n of s u s t a i n e d l o a d a t each I Load l e v e l i n minutes A-l-5 5 5. 5 20 . 225 5 5 5 20 330 A-l-7 5 15 15 20 15 5 5 5 15 180 A-l-4 5 5 5 5 1510 1500 5 5 5 15 3095 A-l-3(a) ••(b) 5 30 25 • 25 30 135 5 15 25 35 5 15 35 195 (°) 5 15 15 15 15 5 5 5 5 5 10 135 Table 2 - SCHEDULE OF: STEP-BY-STEP LOADING.-UNLOADING TESTS • ' (INTERMEDIATE CONDITION) Load L e v e l L 0 A D [ N G U N 1 . 0 A D I N G k i p s 4 8 10 12 15 16 8 4 0 Per cent of max. l o a d 24 48 60 72 89 96 48 24 0 of c o n t r o l s * Specimen e Pirne d u r a t i o n of s u s t a i n e d l o a d a t each l o a d ] Level i n minutes Mrl-2 5 60 60 5 5 215 M - l - 9 5 5 5 75 5 10 145 M-l-3 5 20 30 10 5 15 155 M-l-10 5 5 5 1040 10 20 1250 M-l-4(a) 5 5 30 10 75 (b) 5 5 5 60 5 10 150 M-l-7(a) 5 5 30 5 10 70 (b) 5 5 5 30 5 10 115 Table 3 - SCHEDULE OF STEP-BY-STEP LOADING-UNLOADIN&.:TESTS (GREEN CONDITION) Load L e v e l L 0 A D I N ( U N L O A D I N" 4 k i p s 4 . 8 10 12 14 8 4 0 Per cent of max. l o a d 23 46 58 69 81 46 23 0 of c o n t r o l s Specimen Time d u r a t i o n of s u s t a Lned l o a d a t each loa< a l e v e l i n m i n u t e s G-l-9 5 10 10 5 10 75 0-1-5 5 5 962 20 1025 0-1-3 r 5 20 20 10 5 5 90 GE-1-6 5 15 30 10 5 15 135 G-l-7(a) 5- 25 25 10 95 (b) 5 25 25 25 15 5 10 150 (a) 1st. c y c l e of r e p e t i t i v e l o a d i n g . (b) 2nd. c y c l e of r e p e t i t i v e l o a d i n g . (c) 3rd. c y c l e of r e p e t i t i v e l o a d i n g . 24 Longitudinal and l a t e r a l s t r a i n recovery - the creep on.the unloading part of the cycle - were observed and recor ded following the same technique used i n creep observation. F i n a l l y , the same specimen was tested i n a continuous operation without stops to f a i l u r e at a machine speed of •"'"0.012 inch per minute. Each te s t was continued u n t i l the load f e l l well below the maximum. This f i n a l test was done only a f t e r there was no further d i s c e r n i b l e recovery taking place i n the specimen i n i t s unloaded state a f t e r a considerable length of time which was i n a l l cases equal or more than the tes t i n g time. Repetitive Loading In t h i s test, the specimen was loaded as i n the previous step-by-step creep and recovery t e s t s . Then a f t e r being- un loaded, the specimen was loaded again i n a s i m i l a r step-wise fashion. For each succeeding loading cycle the selected maximum s t r e s s - l e v e l was made higher than that of the pre vious one. Specimens tested i n t h i s ty.peoof r e p e t i t i v e loading were not.reloaded u n t i l s t r a i n recovery, both axial ' and l a t e r a l , was v i r t u a l l y complete. A recovery period of at l e a s t two hours at the unloaded state was allowed between, loading cycles. As before, each specimen was f i n a l l y loaded to f a i l u r e . Part VU MOISTURE CONTENT AND SPECIFIC GRAVITY DETERMINATION The moisture content and s p e c i f i c gravity of each te s t 2 5 s p e c i m e n w e r e d e t e r m i n e d f r o m a s m a l l s a m p l e t a k e n a d j a c e n t t o t h e p o i n t o f f a i l u r e . M o i s t u r e C o n t e n t T h e m o i s t u r e c o n t e n t was d e t e r m i n e d b y t h e o v e n - d r y m e t h o d i n t h e f o l l o w i n g m a n n e r s (1) A f t e r e a c h f i n a l t e s t , a n d a f t e r w e i g h i n g t h e s p e c i  m e n , a m o i s t u r e s a m p l e a b o u t a n i n c h i n t h i c k n e s s was t a k e n a n d c u t i n t o s e c t i o n s a s s h o w n i n F i g . 4. M o i s t u r e d e t e r m i  n a t i o n s ' w e r e made f o r t h e c o r e a n d e a c h o f t h e s h e l l s s e p a  r a t e l y i n o r d e r t o d e t e r m i n e t h e m o i s t u r e d i s t r i b u t i o n a t t h e c r o s s - s e c t i o n o f t h e b l o c k . (.2) I m m e d i a t e l y a f t e r s a w i n g , a l l l o o s e s p l i n t e r s w e r e r e m o v e d a n d e a c h s e c t i o n was w e i g h e d t o t h e n e a r e s t 0.01 g r a m b y means o f a M e t t l e r t y p e b a l a n c e g r a d u a t e d t o t h e n e a r e s t 0. 10 g r a m / b u t w h i c h c o u l d b e r e a d b y i n t e r p o l a t i o n t o t h e n e a r e s t 0.01 g r a m . (3) T h e m a t e r i a l was t h e n p u t i n t o a t h e r m o s t a t i c a l l y c o n t r o l l e d e l e c t r i c o v e n h e a t e d a t 212° F a n d d r i e d u n t i l t h e r e was n o v a r i a t i o n i n w e i g h t f o r a p e r i o d o f t w e n t y - f o u r ho u r s . (4) U p o n a t t a i n i n g t h i s c o n d i t i o n o f c o n s t a n t w e i g h t , 1. e . , w h e n a l l t h e m o i s t u r e h a d b e e n e v a p o r a t e d , t h e m a t e r i a l was a g a i n c a r e f u l l y w e i g h e d . (5) T h e l o s s i n w e i g h t e x p r e s s e d i n p e r c e n t o f t h e o v e n - d r y w e i g h t i n d i c a t e s t h e m o i s t u r e c o n t e n t o f t h e s p e c i  men f r o m w h i c h t h e s a m p l e was c u t . T h e v a r i a t i o n i n m o i s t u r e c o n t e n t b e t w e e n t h e c o r e a n d s h e l l s was l i m i t e d t o 0.1 %, 2* Fig-4 - M E T H O D O F ' C U T T I N G M O I S T U R E S A M P L E F O R D E T E R M I N A T I O N O F S H E L L A N D C O R E M O I S T U R E D I S T R I B U T I O N 27 S p e c i f i c G r a v i t y The s p e c i f i c g r a v i t y f o r each specimen was c a l c u l a t e d t o the n e a r e s t 0.001 on the oven-dry weight, volume a t t e s t b a s i s . P a r t V I I RESULTS AND DISCUSSIONS Creep and Recovery Creep and recovery data, b o t h a x i a l and l a t e r a l , o b t a i n e d from t e s t s i n compression p a r a l l e l to the g r a i n at the f o u r moisture content c o n d i t i o n s i n v e s t i g a t e d a re p r e s e n t e d i n Tables 4 and 5. In g e n e r a l , creep, i n the l o n g i t u d i n a l and l a t e r a l d i r e c  t i o n s , was found to be more marked i n the green specimens than l n e i t h e r the Intermediate or a i r - d r y c o n d i t i o n . The only oven-dry specimen showed l e s s e r creep than the a i r - d r y ones. Appare n t l y , creep i n wood i s due mainly to the moisture prese n t i n the c e l l w a l l s . Upon a p p l i c a t i o n of the l o a d , water i n the w a l l s i s compressed so as to c a r r y p a r t of the l o a d . While the l o a d i s h e l d constant, the moisture i s f o r c e d i n t o the c e l l c a v i t i e s and the p r e s s u r e i s r e l i e v e d . The load, p r e v i o u s l y c a r r i e d by the compressed water i s t r a n s  f e r r e d to the f i b r o u s m a t e r i a l , thus causing f u r t h e r deforma t i o n . The reason t h a t the oven-dry specimen s t i l l showed some creep i s probably due to the f a c t t h a t a l l the moisture was not e x p e l l e d . During the rise in load, the specimen undergoes an increase in the lateral directions. When the load is sus tained for a period of time, lateral creep occurs usually in the sense of bulging. In some cases, however, the lateral creep occurred in the opposite direction. This unusual phenomenon, in which the lateral dimension tends to contract instead of expanding further under a sustained longitudinal compressive stress, and which we will now call negative creep, has been observed to be more marked and predominant In the green specimens than in the speci mens of intermediate moisture content. Por the latter, only one, usually the upper level, in three stress levels at which creep was observed snowed negative creep while in the green condition almost a l l of the stress levels showed negative creep. Similar phenomena were also observed in the unloading part of the test. When the stress is reduced or released, a decrease in the lateral directions occurs, and a further; contraction usually * develops during the period of sustained load. At tne low levels of stress in the intermediate and green conditions, however, an expansion in the lateral dimensions was noted during recovery following unloading. Again we will term tnis as negative recovery. As with negative creep, there was a preponderance of negative reco very observed in the green specimens. However, not a l l the stress levels under which negative 29 creep was r e c o r d e d e x h i b i t e d a s i m i l a r n e g a t i v e r e c o v e r y . Por example, i n Specimen M-l-2, there was a c o n s i s t e n t n e g a t i v e creep both i n the r a d i a l and t a n g e n t i a l d i r e c t i o n s b ut no n e g a t i v e recovery e i t h e r r a d i a l l y o r t a n g e n t i a l l y was r e c o r d e d . T h i s was a l s o found to be t r u e w i t h S p e c i  men &-1-3 ( F i g . 15;), but i n the t a n g e n t i a l d i r e c t i o n o n l y . On tne other hand, the creep and r e c o v e r y i n the two l a t e r a l d i r e c t i o n s of Specimen u-1-6 ( F i g . 16) were found to be b o t h n e g a t i v e . Such i s the case, too, w i t h Specimens M-l-4 and G—1-3 i n t h e i r r a d i a l d i r e c t i o n s . S i n c e n e i t h e r n e g a t i v e creep nor r e c o v e r y was observed i n the a i r - d r y specimens t e s t e d and because such behaviour was found to have o c c u r r e d more i n the green than i n the i n t e r m e d i a t e c o n d i t i o n , i t becomes obvious t h a t the mois t u r e content of the specimens had something to do w i t h the n e g a t i v e c r e e p i n g and r e c o v e r y . I t seems t h a t d u r i n g the r a p i d a p p l i c a t i o n of the l o a d , p r e s s u r e i n the water w i t h i n the c e l l s t r u c t u r e b u i l d s up c a u s i n g l a t e r a l expansion i n a d d i t i o n t o the normal d i s t o r t i o n of the wood substance. When the l o a d i s s u s t a i n e d , some moisture f i n d s I t s way i n t o a d j o i n i n g c a v i t i e s . The water p r e s s u r e i n the c e l l w a l l s i s thus reduced, r e s u l t i n g i n the l a t e r a l c o n t r a c t i o n , of the f i b r e s . Hence, n e g a t i v e creep i s developed. Negative recov e r y can be e x p l a i n e d i n the same way. A f t e r r e d u c t i o n or removal of the l o a d , s u c t i o n i s developed and the mois t u r e i s a t t r a c t e d back to the c e l l w a l l s , thus c a u s i n g 30 l a t e r a l expansion d u r i n g the p e r i o d of s u s t a i n e d l o a d . Creep-Time R e l a t i o n s h i p s F o r each I n d i v i d u a l t e s t specimen, a x i a l creep v a l u e s , expressed as percentages of the t o t a l e l a s t i c s t r a i n , from zero l o a d t o the s t r e s s l e v e l of tne creep, were p l o t t e d a g a i n s t time a t every creep l e v e l and smooth curve l i n e s were f i t t e d v i s u a l l y . The s t r e s s l e v e l s are expressed as percentages of the specimen's a c t u a l maximum crushing, s t r e s s . By way of e x p l a n a t i o n , the specimen's a c t u a l maximum c r u s h i n g s t r e s s , as used here, i s the u l t i m a t e s t r e n g t h o b t a i n e d from the s t a t i c compression p a r a l l e l t o the g r a i n t e s t performed a f t e r tne specimen had been s u b j e c  t e d t o the step-by-step creep and r e c o v e r y t e s t s as d e s c r i b e d e a r l i e r . Due to the n a t u r a l v a r i a b i l i t y of wood, and due to tne e f f e c t of the f i r s t type of' t e s t i n g , the a c t u a l s t r e s s l e v e l s , expressed as the percentages of tne u l t i m a t e com p r e s s i v e s t r e n g t h or each specimen, d i f f e r e d somewhat from the assumed s t r e s s l e v e l s which were based on the compressive s t r e n g t h of the c o n t r o l specimens. T y p i c a l creep curves showing the r e l a t i o n s h i p of c r e e p - p e r c e n t a g e - o f - e l a s t l c - s t r a i n and time, under v a r i o u s s t r e s s e s , are shown i n F i g s , b and 6 f o r the a i r - d r y specimens, i n F i g s . 3' and © f o r the i n t e r m e d i a t e c o n d i t i o n , and i n F i g s . 9 and 10 f o r the green specimens. Each s e t of curves i s the r e s u l t of a t e s t w i t h an i n d i v i d u a l specimen. 31 TIME. \w • ± L + J f c y : i ^ i M E •WtH PAftALLEL. I p . ; M I N U T E S . j-f-i-fH-j i r TO GRAlhZ. . L .L i J .L - L L , ' ! • : ! i I 1 i i . L L i t : :U±: i. I iL,.j ! -L. RELATlf OV-SHIP.I A t DI F B E R E V . T L ST .RES5 LEVELS AlRfDRY SPECIMEN/ U/: CPMPRESSIOV :]:!:HIT:I^:L;: J - r - : -L j - j—^—j-)•  : STRE55 ! L E V E L S ARtjlL'JSHOWW L A S P I ; R C E V'fTAGES iii • iii. i • : ; > ~ ! i • i ' ' i i i i i i i . i ' , i ' ; -i OF MS A C T U A L CRO SHIN'S C R E E P , STRAW: AS S T R A l U P ; TO £ACM PARTICL _4- L. II iv. ci i. _ 4-4-1- ! P E R C E t f T A $ T K E V 6 T H . ' " L.I.±jJ_ L iSTiR-ESSl ILlEME Lit"- x^±H±L: AL: ELASTIC • 32 - U U J LL" H - H - & mi -bg J to U U -</>H _ _l_L_i._ - U - -J±r-U-I j_ I . I i - ! • - - V II i l l J_ . ..!_. „LJ. ; o... : j-LL_1.4j._1 M M j. ' • : z l . i r p 1 .]_•_. J J 4 J1.LJ u J M ' 1 . 1 i - | _ M - . J J _ _ . L . i _ 4 .tl-LL 1 . 1 r r JJ-L , J _ ! .4 . 1 1 1 • 4- -! L i X l l T r r T r 1 _!_]_: . L l l i : ! -J.. LI.LLJJ J.J TT I n i T i j T " i;;r]-M-rp"j 1 J __.•••- 4 J — J "I 1 I ; j !' ;t::;riDL L . L . L . . 1 ! ! i" : 4 W 1J. .I ' J _ J M - U . J - I H I ' T ^ J - ''"XIT'J T:H~£i:f 1.! I I 1 ! T L.l- 4 444 } I i M : 1 i 1—M ' ' 1 4 4 r r n : m J . _ _ J _ J J _ N4- X t E I r l — H - J - h - H j - i - u - LL"LLJ___L ) __!_L ' tr-i-f- as 1"TT 1 i"i -1 T T 4 J ! M . i L f!- J M f±] E l I I -|4-' ' 44 4-1- •0- TIT I ! i Tl " i J J m 1 m . J . . "! L"U"i m" t 1 -4- i M 4 M M -ri-i-i -]~n -1 TJ n : :63 t t J J J J . -!-M -j-j.4 j-IOL I 1 J _1. IP c z q . T d<_:&: A X I A j ; T I M E ; \u • I M ; T .. -: ,---.-J_].-_- *ii MUTES LlCR_:E iP4TiXlM!E^BZU"AXI.CWS.UIP. ; AT !J._.I. _i !_,..; I__Q__: • RAW: M^Tj JT . I . U LI ! M j i t - -H-- !~i 4 T J T •ARE : SWQV/is/ . CRU..\-UwG „ i : ^ ^ f l : p 4 i ^ r E A : i : w . 'STRAW : UP TO ; L E V E L S ; : A \ R - _ > R V rsPEcrHiEk : :w . 1 - 1. i i 1 • • ' EP-B_^5JIE-_1 44-i-!-J3_.J4j44a-i--!-LL j ! ! M ' L ^ , 1 j ; { 1 1 i 4 4 4 4 n 4 - r r j JJWFf?tRtyX-d SIREi>S ij___A^ _n_v_a: i i J j , : " rr 1 i j j 1 i ; ST.REIS/GTW.. m.- 4." X l X J - p l t • • j j _ |_t. G F I I T S . : J A S J : : P E ——. JJ_] U < M M ! 1 , ALLEL M M ! ' ' A C T . U A t:! f : T O T A L , : E : L A S T I C i t :L.:E"VE.L4: : |; i 4 I tl i . 'M M I i 1 33 T i p : ns::84 IAYI^:LT.cREtrp-^IWE;:. RELAT POM(kgE5SlCW PAKA1 I E L TO 1 gRAltv\ iOf/SHIP. : AT DI FFEj RE^Tf '•1-STREIS3 r: V S R E C I .STEP^&Y- r i T T . L . . . J . . LOADING::: FJSTR - t - r t C E N T A G E S or EiSS ; "X.EV.E L S : ARE ITS i A C j r u A L e e b S M i t f c .0--!- P S T R A I N ST R/jui\/ UP! TO . EACH.: ; PARTICULAR TOTAL] ' -Li. .L> SJTRET/vSTH. •f{t r — 5 E L A S T I C FT !" L L i I S T R E S S | L E V E L . i . i i . ; I L . L . . KlG. 10: - AXIAL ; CREEP-TIME- RELAT LEV A R C . * C R _ } E P TIME ; lh/ E:LSl<5REEh/: S R E C I M E p : 1IV1 ! SHOWN/ WIIVG: ; A S . . : PE.RC STREK/S m STB A M UP ! TO l_l 1: sTRAI^; ; A S : ; PER .: E A C H i r • I ; • , i I : .Mi:|/UT y s : i O V S ^ f l P • JVTA&ES : rEtvTAGE. j ?ARTIC "l "i -; U J - A T . DIFFERS* COMPRESSION • iH-l-H-, i QtxirrdTA]:. ULAP:: 'STRESS r! i i ! • T . S T R E S S 1 : - - U - H ' i l l J - • P A R A U L F i l ^IJILEVS^.:.!: ! i i ! j ! i I ! ^ q T i ^ ' L i i t i__i =" ^ i 1 ! _t~r : ELASTIC V E L . . . 1 1 Tt- -j Tt i l _ i J ± — 1 i 37 At about 90$ stress level i t appears that there is a rapid increase in creep, f i r s t at a decreasing rate, then at a constant rate and finally again at an increasing rate. Although none of the specimens was allowed to f a i l under a constant load, other investigators (8) have pointed outtthat the increase in the rate of creep Is a sign of imminent failure. Continuous deformation at a diminishing rate, until an almost constant value is ultimately reached, Is characteris tic of the creep curves for stress levels up to about 70$. These curves are relatively flatter than those of the 70 - 77$ stress levels. Within the stress levels and time range used in this investigation, these curves indicate that creep proceeds rapidly for the f i r s t few minutes after which the rate gradually diminishes with increasing time. Coefficient of Lateral Deformation A specimen subjected to a compressive force undergoes deformation not only In the direction of the applied load but also in the lateral direction. Within the elastic limit of. the material, the ratio of these deformations, lateral to longitudinal, is commonly known as the Poisson's ratio. In wood, this elastic property is obtained from standard tests made at a uniform rate of loading. Similar ratios are given in Tables 6 and 7. They are herein referred to as the coefficients of lateral deforma- tion, yCf ~ ' These are of two kinds, namely, the r a t i o of s t r a i n increments f o r the change In load and the r a t i o of strains during the period of creep or recovery. In order to di s t i n g u i s h them from the usual Poisson's r a t i o s , ^(A^ and y^fLj- $ we designate the c o e f f i c i e n t s of r a d i a l and tangential deformation by ^^{^ a n d ^C^- * r e s P e c = t i v e l y . Typical yl^ diagrams are presented i n F i g s . 11 and 12 f o r the air-dry.specimens, i n F i g s . 13 and 14 f o r the i n t e r  mediate condition and i n Fi g s . 15 and 16 f o r the green condi t i o n . F i g . 17 i s that of the oven-dry specimen. The values of the c o e f f i c i e n t of l a t e r a l deformation, both r a d i a l and tangential, during the period of creep are en t i r e l y d i f f e r e n t from those during the load r i s e , i n d i c a  t i n g that the corresponding deformations are e n t i r e l y d i f f e  rent. In a l l the specimens tested, the yC^3 f o r the period of creep showed consistently lower values than those f o r the change l n load. At almost a l l stress l e v e l s , the c o e f f i c i e n t of tangen t i a l deformation exhibited a higher value than i t s r a d i a l counterpart. This i s probably due to the medullary rays running r a d i a l l y i n the wood which r e s t r i c t s i t s deformation i n the r a d i a l d i r e c t i o n . During the loading part of the cycle, some of the sum -/-yO{r have been observed to be greater than one, indic a  t i n g that the material i n a way opens up. On the other hand, the negative sum^^y^ indicates a reduction i n volume of the material. Whenever fe a s i b l e , the /C{s during the period of creep were calculated separately f o r d i f f e r e n t parts of time i n t e r - v a l s . These values appear to become smaller with increase i n time f o r the intermediate condition while the reverse i s true f o r the air-dry condition. Step-wise Loading and Modulus of E l a s t i c i t y I l l u s t r a t e d i n Graphs 1, 2, §, 4, and 5 are t y p i c a l graphs traced automatically by the stress-strain.recorder during the step-wise creep-recovery tests i n compression p a r a l l e l to the grain. At ieach l e v e l of load, short ver t i c a l l i n e s were drawn on the horizontal portions of the.. graphs. These represent time increments i n minutes during;, which creep or recovery, a x i a l or l a t e r a l , was recorded. Whenever there was measurable creep or recovery, marking was done every minute f o r the f i r s t f i v e or ten minutes, every two or three minutes f o r the next ten or twenty minutes, and so on, the time inte r v a l s gradually increasing; thereafter. Due to the rapid rate at which the load was raised, the load a x i a l deformation r e l a t i o n s h i p was, f o r a l l prac t i c a l purposes, l i n e a r on each load Increment. Such a l i n e a r behaviour was observed to exist i n some specimens even.up to stress regions beyond the standard proportional l i m i t of the material, where It would normally plo t as a 40 curved l i n e under the ordinary rate; of t e s t i n g . Graphs 2 and 4, with load l e v e l s up to 95 and 92 per cent of the specimen's actual strength,respectively, w i l l serve to i l l u s t r a t e the foregoing statement. Obviously., the curved portion, of a s t r e s s - s t r a i n graph as o r d i n a r i l y obtained by the conventional testing method, i s mainly due to creep that i s taking place within the dura t i o n of the:.-loading time. In general, however, the slopes of the straight l i n e s between two consecutive loads f o r each graph are not of equal magnitude. As one goes from one i n t e r v a l to the next higher i n t e r v a l , the slopes have a tendency to become smaller, though not consistently so. Consequently, because the modulus of e l a s t i c i t y i s d i r e c t l y proportional to the slope, a s i m i l a r l y decreasing Young's modulus i s evident from the figures i n Table 6. In. the air-dry specimens, the decrease i n the modulus of e l a s t i c i t y was of the order of 2 to 6 per cent with the excep t i o n of Specimen A-1T-3 where a 12$ reduction was noted from the f i r s t - to the second-step i n t e r v a l . Generally, the per centage decrease was greater i n the intermediate condition and s l i g h t l y higher f o r the green specimens, the former,having a maximum reduction of 21$ and the l a t t e r a maximum of 26$. The sai d l i n e a r i t y i n the graphs i s also evident during unloading, although to a lesser degree, especially during the l a s t unloading step where a pronounced c u r v i l i n e a r graph has been observed In. a l l the intermediate and green specimens. 41 T h i s c u r v i l i n e a r c h a r a c t e r i s t i c c o u l d b e a t t r i b u t e d t o t h e m o i s t u r e i n t h e ; w o o d . U p o n r e l e a s e o f t h e l o a d , s u c t i o n i s d e v e l o p e d c a u s i n g t e n s i o n i n t h e w a t e r a t f i r s t a n d f i n a l l y t h e w a t e r t h a t h a d b e e n f o r c e d o u t o f t h e c e l l w a l l s d u r i n g t h e p e r i o d o f c r e e p , i s r e v e r t e d . T h i s a c c o u n t s t o t h e c u r v a t u r e o f t h e u n l o a d i n g c u r v e . I t w i l l a l s o b e o b s e r v e d f r o m t h e same g r a i p h s t h a t i n t h e f o r m a t i o n o f t h e h y s t e r e s i s l o o p , t h e s t r a i n f o r a g i v e n l o a d i n c r e m e n t i s g e n e r a l l y g r e a t e r . u p o n r e l e a s i n g t h e s t r e s s t h a n u p o n a p p l y i n g i t . O r , p u t t i n g i t i n . a n o t h e r w a y , t h e m o d u l u s o f e l a s t i c i t y i s s m a l l e r o n r e l e a s e o f a l o a d t h a n o n i t s a p p l i c a t i o n . T h i s seems t o i n d i c a t e t h a t u p o n d e c r e a s e o r r e m o v a l o f t h e , c o m p r e s s i v e s t r e s s , t h e r e i s , i n a d d i t i o n t o t h e e l a s t i c s t r a i n , a n i m m e d i a t e r e c o v e r y o f a p o r t i o n o f t h e c r e e p . T h i s was f o u n d t o b e t r u e i n a l l t h e s p e c i m e n s t e s t e d i n t h e i n t e r m e d i a t e a n d g r e e n c o n d i t i o n s w h i l e t h e a i r - d r y s p e c i m e n s d i d n o t s h o w s u c h a c o n s i s t e n t t r e n d . E f f e c t o f C r e e p - R e c o v e r y T e s t s o n t h e S u b s e q u e n t S t r e s s - D e f o r m a t i o n R e l a t i o n G r a p h s 6, 7, 8 a n d 9 a r e e x a m p l e s o f t y p i c a l g r a p h s • s h o w i n g t h e l o a d - a x i a l a n d l o a d - l a t e r a l s t r a i n r e l a t i o n s h i p s o b t a i n e d f r o m a c o m p r e s s i o n p a r a l l e l t o t h e g r a i n t e s t d o n e a t a u n i f o r m t e s t i n g r a t e o f a b o u t 0.012 i n c h p e r m i n u t e . A s i n t h e o t h e r g r a p h s , t h e l o a d - a x i a l c u r v e was a u t o m a t i c a l l y r e c o r d e d w h i l e t h e t w o o t h e r g r a p h s ( r a d i a l a n d t a n g e n t i a l ) w e r e p l o t t e d f r o m e x p e r i m e n t a l d a t a o b t a i n e d t h r o u g h t h e s t r a i n i n d i c a t o r . 4 2 W i t h , t h e e x c e p t i o n o f G r a p h 6, w h i c h i s t h a t o f a c o n  t r o l : , s p e c i m e n , t h e s e g r a p h s a r e a l l f r o m s p e c i m e n s t h a t , h a v e b e e n p r e v i o u s l y s u b j e c t e d t o t h e c r e e p a n d r e c o v e r y t e s t s . I t w i l l b e n o t i c e d f r o m t h e l a s t t w o g r a p h s , w h i c h a r e t h o s e o f t h e i n t e r m e d i a t e a n d g r e e n c o n d i t i o n s , r e s p e c t i v e l y , t h a t t h e l o a d - a x i a l c u r v e s s h o w a d e v i a t i o n f r o m s t r a i g h t n e s s a l m o s t f r o m t h e o r i g i n , a l t h o u g h t h e c u r v a t u r e i s h o t v e r y p r o n o u n c e d . T h i s c h a r a c t e r i s t i c i s p r e s e n t i n a l l t h e c u r v e s o f t h e i n t e r m e d i a t e a n d g r e e n s p e c i m e n s . G r a p h 7 , o n t h e o t h e r h a n d , i s t y p i c a l f o r t h e a i r - d r y s p e c i m e n s , w i t h t h e e x c e p t i o n o f S p e c i m e n A - l - 5 , w h i c h a l s o e x h i b i t e d a n o n - p r o p o r t i o n a l s t r e s s - s t r a i n r e l a t i o n s h i p s i m i l a r t o t h a t o f e i t h e r G r a p h 8 o r 9. A l l t h e c u r v e s , h o w e v e r , s h o w e d a d e f i n i t e p e a k t h a t i n d i c a t e d maximum l o a d f r o m w h i c h t h e maximum s t r e s s a n d s t r a i n v a l u e s a s g i v e n i n T a b l e : 8 w e r e o b t a i n e d . A l s o i n c l u d e d i n T a b l e 8 a r e t h e m o i s t u r e c o n t e n t a n d s p e c i f i c g r a v i t y o f e a c h s p e c i m e n , a n d t h e m o d u l u s o f e l a s  t i c i t y a n d P o i s s o n ' s r a t i o s o f t h e c o n t r o l s . F r o m t h i s t a b l e a c o m p a r i s o n o f t h e p r o p e r t i e s o f t h e i n d i v i d u a l s p e c i m e n s w i t h . t h o s e o f t h e i r c o r r e s p o n d i n g c o n t r o l s c a n b e m a d e . A l l t h e a i r - d r y s p e c i m e n s t e s t e d h a v e s h o w n h i g h e r u l t i m a t e c o m  p r e s s i v e s t r e n g t h t h a n t h e i r c o n t r o l s , t h e i n c r e a s e b e i n g o f t h e o r d e r o f 4 t o 8 p e r c e n t . L i k e w i s e , f o r t h e i n t e r m e d i a t e c o n d i t i o n , a l l b u t t w o s h o w e d g r e a t e r s t r e n g t h t h a n t h e i r c o n t r o l s , t h e p e r c e n t a g e o f i n c r e a s e v a r y i n g f r o m 5 t o 16. F o r t h e g r e e n s p e c i m e n s , t h e o p p o s i t e r e s u l t was o b t a i n e d 43 t h a t I s , t h e c o n t r o l , s h o w e d h i g h e r c r u s h i n g s t r e s s . A r e  d u c t i o n o f a b o u t 20 p e r c e n t was n o t e d i n a l l b u t o n e o f t h e g r e e n s p e c i m e n s . A l l t h e s p e c i m e n s t e s t e d a t t h e t h r e e m o i s t u r e c o n d i t i o n s ( a i r - d r y , i n t e r m e d i a t e a n d g r e e n ) e x h i b i t e d s t r a i n s a t m a x i  mum l o a d c o n s i s t e n t l y g r e a t e r t h a n t h o s e o f t h e i r r e s p e c t i v e c o n t r o l s . P e r m a n e n t S e t A x i a l a n d l a t e r a l ( r a d i a l a n d t a n g e n t i a l ) p e r m a n e n t s e t a n d s t r a i n r e c o v e r y e x p r e s s e d a s p e r c e n t a g e o f t h e a x i a l c r e e p a r e t a b u l a t e d i n T a b l e 9 . E a c h o f t h e r e s i d u a l s t r a i n v a l u e s was t a k e n a t the^ t i m e w h e n n o m o r e m e a s u r a b l e r e c o v e r y , was t a k i n g p l a c e . F r o m t h e t a b l e i t , w i l l r e a d i l y b e o b s e r v e d t h a t , i n a l l c a s e s , m o r e t h a n h a l f o f t h e a x i a l c r e e p t h a t h a d t a k e n p l a c e h a d b e e n u l t i m a t e l y r e c o v e r e d . H e n c e , c r e e p o f w o o d c o u l d t h e n b e c l a s s i f i e d i n t o t w o k i n d s , n a m e l y , r e c o v e r a b l e c r e e p w h i c h o t h e r w o r k e r s h a v e c o n s i d e r e d a s a n e l a s t i c a f t e r - e f f e c t o r d e l a y e d e l a s t i c i t y , a n d p e r m a n e n t c r e e p , o r p l a s t i c d e  f o r m a t i o n . R e c o v e r a b l e c r e e p i n t h e l a t e r a l d i r e c t i o n was n o t d e t e r m i n e d b e c a u s e o f t h e a c c i d e n t a l d i s t u r b a n c e o f t h e l a t e r a l d e f o r m a t i o n a p p a r a t u s a t t h e e n d o f . t h e t e s t . C o n c l u s i o n s T h e m o r e i m p o r t a n t c o n c l u s i o n s i n t h i s i n v e s t i g a t i o n a r e a s f o l l o w s : A{-~r?—: ^ 1. Creep, b o t h l o n g i t u d i n a l and l a t e r a l , i n t h e g r e e n specimens was, i n g e n e r a l , more marked t h a n i n e i t h e r t h e i n t e r m e d i a t e o r a i r - d r y c o n d i t i o n . The oven-dry specimen showed c r e e p r e s p o n s e l e s s t h a n t h a t of t h e a i r - d r y s p e c i  mens. Creep, t h e r e f o r e , c o u l d he a t t r i b u t e d m a i n l y t o t h e p r e s e n c e o f m o i s t u r e i n t h e c e l l w a l l s . 2 . N e g a t i v e c r e e p and n e g a t i v e r e c o v e r y i n t h e . l a t e r a l . d i r e c t i o n s o b s e r v e d i n t h e i n t e r m e d i a t e and g r e e n c o n d i t i o n s were due t o m o i s t u r e p r e s e n t i n t h e c e l l w a l l s . 3. V a l u e s of t h e c o e f f i c i e n t of l a t e r a l d e f o r m a t i o n , ( b o t h r a d i a l and t a n g e n t i a l ) , d u r i n g t h e l o a d r i s e a r e e n t i r e l y d i f f e r e n t from t h o s e d u r i n g t h e p e r i o d of c r e e p , i n d i c a t i n g t h a t t h e c o r r e s p o n d i n g deforma t i o n s a r e e n t i r e l y d i f f e r e n t " . T h e i n t h e t a n g e n t i a l d i r e c t i o n i s u s u a l l y g r e a t e r t h a n t h e yCf- I n t h e r a d i a l d i r e c t i o n . T h i s I s p r o b a b l y due t o t h e m e d u l l a r y r a y s r u n  n i n g r a d i a l l y i n the wood w h i c h somehow r e s t r i c t . i t s deforma t i o n i n t h a t d i r e c t i o n . 4 . D e c r e a s i n g m o d u l i of e l a s t i c i t y have been o b s e r v e d d u r i n g l o a d i n g a t s u c c e s s i v e l y h i g h e r s t r e s s l e v e l s . 5. S t r e s s - s t r a i n c u r v e s from f i n a l t e s t s o f t h e i n t e r m e  d i a t e and g r e e n specimens were f o u n d t o be- c u r v i l i n e a r from t h e b e g i n n i n g o f l o a d i n g , a l t h o u g h t h e c u r v a t u r e was n o t v e r y pronounced. 6 . More t h a n h a l f of t h e l o n g i t u d i n a l c r e e p t h a t had d e v e l o p e d was u l t i m a t e l y r e c o v e r e d i n a l l t h e specimens t e s t e d . 45 LITERATURE CITED 1. Australian Forest Products Laboratory. 1955 - 1956. Annual Report. CS3R0, Division of Forest Products, Australia. 2. Canadian wood - their properties and uses. 1951. Forestry Branch, Forest Products Laboratory Division, Ottawa. 3. D'ietz, A. Cf. H. 1949. Short-time creep tests on Douglas-fir. Proceedings Forest Products Research Society, 3: 352-360. 4. Khukhryanshii, P. N. 1953. Relaxation and creep of natural and densifled wood under compression. Akademia nauk SSSR Trudy lntituta lesa, 9 ; 337-346:. (Translated by E. Feigl, CSJRO Translation No. 4802, i960). 5. King, E. GB. Jr:; 1957. Creep and other strain behavior of: wood in tension parallel to the grain. Forest Productss Journal, 7 (10); 324-334. 6. , . 1958. The strain behavior of wood in tension parallel to the grain. Forest:ProductscJournal, 8 (11): 330-334. 7.. Kings ton, R. S. T. and L. D. Armstrong. 1951. G:reep in: initially green wooden beams. Reprint from Australian Journal of Applied Science, 2 (2): 306-325. 8. Wood, L. W. 1947. Behavior of wood under loading.. Engineering News Record, 139 (24): 108-111. 50 Table 8 - VALUES FROM FINAL STATIC TESTS IN COMPRESSION PARALLEL TO GRAIN FOLLOWING CREEP-RECOVERY TESTS. Specimen M o i s t u r e Content i%) S p e c i f l o G r a v i t y Max. S t r e s s ( p s i . ) Max. S t r a i n (mlcro- in./in J Modulus of E l a s t i  c i t y (lOOOpsj) Poisson's R a t i o 0 - 1 - 1 oven-dry 0 . 4 7 2 1L400 12200 C A - 1 - 6 * 9 . 6 0 .497 7300 6000 1890 0 . 3 7 2 0 . 4 0 2 A - l - 5 9 . 6 0 . 504 7860 7300 A - l - 7 1 0 . 2 0 .541 7760 13,050 A - l - 4 9 . 3 0 . 4 9 2 7750 6700 A - l - 3 9 . 6 0 . 4 9 2 7600 6200 C M - 1 - 1 * 1 9 . 9 0 .491 4190 4400 1610 0 . 2 1 0 0 .596 M - l - 2 20o8 0 . 4 9 1 4400 4800 M - l - 9 2 0 . 3 0 .518 3720 4720 M - l - 3 2 1 . 8 0 . 4 9 0 4400 5500 M-l - 1 0 2 0 . 0 0 .541 4850 7900 • M - l - 4 2 0 . 0 0 . 5 0 0 4180 4650 CG - 1 - 1 0 * 6 3 . 0 0 .547 4100 3850 2000 0 . 3 4 2 0 .651 G - l - 9 4 6 . 9 0 . 5 4 5 3290 4300 G - l - 5 6 0 . 5 0 .498 3280 6240 G - l - 3 6 5 . 5 0 . 5 0 4 3320 4250 G - l - 6 6 2 . 1 0 . 4 9 9 3250 6600 G - l - 7 5 7 . 4 0 . 547 3900 4850 C o n t r o l specimens-were not su b j e o t e d to creep-recovery t e s t s . 5 1 T a b l e 9- PERMANENT SET AND STRAIN RECOVERY OF DOUGLAS-FIR TESTED FOR CREEP - P e r m a n e n t S e s t S t r a i n Recovery . Specimen R a d i a l T a n g e n t i a l L o n g i t u d i n a l Percentage of (micro-inches per lnoh) A x i a l Creep 0 - 1 - 1 A - 1 - 5 A - 1 - 7 A - 1 - 4 A - l - 3 ( a ) (b) (c) M - 1 - 2 M - 1 - 9 M - 1 - 3 M - l - 1 0 M - l - 4 ( a ) (b) M - l - 7 ( a ) (b) G - 1 - 9 G - 1 - 5 G - 1 - 3 0 . - 1 - 6 0 - 1 - 7 ( a ) (b) 0 4 8 4 8 « * # - 2 7 0 - 2 7 1 3 8 - 3 2 - 3 2 * 3 4 - 3 0 6 0 - 2 2 - 6 7 ft 1 7 7 7 9 1 « 1 0 2 3 2 • - 1 6 - 1 2 7 2 9 4 3 4 0 - 6 - 1 9 « - 3 5 - 2 0 - 2 9 « 6 0 2 7 0 3 0 0 3 7 0 2 7 0 0 4 0 7 0 0 8 0 7 5 0 4 9 0 1 4 4 0 1 0 0 1 6 0 5 0 8 0 2 2 0 8 0 0 1 7 5 4 6 0 3 0 1 8 0 5 1 . 8 7 0 . 4 5 3 c * • : . . 5 6 . 5 1 0 0 . 0 8 7 . 3 5 5 o 5 8 3 . 5 7 7 . 7 7 9 o 9 6 4 . 6 6 0 . 6 8 1 o 9 7 8 o 2 9 0 . 6 8 2 . 1 7 6 o 7 8 9 o 4 8 7 o O 8 9 » 3 8 8 . 8 i * No va l u e s r e c o r d e d due to a c c i d e n t a l d i s t u r b a n c e of the l a t e r a l deformation apparatus. (a) Values of 1 s t . c y c l e . (b) Values of 2nd. c y c l e . (c) Values of 3 r d . c y c l e . TAMGEMTl A L F i ' 9 . 1 - T E S T S P E C I M E N Y CORE O C UPPER ARM COIL -YrL - - ^ L - U P P E R GAUGE RIV6 FRAME A f SPECIMEN LOWER ARM LH 4 _ 5 ^ + 5 B, i i L O W E R GAUGE RING r J I BASE t W Fig.2-DIAGRAM OF COMPRESSOMETER t 6 A Section. X~X Fig .3 - LATERAL DEFORMATION APPARATUS ATTACHED TO THE RADIAL SIDES TO M E A S U R E TAN/GEN/TIAL DEFORMATION/ 2° Fig. 4 - METHOD OF CUTTING MOISTURE SAMPLE FOR DETERMINATION/ OF SHELL AN/D CORE MOISTURE DISTRIBUTION H— • -• i — i 1 I 1 | $ - - T ft 11J - - - -i • 1 j 1 L L L I . r I Q. - 1 1 I Mi Til t£. j j .'i -i i . . . . 1 I P I 1 -• J ,0 - bis * -J J i i 1 -- | - ! ?l i: I E —, S P -1 1 A s 1 i 1 P \ — A x IA 'S c BEE E RE .ATIOVS AT JIFF E R E WT S RESS L E T KE:L l • T t T I T L 1 l S P E I C I W E V i r T i i i u i .LLQJ.J.. j._ •LLJ.L. 1 .A.I.R- >RY 1 KU__QO_M P R I I L P A R A L l LLfJ.JI -E.L 1 1 T.i j _ _i. i . L-ftsJ_ 1 1 M J J 1 J _ T O T S l i l t l l . ; . . — \ \ L T T T I I T T l i TT E I J J - J i-1_ . 1. 1 i.1.1.1 A jaws | T } 5W [ff sm 3AT5_ 1 1 1 JElvG" _P 1 . R c E i T o F C 71 J T .1 --ORVJ5 -• i f ' T r ) ' * : t ±b 3 IP i: I :i C TfiWfF 4 • _ J A S -t i 1 RC &W_TAG-E f| pjOT-A L "T j % P ,s: 1 ! 1 El\ • i £E;L t i_ -00 1 I- . 1 . . I q - t h 1 j * 7 I -ill 1 7 1 1" — 1 1 ! - j _ ] . 1 ... -_1—! 1 — 1 — 1 - 1 I l i b ! t i - -1 -- r r 7 ______ | ] -• 1 - - — * i I •5 i ... -» ^ H 1 ~ DJ 1 u 1 - J- -jU 1 - 1 - V • -j - — * - - -- /- -- - - - 1 l _ 1 % — -- - 1 1 II - — -1 1 -i>7. 0- 8 3 Iff. 1 A i r JO. us: 1 • 20 ME WE: REDAT :n: U U TTT"T _. '1 ! J.TJ11 1 I STREI m isjri:RA.);iv_4^ A X E : MltyOXE.S: ICWSWIP. 1.1 :dszip' - 30. ^CiTlOAE E A C H LLPARTtCULAR - L U SRECI T U t - r . SHOWN* -.LU-.U-i i t t t t C R O S f c j l l vs: 8'ER_ .1 T I. S T R E S S M S X T P E ' R E i ! 1 s:tRr«S-TLWt :; S T R E S S * ELASTIC 1 1 ft . - | I j -! 1 - - - -•_ - -1 — ; -i ! 1 I, -- f _LL_ - 1 i j_LJJ. . - - - " r i i ' i 1 - -! 1 1 i I -J_ - - 1 1 i i i 1 i — - -7 - l * 0 1 Mr •* -:< -i* V) _'oJ_ -A 0 -U -iii —«x* y --I -U. 1 0 •3 0 i i i i 1 i. - r \ > - | - \ r - R 1 • -1 - r i - m --1 9- 1 • • 1 j > 1 ... j i e . 1..: j r T _ - : i i • II -ziyxp ri 1 — i i: M :i l •F i" 1--v- I E__ M 5 -I 1 — - r :c A 1 L 1 RE E I I j tTIMf li ATTC /; > P :i P A a : E r. E E i: $ ER i CO i i i i l TVTE l I • M i l l 11 1 . J T \k i LJ....T R E S S LVE.LS T i l l P A R m GREE SPEC M E M i I i GQM-1 E .1 1 1 :i 1 i I'. 1_ T f r i 1 SSTOls i l IT LE. : I D lAlAtl SXEEr I J X LST.EP ..1, 1 T r n j i i 1 E l i i T I J _ i 1 R¥ t SSL J_ i l_ V E L S LAKE. S I . W R A S T - i n n i TT r J - \ r L 1 •i' i i i r i- J . T t¥ Tit i f ff- S f / U J _ i n c I i .i i F r T 1 T M T T RT k 1 1 i 1 1 1 I • r 1 ...LL i rREEP i i i J :. 1. T S J R Avrs/ :CEh/_TASE . [ A L T LAST;I.S_ 1 J.-JJJI II I l l J M i I M M ±E&g.UG.lb.LAR M 1 .1 1 1 ! 1 • >  1 STR.E3i§LTL"Ey.E.L, - 4,0 J J . . 1 1 —- | 1 - f ' V 4 1 — - f - i ~ 1 1 —i | 1 | — - - *-t— — 1' _ 1 _ 1 - --- - - -- •0 - .._ - 1 _ . . . -- - - ""Hr -. . . 1 V) T .1 1 J 1/ 1 JrJJ -tu - - 6 I- /T b--U f. ) i i J - ! - - | 1 -- - - / 1 •A 1 ]- T . /Ct—• L 1. I r j . - If ~i -- 1 • 1 L. -\ -L- 1 1 Gl t . • -4- 4- • - 1 _ 1 . _ J r _ i -a _7i 1 < I 0 1 0 - 1 1 4 l - hjiEI • T L E S M l 1. - c E. M R E J . i . 1 J L r; 1 '•: 1" _AX A L C R Ei - A T . i O V S H . 1 P _A 1 DL.FI- W T j S T R E S S t i l l . S_ j i 1 1 r 1. i r 1 1. i : J _ 1 [ I I I I I 1. I M I i T T V E G R E E K / ' S R B G r M E K / C O W > R E S S I O K / J P A R A ' Q L E 1 T 1 Tl 1 1 T r N 1 ( . 1 . M I 1 1 J 1 M M " 1 t 1 1 O 1 G R A I N ' 1 - T3 BYF~< m ILQAD 1 j r T I J I I I . _L. ' :PE n 1 -J I 1 TAGE. F - 1 1: r i-i A SHOWN/ 1 R C E N C 0 :_VG_I_I J.AJ.LL 1 l 1 s T 1 .1. 1. T. . I T 1"' n - 1 T?fl KG . . . . . 1 J J 1 U J . J 1 j | . IT 1. .1.1 I 1 S I R 1 IVJ AS: : k k 1 1 :PE i ' - — I O R E E P L < C E N / T A - * t O F L C O I A L . _ E L A S 1 R _LG_ L L LL .El - Li 1 ITO: 11 _ L I . . J 1 1 . . . 1_ ? t ! i 111 1 U J u . - -TiRAlNL ? 111 r C M 1 T T T PAR 1 C U L A - _ 1 i n ' i 11 1 M i r 1 r 1 1 i i 1 I I I I -II 1 Table 1 - SCHEDULE OP STEP-BY-STEP LOADING-UNLOADING TESTS (AIR-DRY CONDITION) Load Level L 0 A D I. N G U ] L 0 A D I. N Gs kips 4 8 12 16 18 20 22 24 2fi 20 16 12 8 4 0 Per cent of max. load 13 26 39 52 59 65 72 78 91 65 52 39 26 13 0 of controls Specimen Time duration of sustained load at each I Load l e v e l i n minutes A-1-5 5 5 5 20 225 5 5 5 20 330 A-1-7 5 15 15 20 15 5 5 5 15 180 A-1-4 5 5 5 5 1510 1500 5 5 5 15 3095 A-l-3(a) 5 30 25 25 30 135 (b) 5 15 25 35 5 15 35 195 (c) 5 15 15 15 15 5 5 5 5 5 10 135 Table 2 - SCHEDULE OF STEP-BY-STEP LOADING.-UNLOADING TESTS (INTERMEDIATE CONDITION) Load Level L 0 A D : [ N G. U N ] _ 0 A D I N G j kips 4 8 10 12 15 16" 8 4 0 :| Per cent of max. load 24 48 60 72 89 96 48 24 0 of controls Specimen Time duration of sustained load at each load I Level i n minutes M-1-2 5 60 60 5 5 215 M-1-9 5 5 5 75 5 10 145 M-1-3 5 20 30 10 . 5 15 155 M-l-10 5 5 5 1040 10 20 1250 M-l-4(a) 5 5 30 10 75 (b) 5 5 5 60 5 10 150 M-l-7(a) 5 5 30 5 10 70 (b) 5 5 5 30 5 • 10 115 Table 3 - SCHEDULE OF STEP-BY«STEP LOADING-UNLOADING.TESTS (GREEN CONDITION) Load Level 0 A N "f f U TrX""0""A~"D I N G. klpsj j Per cent of max. load of controls 8 10 12 14 23 46 58 69 81 46 23 Specimen Time duration of sustained load at each load l e v e l i n minutes  G-1-9 G-1-5 G-1-3 G>l-6 G - 1 - 7 U ) (b) 5 10 10 5 10 75 5 5 962 20 1025 5 20 20 id"- 5 5 90 5 15 30 . 10 5 15 135 5 25 25 10 95 5 25 25 25 15 5 10 150 (a) 1st. cycle of r e p e t i t i v e loading. (b) 2nd. cycle of r e p e t i t i v e loading. (c) 3rd. cycle of re p e t i t i v e loading. T a b l e 4 - 0 R E E P ; : D/A T A f O R D ; O U G L A S - F I R L O A D E D I N S T E P - B';' Y - S T E P M A N N E R;; A T S U C::C;E S S I;V.E.L I • 1 s t . iS-"t e p • - I T — ^ - — ' 2nd f S' t e p : 3 r d . S t e p S t r e s s D u r a t i o n -:~ --( 3 R E; E . ? V S t r e s s D u r a t i o n G R E E : 3  S t r e s s H D u r a t i o n • C 2 K E E P S p e c i m e n L e v e l - .'.->of-- • • L o n g i  R a d i a l Tangen-: L e v e l of. L o n g i  R a d i a l ' T a n g en f 5 L e v e l o f L o n g i  R a d i a l Tangen Sustained t u d i n a l . t i a l S u s t a i n e d t u d i n a l t i a l ; : S u s t a i n e d t u d i n a l t i a l ( p s i . 5 S t r e s s S t r e s s i S t r e s s (minutes) (micro-. .nches p< 5 r i n c h ) ( p a l . ) (minutes) (micro- .nches pe .r Inch) ( p s i . ) (minutes) (micro-! . n c h e s p e r i n c h ) 0-1-1 : 2020 5 10 0 0 : 3030 5 10 0 0 4040 10 30 0 (18*)* (27#) A-1 - 5 1940 5 20 . ; . : .o! . . 0 2910 20 3 3 ; 3880 5 45 7 (25*) (37*} (49*) A-l-7 1920 " i 5 0 o .. o 2880 15; 90. : 0 7 ' 3840 • • ;15 85 • 6; ' 2 0 (25*) (37*) (50%) A - l - 4 ; 970 i o - . • 0 : .; ' •. o' 1940 .5 : • • ; 15 0 0 1-2910 ;: 5 30 3 = A~l-3(a) (12*) j (25*) '. (38*) 1 9 4 0 :::30 :. 0 2910 60 0 ; ... . 0- ! 3880 \ ; 25 . 80 .. 0: 0 ;.'('!)) {26%) : (38*) (51%) ' = 5": ;' "20 . . .• - ; . . 0 15 50 6 7 • : 2 5 ; 70 •• • S\. 7 "••"•UJ .1 3:' 30. :. :. 3 ; 15. '. .  45';. 6 • 1 0 : 1 .'. ".. 15 ho •:• 9r \ : 1 0 M - l - 2 1000 :| '5 cr_... 0 2000 60 150 - 1 7 # -54 : 3000: ; 60 330 • -24; ; -45 (23%) (45*) (68*) M-l-Q 950 5 20 - 3 • -3 1900 5 50 10 13 2850 5 150 37: 38 (25*) (51*) 80 (76%) M-l-3 1000 . i 5 50 ;• 0 : .• 3 2000 20 3 7 • 3000 30 270 ; : -6; •' -7 (23*) : ; (45*) . . 65 ;(68^)- M-l - 1 0 950 40 ••: -3'r 6 1900 . . 5 . 7 10 i 2860 • •; 5 80 : . 13 M-l -4(a) (19%) (39*) 65 (5%) 1000 *: ; ; 5 ' ; ; • 25 •: V 0; • 3' • j 2000 5 -13 : 24 : •\ 2500 : 30 170 •;-57;:- 74 (b) (24*) j , .. ; .. (48*) • (60%) ••'I;5' " 40 13 ; • 5 50 • 20 : ; 35 : - 1 0 7 M-l-7(a) 9 5 0 : 20 :-• 0 o : \ 1900 : • - .5 ; • 25 • ; 3 • • -3;.;. '"2860" : 30 185 .' . 4or:.: : 18 (20%) ........ (40*) (61%) ..-: Ms; 20 • o; 0 5 50 ; 3 6 55':; . . 10. G-l-9 950 : : 5 0 o; *. 1900 10 40 - 6 ?\ 2860 10 1190 -150: (28*) (57%) -(86*)- G - l - 5 1000 5 20 - 3 -3 2000 5 75 -13 - 1 0 2500 962 3330 -124: -251 (31*) (61%) (76%) G-l-3 1000 5 0 p i 0 2000 20 90 -19 - 2 4 • 2500 20 200 ; - 2 9 r : -34 (30*) 30 (60%) (75*) G-l-6 1000 o - 1 0 2000 15 . 150 -30 -35 ! 2500 30 530 ••  - 6 4 ' ' : -38 G - l - 7 ( a ) (31*) ; (61%) "(76*)-950 • •; 5 • 20 - 6 ; - 1900 25 140 -41 0 : • 2380 25 120 : • - 3 8 ; (24*) i (48?.) (60*):. : ; (b) • :':.5. •;. 30 25 135 .-25 0 25 • 75 „ ;, : : : - i i J ! ; -13 H I G/H E R S T R E S S L E V E L S S t r e s s . l e v e l e x p r e s s e d as percentage^ o f specimen's a c t u a l c r u s h i n g s t r e n g t h . ^ N e g a t i v e s i g n i n d i c a t e s n e g a t i v e creep which Is opposite to bulging*'. " " (a) V a l u e s f o r ; 1 s t . c y c l e o f l o a d i n g s (b) V a l u e s f o r 2nd. c y c l e o f l o a d i n g . ; (c) Values f o r 3rd. c y c l e of l o a d i n g . S t r e s s L e v e l ( p s i , ) : 4 t h . D u r a t i o n 8 o f I r S u s t a i n e d S t r e s s ( m i n u t e s ) s : t &~x> C R E E P L o n g i  t u d i n a l T a n g e n  t i a l R a d i a l (micro-inches per inch) 5050 35 90 00 6 (44^) 4850 :20 120 19 20 (62*) • • 4800 :20 175 32 60 (62*) ' : ;5 25 3890 3 7 (50*) ; 4860 •:35- 140 25 34 (64*) ;i5: 5 0 ; 9 13 3560 75 2320 67 - 3 8 (95%) 4000 :10' • 2035:; 83 353 (91%) ' 3570 1015 387Q : 309 232 (73*) 300 :60 ; 760 - 6 4 ; ; 276 (72*) . . .....; . .. ...... .. .. 3570 30 730 71 124 ( 76 * ) ; : : 3000 ;io 1350 - 7 0 -218 (90*) 3000 :io 2820 : - 9 4 - 2 2 0 (92%) 2860 . -25 ' : • ;275 - 4 5 : - 4 7 S t r e s s L e v e l ( p s i . ) 6060 (53*) = 5820 (74*) 5 7 7 0 (74*) 4360 ( 5 6 * ) ;5830 (77*) 3330 5th, D u r a t i o n J o f S u s t a i n e d S t r e s s (minutes) 65 225 ;15 1510 15 S t t e . L o n g i - dRadlal t u d i n a l T a n g e n  t i a l ( m i c r o - i n c h e s p e r Inch) 180 810 445 250 15 270 1100 3 137 95 51 63 -41 6 155 161 77 67 «.44 S t r e s s L e v e l ( p s i . ) 7070 (62*) 5340 (69*) 6800 (88*) 6th D u r a t i o n o f S u s t a i n e d S t r e s s ( m i n u t e s ) 40 1500 S t e p  C R E E P L o n g i  t u d i n a l T a n g e n - : t i a l R a d i a l (micro-*inches per Inch) 240 300 1140 89 267 91 336 Table 5- R E C 0 V E R Y D A T A F 0 R D O U G L A S - F.;: I R U N L 0 A D E D I N S T E P - B Y - S .1.. E P 1st. S t e D . 2nd . S t e p s t St r e s s : D u r a t i o n 1 R E G 0 V E R Y S t r e s s D u r a t i o n R E G-0 V E R Y S t r e s s D u r a t i o n • *R""ff o.o.v ' k Specimen L e v e l of 1 L o n g i  R a d i a l Tangen-: L e v e l of • Lo n g i  R a d i a l ; Tangen L e v e l of ; L o n g i  R a d i a l Tangen Sust a i n e d t u d i n a l t i a l S u s t ained t u d i n a l t i a l S u s t a i n e d t u d i n a l t i a l S t r e s s ( p s i . ) S t r e s s (micro-! S t r e s s ( p s i . ) (minutes) | (micro-' .nches per inch) (minutes) Inches per inch) ( p s i . ) (minutes) (micro- .nches p< ar inch) 0-1-1 5050., (44*)* 5 20 0 0 4040 (35*) 5 0 1 0 0 3030 (27*) 5 0 0 0 A-1-5 3880 5 0 0 2910 ;:: 5 50 0 . " • 7 1940 5 50 0 7 (49*) {37%) 40 (25*) A-1-7 3840 5 ; 50 . 13 10 2880 . . v . ; 5 1 3 : ; 10 1920 ; 5"': : • 50 13 17 (50*) (3&*) (25/10 A-1-4 3890 5 30 0 10 2910 ; 5'i • 1 5 0. 3 1940 ": 5 ; • 2 5 •. • 0 7 (50*) (38*) (25*) A-1-3U) 1940 25 0 0 0 970 30 0 0 : 0 : 0 • ' 135; ' ' 100 . 3 '." 13 {26%) (13*) • : (0*) (b) 2910 5 20 3 10 1940 • 15. • 10 :. 6 6 970 •: 35 25 • ' 10 10 (38*) (26*) (13*) (c) 4860 5 25 6 10 3880 30 3 2910 5 50 3 17 (64*) (51*) - !... (38*) M-1-2 2000 5 20 0 6 1000 5 30 3 : 3 0 215 170 27 32 (45*) 44 {23%) (OJ.) M-1-9 1900 5 170 20 950 10 400 17 \ ;80 ; 0 145 700 0 -16 # (51*) (25*) • ' i 400 (o*) M-1-3 2000 5 195 0 6 1000 1 5 i o ' i • 1 0 1 5 5 ; • ; 1050 27 32 (45*) {23%) 34 ;(o*) M-l-10 1900 10 185 -3 57 950 : 20 • 530 105r> i • 0 • 1250 1520 60 i 64 (39*) {19%) 75 M-l-4(a) 1000 10"" 50 0 3 0 20 0 ; •'' 3 t : . (24*) {0%) 140 - . .. (b) 2000 5 25. 0 7 1000 10 ."• 44 0 150 390 -12 84 (48*) (24*) 10 •' (0*) M-l-7(a) 1900 5 15 0 0 950 25 " 13. . . 3, . • 0 70 . 25 17 6 (40*) (20*) 10 • 180 {0%) (b) 1900 5 120 3 6 950 10 ' 25 0 115 165 37 54 (40*) {20%) 260 {0%) G-1-9 1900 5 55 16 - 950 10 13 0 75 295 -29 (57*) -47 (28?.) (0*) G-1-5 1000 (31*) 20 350 10 0 {0%) : 1025: 900 -232 v ; -22. G-3-3 2000 5 55 0 12 1000 • • ; 5 - 200 _Q • 10 1 0 , ; 8 5 .., 600 -29 3 {60%) (30*) 450 -40 Hoi) G-l-6 2000 5 95 -7 0 1000 ; '..15 -10 ; : 0 : "115. '. ; 540 -67 -29 G-l-7(a) {61%) 50 -12 10 ( 3 1 * ) ; • (0*) ;' 950 10"" 0 95 10 3 (b) (24*) 17 {0%) : 1900 5 100 -22 950 10 350 -32 : 17 1 0 150 430 -38 34 (48*) 1 (24*) (o*) M A N.N.E-.R: • ' 1 4th. "Stress L e v e l ( p s i . ) D u r a t i o n of S u s t a i n e d S t r e s s (minutes) A T ; , S U C : C . ; E S S I V / E L Y L O W E R S t e p J . : 5th S T R i E s. s L o n g i - t u d i n a l Tangen t i a l R a d i a l (micro-Inches per inch) S t r e s s L e v e l ( p s i , ) D u r a t i o n of S u s t a i n e d S t r e s s ( m i n u t e s ) S :: t e p R E d . 6 \1 ZTT L o n g i  t u d i n a l Tangen t i a l R a d i a l (micro-Inches per inch) L E V E L S ' 6 t h . S t e p Dur a t i o n fl R E G 0 V E R If* of || Long I - J R a d i a l S t r e s s L e v e l ( p s i . ) S u s t a i n e d ! t u d l n a l S t r e s s (minutes)II (micro-: S t r e s s l e v e l expressed as percentage of specimen ' a a c t u a l c r u s h i n g s t r e n g t h . ^Negative s i g n i n d i c a t e s n e g a t i v e recoveryfoulging) (a) Values f o r 1st. c y c l e of unloading. (b) Values f o r 2nd. c y c l e of unlo a d i n g . (c) Values f o r 3rd. c y c l e of unloading. 2020 (18?.) 970 (12*) 960 (12*) 970 (12*) 0 (0*) 1940 {26%) 5 20 15 15 195 5 10 0 0 100 * .-10;'' ' ' 30 75 19 ; 30 60 0 10 45; 6 7 80 . 0. 23 1010 ( 9%) 0 {0%) 0 {0%) • 0 10%) 970 {13%) 10 20 0 0 330 205 41 44 150 175 25 ; 17 3095 180 10 60 , 10 165 0 54 0 {0%) 230 0 {0%) 135 10 245 81 TaMe 6 - MODULUS OF ELASTICITI AND COEFFICIENTS; OF LATERAL,DEFORMATION DURING- LOADING IN STEP-BY-STEP MANNER AT. SUCCESSIVELY HIGHER STRESS,-LEVELS 1st. S t e P • i 2nd. S t e ,_P_ 3rd. S t e P 1 -• •4thJ S t e p 5 t h . S t e P 6th. S t e p Specimen Modulus of C o e f f i c i e n t of L a t e r a l Deformation Modulus of C e e f f i c i e n t of L a t e r a l Deformation Modulus of C o e f f i c i e n t of Lateral Deformation Modulus of C o e f f i c i e n t of L a t e r a l :Def ormatidn Modulus of :Coeffc±ent oi Def ormal : L a t e r a l :ion Modulus : Of C o e f f i c i e n t of L a t e r a l Deformation E l a s t i c i t y During Loading During Creep E l a s t i c i t y During Loading During ; Creep E l a s t i c i t y During Loading During Creep E l a s t i c i t y During Loading . During , Creep E l a s t i c i t y ; During Loading During Creep E l a s t i c i t y During Loading During Creep (1000 psi.) M* MT Mr (1000 p s i j MA Mr M« Mr (1000 p s i ) MA MT M* Mr (1000 psi} Mr M# Mr (1000 p s i ) MT M« Mr (1000 p s i ) M« Mr 0-1-1 1800 0.232 0.406 0.000 0.000 1800 0.211 0.486 0.000 0.000 1740 0.186 0.490 0.000 0.000 1710 0.176 0.448 0.000 0.067 1710 0.229 0.458 0.017 0.033 1710 0.285 0.442 0.012 0.025 A-1 -5 2110 .175 .305 0 0 : 1980 .196 .339 .150 .150 1940 .236 .362 .133 .156 1870 .227 .394 ; . i58 .167 1850 .278 .410 .169 .191 A - l - 7 1690 .349 .448 0 ••0;' 1780 .359 .481 • 0 •; .078 1720 .352 .486 .071 .236 1720 7-363 .493 : .183 .343 1720 .432 .544 .214 .362 A - l - 4 . . . 2060 : .528 .336 0 Ho;. 2060 .344 .343 0 0 2020 .346 • 369 .100 : .100 2020 .346 .392 ; .120 .280 1940 .392 .408 .204 .309 1870 .392 .427 .297 .304 A - l - 3 ( a ) 2200 - .995 '. - . ; o 1940 .183 .456 : 0 0 1870 .248 .485 . • o; ' ; 0 . > (b) 2020 : .819 1940 .178 .450 .120 / .140 1940 .236 .450 .086 i .100 1940 .248 .456 .179 .243 (o) 1900 .208 .600 0 : .': .100 1870 • .208 .423 .133 .222 1870 .238 .433 .'.225. ; .250 1870 .264 .423 : .180 .260 1830 .258 .449 ; .234 .252 1830 .294 .564 .234 .295 M-l - 2 1750 .530 .625 0 ;*:o- 1670 .479 .525 -.113 - . 3 6 0 1540 .415 .470 -.073 -.136 1 • M-l-9 1790 .444 .912 -.150 -.150 1500 .330 .661 H200 .260 1460 .331 .626 .246 .254 1400 .310 .592 .029 -.016 M-l-3 1600 .391 .444 0 .060 1480 .256 .388 .038 .082 1490 .253 .387 -.022 -.022 1470 .215 .328 .041 .179 M-l-10 1900 .539 .808 .075 .150 1830 .531 .635 il08 .154 1800 . .526 .623 .125 : .162 1800 .505 .525 .080 .060 M-l-4(a) 1790 .573 .475 0 \ .120 1610 .306 .460 -.200 : .369 1560 .298 .460 -.336 \ .435 (b) 1660 .450 .465 0 \ .325 ! . . . 1600 .292 .439 -.060 .400 1600 .250 .431 -.286 -.200 1600 ; .293 .446 -.084 .364 • - M-i-yia) 1980 .775 .665 0 [ 0;; 1670 • 475 .491 .120 - , 1 2 0 1670 .466 ; .482 .216 ; .097 (b) 1980 .742 .621 o 0 1640 .466 .480 .060 .120 1610 .434 .463 .109 : .182 1520 .451 .475 : .097 .170 G-l-9 1420 .461 0 1400 .342 _ -.150 - 1240 .252 - . -.126 • G - l - 5 1560 ; .275 .710 -.150 -.150 1330 .234 .482 -.173 -.133 1390 .158 .450 -.037 -.076 G-l-3 1850 .338 .618 0 ; o . 1670 .282 .598 -.211 -.267 1470 .309 .494 - .145 -.170 1430 .237 .444 -.052 -.161 G-l-6 1820 .360 .828 0 -.333 1540 .228 .440 -.200 -.233 1350 .227 .354 -.121 -.072 1280 .208 .344 -.033 -.078 G-l-7(a) 2210 .736 - -. 300 : • - 1640 .405 .540 - .293 0 1590 .347 .533 -. 316 .025 (b) 1900 .621 - -.200 1730 .382 .526 -.185 0 1700 • 354 .504 -.173 -.173 1700 . 307 .493 -.164 -.171 1700 1 .260 .470 -.037 -.040 (a) Values f o r 1 s t . c y c l e of l o a d i n g . (b) Values f o r 2nd.:cycle of l o a d i n g . (c) Values for;3rd.cycle of l o a d i n g . Table 7'- MODULUS OF ELASTICITY AND COEFFICIENTS OF LATERAL DEFORMATION DURING. UNLOADING- IN STEP-BY-STEP MANNER AT SUCCESSIVELY LOWER STRESS LEVELS „st. S t e P 1 2nd. S t e p 3rd. S t t e JP /. • • . 1 4 t h . S t e p —4 5th. S t e P 6 t h . t e n Modulus | o f C o e f f i c i e n t peformat of L a t e r a l : -ion Modulus of C o e f f i c i e n t peformal of L a t e r a l :ion Modulus of C o e f f i c i e n t of L a t e r a l Deformation Modulus Of. : C o e f f i c i e n t of L a t e r a l R e f o r m a t i o n Modulus o f C o e f f i c i e n t of L a t e r a l Deformation Modulus : of C o e f f i c i e n t of L a t e r a l : Deformation Specimen E l a s t i c i t y Dur1 Unlos .ng id ing Dur Recc 'ing >very E l a s t i c i t y : Fur 3 Unlos Lng Lding Dui RecoTi 'ing rery E l a s t i c i t y . ... During Unloading During Recovery E l a s t i c i t y Dui UnlO£ 'ing iding- During Recovery, E l a s t i c i t y During Unloading During Recovery E l a s t i c i t y During Unloading i During ' : Recovery (1000 ps 1.) M* Mr M# Mr (1000 p s i ) MM Mr M« Mr (1000 psi.) Mr M# Mr (1000 p s i ) Mr M* Mr (1000 p s i j Mr M* Mr (1000 p s i ) M R Ma O - l r l 1800 0.264 0.464 0.000 0.000 1710 0.188 0.443 0.000 0.000: 1740 0.169 0.531 0.000 0.000 1770 0.177 0.563 0.000. 0.000. 1740 ; 0.243 0.504 0.000 0.000 16600 •• 0.430 0.430 0^000 0.000 A-l -5 1580 .163 .302 0 1900 .194 .369 : 0 .140 1900 .194 .349 0 .140 1900 .186 .363 i i o o .300 1900 .318 .342 .164 •; .176 • A-l -7 1780.. .291 .384 .260 : .200 1850 .405 .575 . ^.325 .250 1750 .376 .500 .260 : .340 1850 .410 • 536 .253 .400 1750 .420 .500 .143 .097 A - l - 4 1910 .328 .382 0 ;.333 1900 .320 .341 :.0 . .200 1870 .343 .356 0 • .280 1870 .330 .386 .0 , .167 2060 .380 .392 .056 \ .333 A-l - 3(a) 1880 .292 .745 0 o 1940 .241 .450 ' ; 0 0 2200 * .241 .462 .030 ; .130 (b) 1800:, .301 .652 .150 .500 1830 .621 .650 :.600 .600 1870 .560 .432 .400 j .400 2040 .234 .445 .134 .155 ( c ) 1800 : .280 .602 .240 \ 0 1800 .264 .429 ; .100 ••..233 1830 .241 .423 .060 .; .294 1760 .240 .416 . : 0 : • .288 1800 :• .251 .508 0 : .327 1800 .282 .542 .024 .331 M-l-2 1540 .406 .542 0 «300 1540 .384 .482 ;.100 .100 1600 .362 .461 .159 ; .188 • . : M-l -9 1240 .314 . .536 .118 .259 ; 1190 .297 .505 :.042 .200 .142 .244 0 ! .023 • : • ' . .. • , . • M-l-3 1350 .382 .424 0 .038 1370:' .242 .368 .025 .025 1250 .234 .360 .026 ; .030 ! M-l-10 1590 .480 .532 -.016 ; .308 1490 .494 .646 .064 .198 » . .354 .382 .046 : .049 M~l-4(a) 1600 .424 .461 0 .260 1600 .300 .451 0 .150 . • :>.''. ' ' . . . '. w i t ! (b) 1610 .430 .452 0 .280 1410 .341 .392 -.043 .314 1450 .240 .421 -.031 • \ .216 - i ! M -1 -7U) 1640 , .496 .521 0 0 1590 .424 .460 .520 .120 - .388 .467 .670 \ .240 I (b) 1490 .490 .502 .025 .050 1440 .476 .492 .056 .139 1540 * .463 .475 .224 ! .327 G-l-9 1150 .386 - _ .291 , - 1270 .334 - i .050 - - .240 - -.098 \ G-l-5 1130 .211 .330 -.134 J .028 .041 .218 -.258 .024 ! G-l-3 1390 .278 .401 0 : .218 1370 .250 .416 -.045 .050 - .101 .262 -.129 ; .013 G - l - 6 1220 .182 . 292 -.074 T o 1110 .135 .223 -.089 -.022 - .101 .110 -.124 -.o54 I : G-l -7(a) 1500 .521 .564 -.240 .; .200 . . . - .400 .526 -.300 .300 • (b) 1360 .489 .560 -.220 .170 1560 .440 .520 -.092 .049 .346 ; .482 -.088 : .079 1 (a) Values f o r 1 s t . c y c l e of;unloading. (b) Values f o r 2nd. c y c l e of unloading. (c) Values f o r 3rd. c y c l e of unloading. T a b l e 8- VALUES ERflK FINAL S T A T I C T E S T S IN C O M P R E S S I O N P A R A L L E L TO G R A I N FOLLOWING C R E E P - R E C O V E R Y . ; T E S T S - M o i s t u r e - S p e c i f i c M a x . M a x . M o d u l u s P o i s s o n 1 s C o n t e n t G r a v i t y S t r e s s S t r a i n !• ' o f R a t i o S p e c i m e n : j E l a s t i - foicro- i n y i n J GO ( p s i . ) 1 c i t y , ; ( l O O O p s 3) 0-1-1 CA-1-6* o v e n - d r y 0.472 1L400 13200 9*6 0.497 7300 6000 1890 i0.372 0.402 A - l - 5 9 .6 0.504 7860 7300 A - l - 7 10.2 Oo54l 7760 13,050 A - l - 4 9«3 0 .492 • 7750 6700 A - l - 3 9 .6 0.492 7600 6200 C M - 1 ~ 1 # . 1 9 . 9 0.491 4190 4400 1610 0.210 O.596 M-l-2 20,8 0.491 4400 4800 M - l - 9 20,3 0.518 3720 4720 M - l - 3 21o8 0.490 4400 5500 M - l - 1 0 20.0 0.541 4850 7900 M-l-4 20.0.. 0 . 5 0 0 4180 4650 od-i-io* 63*0 0.547 4100 3850 2000 0.342 0.651 G - l - 9 46.9 0 .545 3290 4300 G ~ l ~ 5 60.5 0 .498 3280 6240 G - l - 3 6 5 . 5 0.504 3320 4250 G - l - 6 62.1 0.499 3250 6600 G - l - 7 5 7 . 4 0 .547 3900 4850 C C O n t r o l s p e c i m e n s - w e r e n o t s u b j e c t e d t o c r e e p - r e c o v e r y t e s t s . Table 9 - PERMANENT SET AND STRAIN RECOVERY OF DOUGLAS-FIR TESTED FOR CREEP . Specimen P e r m a n e n t S e t St r a i n Recovery Radial Tangential Longitudinal Percentage of A x i a l Creep (micro-inches per inch) 0-1-1 0 17 270 51.8 A-1-5 48 77 300 70.4 A-1-7 48 91 370 53.1 A-1-4 270 -56.5 A-3-3(a) 0 100.0 (b) & 10 40 87.3 - (c) a 232 700 55.5 M-1-2 - 2 7 * 80 83<.5 M-1-9 0 -16 750 77.7 M-l»3 -27 -127 490 79.9 M-l-10 138 29 1440 64.6 M-l-4(a) -32 43 100 60.6 (b) -32 40 160 81.9 M-l-7(a) «• -6 50 78.2 (b) 34 -19 80 90.6 G-1-9 -30 220. 82.1 G-1-5 60 -35 800 76.7 G-1-3 -22 -20 175 89.4 CE-1-6 -67 -29 460 87.0 G-l-7(a) & a 30 89.3 (b) 4* 60 180 88.8 * No values recorded due to accidental disturbance of the l a t e r a l deformation apparatus. (a) Values of 1st. cycle. (b) Values of 2 n d . cycle. '(c) Values of 3 r d . cycle. Note: Pages 46-67 oversized and are containod i n aeeeapanying- see. p-ij Library. UBC November 2nd, 1962. 

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