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Deformation of wood under load Siopongco, Joaquin Ordonez 1962

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D E F 0 R-: M A I I O N  OF  WOOD  U N, D E R  LOAD  by  Joaquin Ordonez SIOPONG-CO, B. S • C . E., Mapua Institute of Technology, Philippines, 1953  A thesis submitted i n 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 C i v i l Engineering; THE UNIVERSITY OF BRITISH COLUMBIA August, 1962  In presenting  this thesis i n p a r t i a l fulfilment of  the r e q u i r e m e n t s f o r an advanced degree a t t h e 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 r e f e r e n c e and s t u d y . for extensive  I f u r t h e r agree t h a t p e r m i s s i o n  c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y purposes may be  g r a n t e d by t h e Head o f my Department o r b y h i s  representatives.  I t i s understood t h a t copying o r p u b l i c a t i o n o f 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 n o t be a l l o w e d without•my w r i t t e n  permission.  JOAQUIN 0. S . I 0 P 0 N G C 0  Department o f  C I V I L ENGINEERING  The U n i v e r s i t y o f B r i t i s h Vancouver 8 , Canada. Date  August,  1962  Columbia, •  ABSTRACT 7'  Creep  '  and recovery  g r a i n were  four  Specimens  were  Instantaneous  creep  measurements  served' over  successively  are  green  lateral  also  of  All of  the  is  made  minutes  observed  to  ob-  twenty-flve  during unloading  were  as  well  m a i n l y due  as  at^  to  negative  moisture  appeared" t o be more marked i n  oven-dry  show t h a t  during the  change  periods  C r e e p was  as  walls.  yC{  during, the  corresponding the  eac:h s t a g e .  well  intermediate•and air-dry s p e c i m e n showed l e s s  the con-  creep  than  specimens.  tangential),  for  recovery  deformation,  those  predetermined  levels.  than i n the  The o n l y  Results  from  stress  In general,  air-dry  was  a  d e f o r m a t i o n as  ranging from f i v e  cell  specimens  ditions.  taken at  moisture.  up t o  i n d i c a t i o n s that': creep  i n the  Creep,  i n stages  recovery  and n e g a t i v e  present  the  were  lower  of  a x i a l and l a t e r a l  periods  Similarly,  There  loaded  the  2 i n . D o u g l a s - f i r - specimens  different^levels  load.  creep  i n compression p a r a l l e l to  c o n d u c t e d on 2 i n . by  4- i n . l o n g a t  hours.  tests  the values  =• - — -  deformations  were  I n l o a d were  the  ;  load rise  p e r i o d of  of  were  creep,  (both r a d i a l entirely  higher  of and  different  indicating that  entirely  always  coefficient  the  Tcie y^/s  different. than those  for  the:;  creep.  specimens  tested  showed a r e c o v e r y  l o n g i t u d i n a l creep. up o f  two p a r t s ,  This  indicates  recoverable  of  that  more t h a n creep  and permanent  50$  i n wopd  creep.  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 greatlyappreciated. 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 C i v i l Engineering. Appreciation is also due to Mr. K. G3. Rensom,.. Superintendents 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 . . . . . . . . . . . . . . . . . . . ACKNOWLEDGMENTS.  . .ill  ILLUSTRATIONS. Part I. II.  INTRODUCTION . . . . . . . . . . . . . . . . . . . . . .  yr 1  DESCRIPTION OP TEST MATERIAL . . . . . . . . . 3 Species Used" . . . . . . . . . . . . . . . . 3 Type and Preparation of Test Specimens . . . 4  III.  MOISTURE CONDITIONS AT TEST Conditioning of the Specimens  IV.  EQUIPMENT USED Testing Machine: Stress-Strain Recorder Lateral Deformation Apparatus  VJ.  i i  6: . 7 9 9 9 14  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 DETERMINATION . . . . . . . . . 24 Moisture Content. 25 S p e c i f i c Gravity. . ... . . . . . .27  VII.  RESULTS AND DISCUSSIONS 27 Creep and Recovery. . . . . . . . . . . . . . .27 Creep-Time Relationships. . . . . . . . . . . . . 30 C o e f f i c i e n t of Lateral Deformation. . . . . . 37 Step-wise Loading and Modulus of E l a s t i c i t y . 39 E f f e c t of Creep-Recovery Tests on the Subsequent: Stress-Deformation Relation . . 41 Permanent:, Set 43 Conclusions . . . . . . 43 LITERATURE CITED  45  ILLUSTRATIONS  FIGURES  •  1  . . "..  2  .  .  -  •  PAGE  . • • .. • • • . ..... v  .  .  2a  • • • .  .  .5  .11 . 1 2  3  .  4  . . . . . . . . . . . . .  5 11 -  .  .  16 26  10.  .31*36  17. . . .  52-58  PHOTOGRAPHS  1  .13  2 & 3 . . . . . . . . .  20  TABLES  1, 4  2 & 3. r  . .  9 . . . . •  23 46-51  GRAPHS  1 -  9  .  59-67  Part I INTRODUCTION Wood, which was among the earliest materials to he used for construction, has long had an established place in the major f i e l d of structural engineering.  Nowadays, through  the wide application of results from fundamental and applied research, novel designs of large wooden structures are possible, 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 i n this modern world of mechanization and automation.  In the near  future, prestressed or reinforced wooden members w i l l 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 l n 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 m a n y m a t e r i a l s , a  constant  lowing  an  increase time may  initial  dependent  until  exhibits  place  it  leads  to  continuously  is 6,  reported  at  of  the  loading, the  U. S.  W o o d (8)  oak b o t h  creep  decreasing  rate  value;  first,  rate  ximately  1500 that  (3)  Douglas-fir  have  exhibit  or,  then a  which  have creep  it cons-  eventually  shown even  that  when  wood, the  proportional limit  psi. creep  in his  Products  shown t h a t  noticeable parallel  Wood a l s o  creep to  the  when  (1,  3,  grain that  as  and  subjected at  to  stresses  there  and compression  is  is  an  appro-  stress.  investigation  found that  for  the  The A u s t r a l i a n F o r e s t  i n parenthesis  Laboratory  Douglas-fir  reported  in tension  proportional limit,  Numbers  exhibits  standard  p r o p o r t i o n a l to  Dietz  elsewhere  Forest  and compression  indication  1  The  is  1  by  l o w as  the  flow,  8} .  7,  Tests  of  increasing  investigations  w e l l below  as  an  at  fol-  subsequent  two w a y s .  limiting  to  failure.  stress  tension  or  diminishing rate  types  white  a  an u l t i m a t e  under a l l  5,  at  of  This  or p l a s t i c  either  and f i n a l l y  Previous  4,  creep  i n one  approaches  rate  strain.  called  when s u b j e c t e d  i n deformation  and behaves  show g r a d u a l l y  tant  an increase  instantaneous  l n deformation,  take  may  force,  wood,  the  compressive  creep  is  Products  refer  of  to  very  creep  behaviour  stresses  below  low.  Laboratory  literature  (1)  cited.  reported  3  observing  increases  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  green mountain a s h specimens almost cent  three  years  of the short  subjected  at stresses time  i n  to compression f o r  r a n g i n g f r o m 10 t o 35 p e r  strength. Part  II  D E S C R I P T I O N OF T E S T M A T E R I A L Species  Used  Douglas-fir importance was  i n world markets  the species As  (Pseudotsuga  chosen  reported  shows  lel  to the  f o r s t r u c t u r a l grades  for this  particular  the f o l l o w i n g average values  and Selection  Material  lumber,  experiment. "Strength Douglas-  i n compression  paral-  41$ 0.45  p s i , psi.. 1,670,000 p s i .  12$ 0.49  2810  4830  3610  7230  p s i . p s i .  1,950,000  p s i .  of the Experimental M a t e r i a l  utilized in this  sawn p l a n k s e l e c t e d Civil  prime  grains 2  the  of  of  o f Woods G r o w n I n C a n a d a " ,  Moisture Content _ Nominal S p e c i f i c G r a v i t y ^ Stress at Proportional Limit Maximum C r u s h i n g S t r e s s Modulus o f E l a s t i c i t y Source  a species  i n F . P . L . T e c h n i c a l N o t e ? N o . 3,  and R e l a t e d P r o p e r t i e s fir  roenzlesll),  w o r k was o b t a i n e d f r o m a  from a stock  Engineering Laboratory,  of Douglas-fir University of  on hand a t British  Columbia.  Based on weight  when  Based on volume  at test  oven-dry. and weight  when  flat-  oven-dry.  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 f l a t 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 f l a t grain faces to a nominal thickness of 2-| inches, the grain direction was determined, and sticks 2i-inch wide were ripped parallel to the grain with growth rings as nearly as possible parall 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 f i n a l size only after they have already attained a moisture content very near the desired f i n a l condition.' In the f i n a l 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-TEST  SPECIMEN/  a l s o t o make three s i d e s of t h e b l o c k s perpendicular  t r u l y and mutually  t o each o t h e r .  Each specimen was d e s i g n a t e d  by a c a p i t a l l e t t e r which  i n d i c a t e d the moisture c o n d i t i o n under which i t was t o be t e s t e d ; a i r - d r y c o n d i t i o n was designated intermediate  by t h e l e t t e r "A",  moisture c o n d i t i o n by "M! , green c o n d i t i o n by 1  "G", and oven-dry c o n d i t i o n by "0". F o r the c o n t r o l s , the l e t t e r "C" was simply  added.  Thus, CA-1-6 I n d i c a t e s the c o n t r o l specimen i n the a i r - d r y condition. Part I I I MOISTURE CONDITIONS AT TEST Creep and recovery  t e s t s i n compression p a r a l l e l t o  the g r a i n were conducted a t f o u r d i f f e r e n t l e v e l s o f moisture?^, namelys 1. A i r - D r y C o n d i t i o n - i n which the m o i s t u r e  content  of t h e specimens a t t e s t was i n e q u i l i b r i u m - w i t h the atmosphere o f t h e t e s t i n g l a b o r a t o r y .  The specimens were gene-  r a l l y very  content.  2.  c l o s e t o 10$ moisture  Intermediate  C o n d i t i o n - i n which t h e m o i s t u r e con-,  t e n t was above 12$ butt below t h e f i b r e s a t u r a t i o n p o i n t of the s p e c i e s which i n t h i s case Is about 24$ ( 2 ) . moisture content  Nominal  f o r t h i s c o n d i t i o n was chosen t o be 20%",  3. G r e e n : C o n d i t i o n - I n which t h e m o i s t u r e content above the f i b r e s a t u r a t i o n p o i n t , t h e m o i s t u r e content  was 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-andhumidity controlled rooms or. chambers that would bring: them to the desired f i n a l 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  10.2$.  Those to be tested in the intermediate conditions were conditioned and stored in a chamber over a saturated solution of sodium sulphate. ture of 7 5 ? F .  The chamber was maintained at a tempera-  At this temperature the relative vapor pres-  sure above the salt solution was such as to result in moisture conditions that would give a nominal equilibrium moisture content ln the blocks of 2 0 $ . Those to be tested In the green conditions were stored , ln a controlled-humidity-temperature room.  To f a c i l i t a t e  the conditioning of these green specimens, they were firstsubmerged 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  heated  at  observed  212° for  During weighed  the  most  an almost  of  first  nearly  at  long  attained  the  specimens weight  tent,  of  sample the  and i t s  d e t e r m i n e d by and S p e c i f i c While  about  moisture  every  20$,  10$,  that  some  slightly  higher  or  rative  for  that  the  first  no two  moistureeof  more  respectively,  For  the  green of  moisture  (See  to  content  only  attained  taken from  the  Moisture  Content-  24).  b r i n g the a  con-  cross-section,  air-dry,  uniform moisture before  than the it  desired was  the  the  test  was  properties in  the  of  level. impein  i . e.,  1$  discarded. not  wood a r e  range  con-  moisture  deemed  nominal value,  ;  testing,  exhibited a  s u c h l i m i t a t i o n was  strength  had  s h o u l d have a d i f f e r e n c e  otherwise  specimens, the  to  conditions,  t h a n 10$ of  2$,  most  two  continued  Periodically,  the  specimens  specimens  and  since  made  lower  finally,  and the m o i s t u r e  and 60$, r e s p e c t i v e l y ,  inevitable  However,  they  content:.  method.  specimens  and  c o n d i t i o n had m a i n t a i n e d  sample b l o c k s  was  were  equilibrium mois-  a n i n c h t h i c h was  attempt  tent  content  their  G r a v i t y D e t e r m i n a t i o n on page  and green  was  specimens  indicating;, that  oven-dry  intermediate of  the  intervals  i n each  was  hours.  d i s t r i b u t i o n throughout the  i n weight  The w e i g h i n g - w a s  required equilibrium moisture  centre  by  twenty-four  more f r e q u e n t l y .  constant  a moisture  It  no c h a n g e  conditioning period,  had very  contents,  until  the  a p e r i o d of  periodically,  when t h e y ture  F and d r i e d u n t i l  below  necessary Influenced the  9  fibre  saturation The  removed  point.  specimens one  at  were k e p t  a time  for  under  Testing  the  testing  was  pounds  and having  ranges,  the  and the  16,000-lb.  80,000-lb.  i n these  machine,  was  of  range,  i n order  With the  ranges  of  load.  graduated  at  100-lb.  graduated  which is  use  that of  l o a d have been  A stop-watch observing  Stress-Strain  was  creep  at  20-lb.  Only  two  intervals,  intervals,  were  an accessory  was  used  men d e f o r m a t i o n apparatus  used or  creep the  load  or  the  constant  recovery  even  measure  the  testing  over  could  load maintainer,  observed to  of  no  be fluctua-  when h e l d time  a  overnight.  intervals  recovery.  Recorder  An autographic Recorder,  four-hundred-  u t i l i z e d i n holding the  i n the  Tate-Emery  experiments.  time  developed.  This  on a B a l w i n of  three  range,  A load maintainer,  while  performed  M a c h i n e w i t h a maximum c a p a c i t y  thousand  tions  USED  Machine  All  period  until  IV  EQUIPMENT  used  conditions  testing.  Part  Testing  these  recorder, to  provide  measured consists  over  the a  Microformer  record of  load versus  a gauge l e n g t h  essentially  of  two  Stress-Strain  of  two  parts,  the  speciinches. com-  10  pressometer which is attached to the specimen and the microformer 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 i s 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 Photograph 1, includes a heavy base supporting: a vertical framework, two pairs of measuring arms and a microformer measuring unit.  Each pair of measuring arms, upper arms and  lower arms, pivots on a common axis  A  or.A-,.  Stable contact  4  W  UPPER ARM CORE.  UPPER  6AUGE RIVG SPECIMEN  FRAME  1  COIL A,-  LOWER  ARM  r-dlSl  " p r r  3 B, I  L O W E R GAUGE  i  RlkG  F19-2-DIAGRAM OF C0MPRE5S0METER  W  13  Photograph 1 Measuring 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 c o i l  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 l n relation to the--coll  unit actuates the rotation of the drum in the recording equipment 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 recovery, either in the radial or tangential directions, a special apparatus was devised.  This apparatus  was designed  153 and p a t t e r n e d a f t e r the one developed and used by Dr. A. H r e n n l k o f f of the Department of C i v i l E n g i n e e r i n g of the U n i v e r s i t y 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 c o n c r e t e c y l i n d r i c a l  specimen.  As shown In F i g . 3> i t c o n s i s t s of two  channel-shaped  s t e e l c o l l a r s A j o i n e d by two bent i s o - e l a s t i c ^ "  strips  which are f a s t e n e d to the c o l l a r s by means of s m a l l screws. The square r i 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 t e s t specimens by two l a r g e thumb:, screws B p a s s i n g through the mid-points of the c o l l a r s .  The i s o -  e l a s t i c s p r i n g s 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 s u b j e c t e d to a l o n g i t u d i n a l compressive f o r c e . The bending s t r a i n s l n the i s o - e l a s t i c s p r i n g s are sensed by two Budd SR-4,  Type C3-141-B e l e c t r i c a l r e s i s t a n c e  strain  gauges g l u e d on the i n n e r and the o u t e r f a c e s of b o t h springs.  A l l Inside gauges C and s e p a r a t e l y a l l ouside  gauges D are connected i n s e r i e s and a t t a c h e d to the a c t i v e and.compensating  t e r m i n a l s of a Baldwin SR-4  Type L S t r a i n  I n d i c a t o r whose readings are n e a r l y p r o p o r t i o n a l to the l a t e r a l s t r a i n s l n the specimen.  With t h i s arrangement,  i n s i d e gauges were a l s o made a c t i v e , but s t r e s s e d from the o u t s i d e ones.  differently  The i n d i c a t o r would then show the  d i f f e r e n c e of the two s t r a i n s which are of the o p p o s i t e  4  the  I s o - e l a s t i c i s an a l l o y of i r o n , 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-LATERAL  DEFORMATION  APPARATUS  ATTACHED TO THE RADIAL SIDES TO MEASURE  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 consists 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 i t s stress w i l l not exceed i t s 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 i n i t i a l force necessary to hold the apparatus In the specimen by f r i c t i o n alone. When calibrated, the two apparatuses showed a sensit i v i t y of 3.18 and 3.36 which means that a strain reading of 1 micro-inch per inch i n 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.  18  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 i t s cross^sectional dimension 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, i n order to prevent any increase or decrease i n the moisture content of the specimen while the testing was i n 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 i n weight before and after testing  of the test specimens reported i n 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 compressometer rings) was.accomplished with the aid of four set-up posts, which, together with the rings, formed a r i g i d frame (See Photograph 2 ) .  One lateral deformation  ring is clamped on the tangential sides of the test block  19  to measure strain i n 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 positions . Photograph 2 shows, the four rings and the set-up posts forming a r i g i d 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 i n 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, n = 0.012 t  inch per minute.  Photograph 2 L a t e r a l d e f o r m a t i o n and compressometer r i n g s r i g i d l y connected w i t h four set-up posts before attachment to a specimen.  Photograph 3 L a t e r a l d e f o r m a t i o n and compressometer r i n g s i n t h e i r p r o p e r p o s i t i o n s on the specimen.  shown  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-deformationcurves, the two Poisson's ratios, -^^/z culated.  The Poisson's ratio  a  n  d  or ^ i  ^t-t *  w e r e  c  r  cal-  represents the  numerical value of the ratio of the strain along the radial or tangential direction to that along the longitudinal direction 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 stepwise 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 arbit r a r i l y , 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 i n 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 i n the lateral directions. 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  f i 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 i n a similar step-by-step manner (See Tables 1, 2 and 3 for unloading schedule).  T a b l e 1 - SCHEDULE OF STEP-BY-STEP LOADING-UNLOADING . ."' . (AIR-DRY CONDITION) Load Level kips Per cent of max. l o a d of controls Specimen  A-l-5 A-l-7 A-l-4 A-l-3(a) ••(b)  0 12  L  4  6 26  13  5 5 5 5 5 5  (°)  D  18  39, 52  Tine  5  A lo"  59  duration  5. 15 5 30 15 15  5 15 5 25 25 15  I. . N G 20 - 22  0 20 16 12  4  a 0  65 52 39 26 13  0  U 1Y L  24 28  72  65  78 91  Mrl-2 M-l-9  M-l-3 M-l-10  M-l-4(a) (b) M-l-7(a) (b)  L  4 24  0  8  1510  20 . 225 20 15 1500 35 15  A  D  10  48  60  15  60 5 20 5 5 5 5 5  5  5 5 5 5 5 5 5  N  G  12  15  72  89  96  8  75 1040  60 30 5  level  5 5 20 330 5 5 15 180 5 5 15 3095 • 25 30 135 5 15 35 195 5 5 5 10 135  5 5 5  5  5  U N 1.  8  48  of sustained l o a d at i n minutes  60 5 30 5  30 5  [  16  *  ePirne d u r a t i o n  A D I N.  o f s u s t a i n e d l o a d a t e a c h I Load i n minutes  T a b l e 2 - SCHEDULE OF: STEP-BY-STEP LOADING.-UNLOADING •' (INTERMEDIATE CONDITION) Load L e v e l kips Per cent of max. l o a d of c o n t r o l s Specimen  TESTS  10  A D I N G  4  0  24  0  e a c h l o a d ]L e v e l  5 5 5 10 5 5 5  30  0  TESTS  5 10 15 20 10 10 10 10  215 145 155 1250 75 150 70 115  T a b l e 3 - SCHEDULE OF STEP-BY-STEP LOADING-UNLOADIN&.:TESTS (GREEN CONDITION) Load L e v e l kips P e r c e n t of max. l o a d of c o n t r o l s Specimen  G-l-9  0-1-5 0-1-3 r GE-1-6  G-l-7(a) (b)  0 .  L  4  A  8 46  23 Time  5 5 5 5 55  D  10 58  I  N ( 12  14  8  4  69  81  46  23  U N L O A D  d u r a t i o n o f s u s t a Lned l o a d a t i n m inutes  10 5 20 15 25 25  962 20 30 25 25  (a) 1st. c y c l e o f r e p e t i t i v e (b) 2nd. c y c l e o f r e p e t i t i v e ( c ) 3rd. c y c l e o f r e p e t i t i v e  10  5  10 10  5 5  25 loading. loading. loading.  15  5  I N" 4  0  0  e a c h loa<a l e v e l  10 20 5 15 10 10  75 1025 90 135 95 150  24 L o n g i t u d i n a l and l a t e r a l s t r a i n recovery - the creep on.the unloading p a r t of the c y c l e - were observed and r e c o r ded f o l l o w i n g the same technique used i n creep o b s e r v a t i o n . Finally,  the same specimen was  tested i n a  continuous  o p e r a t i o n without stops t o f a i l u r e a t a machine speed •"'"0.012 i n c h per minute.  Each t e s t was  f e l l w e l l below the maximum. a f t e r t h e r e was  c o n t i n u e d u n t i l the l o a d  T h i s f i n a l t e s t was  done only  no f u r t h e r d i s c e r n i b l e r e c o v e r y t a k i n g p l a c e  i n the specimen i n i t s unloaded l e n g t h of time which was testing  state a f t e r a considerable  i n a l l cases equal or more than the  time.  Repetitive  Loading  In t h i s t e s t , the specimen was  loaded as i n the p r e v i o u s  s t e p - b y - s t e p creep and recovery t e s t s . loaded, the specimen was fashion.  Then a f t e r being- un-  loaded a g a i n i n a s i m i l a r  step-wise  F o r each succeeding l o a d i n g c y c l e the s e l e c t e d  maximum s t r e s s - l e v e l was v i o u s one.  made h i g h e r than t h a t of the p r e -  Specimens t e s t e d i n t h i s ty.peoof r e p e t i t i v e  l o a d i n g were n o t . r e l o a d e d u n t i l s t r a i n r e c o v e r y , b o t h and l a t e r a l , was a t l e a s t two  virtually  complete.  hours a t the unloaded  loading cycles. to  of  axial'  A recovery p e r i o d of  s t a t e was  As b e f o r e , each specimen was  allowed between, finally  loaded  failure. Part MOISTURE CONTENT AND  VU  SPECIFIC GRAVITY DETERMINATION  The moisture content and s p e c i f i c g r a v i t y of each t e s t  2  s p e c i m e n were to  the  point  Moisture  determined from a s m a l l sample of  Content  i n the  and  each  a moisture cut  content  following  (1) A f t e r men,  final  sample  as  n a t i o n s ' were  made f o r  the  cross-section  to  of  removed and each by  means  of  nearest  was  core  after  and each  the  the was  Moisture  of  moisture  sawing,  s e c t i o n was  a l l  weighed  balance  w h i c h c o u l d be  (3) T h e m a t e r i a l w a s  there  weighing  the  specitaken  determi-  shells  sepa-  d i s t r i b u t i o n at  the  loose  to  the  graduated  r e a d by  splinters nearest to  were gram  0.01  the  nearest  i n t e r p o l a t i o n to  the  gram.  0.01  controlled  and a f t e r  s h o w n i n F i g . 4.  a M e t t l e r type  0. 10 g r a m / b u t  oven-dry  block.  Immediately  (.2)  the  an i n c h i n thickness  determine  the  d e t e r m i n e d by  test,  about  sections  i n order  was  manners  into  rately  adjacent  failure.  The m o i s t u r e method  taken  5  electric  then put  oven heated  at  no v a r i a t i o n i n w e i g h t  into  a  212°  F and d r i e d  for  thermostatically  a p e r i o d of  until  twenty-four  ho u r s . (4) U p o n a t t a i n i n g 1. e . , was  when a l l  again  the  moisture  carefully  weighed.  (5) T h e oven-dry  this  loss  weight  i n weight  indicates  men f r o m w h i c h t h e  c o n d i t i o n of had been  expressed  the moisture  s a m p l e was  The v a r i a t i o n i n m o i s t u r e shells  was  limited  to  0.1  %,  constant  weight,  evaporated,  the  i n per  of  cent  content  of  between  the  the  material  the speci-  cut. content  core  and  2*  Fig-4  -METHOD FOR  OF'CUTTING MOISTURE  DETERMINATION  CORE  MOISTURE  OF  SHELL  SAMPLE AND  DISTRIBUTION  27 Specific  Gravity  The  specific  to the nearest  g r a v i t y f o r e a c h s p e c i m e n was  calculated  0.001 o n t h e o v e n - d r y w e i g h t , v o l u m e a t t e s t  basis.  Part VII RESULTS AND  DISCUSSIONS  Creep and Recovery Creep and r e c o v e r y from  tests  conditions  and l a t e r a l ,  obtained  to the g r a i n at the four  investigated are presented i n  4 a n d 5.  In g e n e r a l , tions,  both a x i a l  i n compression p a r a l l e l  moisture content Tables  data,  creep,  i n the l o n g i t u d i n a l and l a t e r a l  was f o u n d t o be more marked i n t h e g r e e n  direc-  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 .  only  oven-dry  The  s p e c i m e n showed l e s s e r c r e e p t h a n t h e a i r - d r y  ones. Apparently, present  creep  i n the c e l l  water i n the walls  walls.  While the load  forced  into the c e l l  load,  i s due m a i n l y  Upon a p p l i c a t i o n o f t h e l o a d ,  previously  i s held  constant,  i s relieved.  c a r r i e d by t h e c o m p r e s s e d w a t e r i s t r a n s -  to the fibrous material,  tion.  The r e a s o n t h a t i s probably  was n o t e x p e l l e d .  of the  the moisture i s  c a v i t i e s and t h e p r e s s u r e  ferred  some c r e e p  to the moisture  i s c o m p r e s s e d s o as t o c a r r y p a r t  load.  The  i n wood  thus causing  the oven-dry  further  specimen s t i l l  due t o t h e f a c t  that  deforma-  showed  a l l the moisture  During the rise in load, the specimen undergoes an increase i n 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 w i l l now c a l l negative creep, has been observed to be more marked and predominant In the green specimens than i n the specimens 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 i n the green condition almost a l l of the stress levels showed negative creep. Similar phenomena were also observed i n 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 i n the lateral dimensions was noted during recovery following unloading. Again we w i l l term tnis as negative recovery.  As with  negative creep, there was a preponderance of negative recovery observed i n the green specimens. However, not a l l the stress levels under which negative  29 c r e e p was Por  recorded exhibited a similar negative recovery.  example,  i n Specimen M - l - 2 ,  t h e r e was  n e g a t i v e creep both i n the r a d i a l  and  a  consistent  tangential  directions  b u t no n e g a t i v e r e c o v e r y e i t h e r r a d i a l l y  or  was  recorded.  true with Speci-  men  &-1-3  On  T h i s was  a l s o f o u n d t o be  ( F i g . 15;), b u t  tangentially  i n the t a n g e n t i a l d i r e c t i o n  t n e o t h e r hand, t h e c r e e p and r e c o v e r y i n t h e two  directions  o f S p e c i m e n u-1-6  ( F i g . 16)  both negative.  Such i s the case,  M-l-4  i n their radial  and G—1-3  the a i r - d r y  was  found  directions.  i t becomes o b v i o u s  t u r e c o n t e n t o f t h e s p e c i m e n s had 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 .  the c e l l  structure builds  a d d i t i o n t o the normal When t h e l o a d  of  the f i b r e s .  removal  ture  something  observed  behaviour i n the  the mois-  t o do w i t h  p r e s s u r e i n the water w i t h i n  up c a u s i n g l a t e r a l  expansion i n  o f t h e wood  substance. Its  The w a t e r p r e s s u r e i n t h e  resulting  i n the l a t e r a l  e x p l a i n e d i n t h e same way. suction  walls,  cell  Negative  After reduction  i s d e v e l o p e d and  i s a t t r a c t e d back t o the c e l l  way  contraction,  Hence, n e g a t i v e c r e e p i s d e v e l o p e d .  of the load,  the  I t seems t h a t d u r i n g t h e  distortion  cavities.  i s thus reduced,  r e c o v e r y c a n be or  that  i s s u s t a i n e d , some m o i s t u r e f i n d s  into adjoining walls  such  t o h a v e o c c u r r e d more i n t h e g r e e n t h a n  r a p i d a p p l i c a t i o n of the l o a d ,  be  too, w i t h Specimens  specimens t e s t e d and because  intermediate condition,  lateral  were f o u n d t o  S i n c e n e i t h e r n e g a t i v e c r e e p n o r r e c o v e r y was in  only.  thus  the mois-  causing  30 lateral  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  test  e x p r e s s e d as p e r c e n t a g e s zero l o a d to the s t r e s s against  specimen,  of the t o t a l level  The  creep values,  elastic  strain,  o f t n e c r e e p , were  time a t every creep l e v e l  were f i t t e d v i s u a l l y .  axial  stress  and  plotted  smooth c u r v e  levels  from  lines  are expressed  percentages  o f t h e s p e c i m e n ' s a c t u a l maximum c r u s h i n g ,  stress.  way  By  of e x p l a n a t i o n , the specimen's  maximum c r u s h i n g s t r e s s , s t r e n g t h o b t a i n e d from the g r a i n t e s t  as  used here,  the s t a t i c  performed  after  actual  i s the u l t i m a t e  compression  tne specimen  parallel  Due  tne e f f e c t levels,  to the n a t u r a l v a r i a b i l i t y  of the f i r s t  t y p e of' t e s t i n g ,  e x p r e s s e d as t h e p e r c e n t a g e s  p r e s s i v e s t r e n g t h or each specimen, t h e assumed s t r e s s  as d e s c r i b e d  o f wood, and the a c t u a l  differed  on t h e  for  ©for  b and  time,  compressive  the green specimens. individual  specimens,  and  Each s e t of curves specimen.  of  under v a r i o u s  6 f o r the a i r - d r y  the intermediate c o n d i t i o n ,  a t e s t w i t h an  from  specimens.  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  3' and  to  stress  somewhat  T y p i c a l c r e e p c u r v e s showing the r e l a t i o n s h i p  a r e shown i n F i g s ,  due  o f t n e u l t i m a t e com-  l e v e l s w h i c h were b a s e d  s t r e n g t h of the c o n t r o l  to  had been s u b j e c -  t e d t o t h e s t e p - b y - s t e p c r e e p and r e c o v e r y t e s t s earlier.  as  in Figs.  creepstresses, in Figs. 9 and  10  i s the r e s u l t  of  31  Ip  T I M E . \w  .  ;  MINUTES .  j-f-i-fH-j i r  .L.LiJ.L - L L , ' ! •: !i I i i 1  .LL  it::U±:  • ± L + J f c y : i ^ i M E RELATlf OV-SHIP.I A t DI F B E V . T! - L . i. RI EiL,.j L ST.RES5 LEVELS AlRfDRY SPECIMEN/ U/: CPMPRESSIOV •WtH PAftALLEL. TO GRAlhZ. : S T R E 5 5 ! L E V E L S ARtjlL'JSHOWW L A S P I ; R C E V'fTAGES iii • iii. i • i ' '_4i iL.$ Ti Ki iEiVi6.TiH' ., i ' ; -i OF MS A C T Ui A• L: ; C> ~R O !SHIN'S II iv. ci i. :]:!:HIT:I^:L;: ' " L.I.±jJ_ _ 4-4-1- ! A L : ELASTIC P E R C E t f T A -r-:-Lj- — j ^—-j)•• CREEP, STRAl U P ; TO £ACM PARTICL L iSTiR-ESSl ILlEME Lit"-  x^±H±L:  J  •  STRAW: AS  32  -U  _  j-LL_1.4j._1  _l_L_i._  M M  -U-  UJ  LL"  11 1  •:zl.irp 1 .]_•_. J J 4 J1.LJ uJ  -J±r-UI j_  ;t::;riD  • 4-  -! L  rr  :4W  L.L.L.  . 1 !  1J..I ' J _ JM -U.J-  ! i"  - | _ M - . J J__.L.i_4  JJ-L  mi -bg J to  I  T H~£if  4  J  —  II1 !  1"TT 1 i"i -1  4 4:4 4 } Ii M 1 i 1—M ' '  T  1 4 4  J  as  r r n :  I  ; o... : -|4-' '  -4I  !  iJJ  i  Tl "  4-1-  •0-  j;  TIT d<_:&:  .. -:  ; \u  •  I M ; T ,---._.-_-  T I M E  J  n:  :63 ttJ  JJJ.  -!-M -j-j.4  4 M -]~n M -ri-i-i  i M  TJ  I 1 IP J _1. *ii M U T E S  ——.  44-i-!-J3_.J4j44a-i--!-LL  j !!M'  ]  LlCR_:E P4TiXlM!E^BZU"AXI.CWS.UIP. ; A T ^ , 1 j ; { 1 1 i i  A X I A  El  44  -1  "! L"U"i m" t 1  j-IOL  czq.T  m1m.J..  f!-  f±]  TT4  J ! J MM  tr-i-f-  mJ.__J_JJ_ I  .i L  J  L.l-  1 J __.•••-  LL"LLJ___L ) __!_L '  :  1.!  i;;r]-M-rp"j  „LJ.  ''"XIT'J - h - H j - i - :  .I i  II i l l J_ . .!_.  r l — H-  u  iXllTrrTr 1 _!_]_: . L l l i : ! J.. LI.LLJJ J.J , TT I n i T i jT"  U U -!•--V  XtEI  IHI'T^J-  L  . 1  .tl-LL 1  N4-  "I 1 I ; j !'  M ' 1 . 1i  H-H-&  -</>H  J_!.4.  j. '  L JJ_] U<  4444n4 rrj -  M  M  !1  rsPEcrHiEk : :w . JWFf?tRtyX-d SIREi>S , RALLEL iM^TjEP-B_^5JIE-_1 • • ' ij___A^_n_v_a: M M!'' A C T . U A t:! GFI ITS.: •ARE : SWQV/is/ JT i i J j ,: " rr 1 i j j 1 i ; -H--!~i . I.U ST.REIS/GTW.. m.4." X l X J p l t . CRU..\-UwG „ 4TJT • • j j _ |_t. i:^^fl:p4i^rEA:i:w J A S J : :PE f: T O T A L , : E : L A S T I C LI ! M :L.:E"VE.L4: : |; i . 'STRAW : UP TO j i t i t I tl i . ' M M I i 1 !J._.I.  ; L E V E L S  ; :A\R-_>RV  1. i _i !_,..;I__Q__: • RAW: 1  J  1  4  33  ns::84 IAYI^:LT.cREtrp-^IWE;:. RELAT iOf/SHIP. : AT DI FFEj RE^Tf '•1-STREIS3 Tip: .  POM(kgE5SlCW  PAKA1 I E L TO  LOADING::: FJSTR EiSS ; "X.EV.E L S :  L...J..  C E N T A G E S  -t-rt  P ST R/jui\/  or  ITS  gRAltv\  1  r: V S R E C I  r i T T  .STEP^&Y-  .0--!-  ARE  i A C j r u A L  SJTRET/vSTH. •f{t r — ELASTIC S T R' -Li. E S .SL> | L E V E L .  eebSMitfc  STRAIN UP! T O . EACH.: ; P A R T I C U L A R  TOTAL]  5  F T !"  LL i I  T I M E ; lh/:.Mi:|/UT s:i -; U J "l "i . ; I L.L.. 'illJKlG. 10: - AXIAL ; CREEP-TIME- R E L A TO V S ^ f l P • A T . D I F F E R S * T . S T R E S S 1 : L E V E:LSl<5REEh/: S R E C I M E p : 1IV1 ! C O M P R E S S I O N • P A R A U L F i l  i . i  y  - - U - H  i  ^IJILEVS^.:.!:  AR C  SHOWN/ A S . . : P E . R C J V T A & E S : WIIVG: ; S T R E K / S m l_l  ! i i! j  ^qTi^'Liit  i r•I ; • , iI  1  Tt-  1  -j Ttil _ i  • iH-l-H-, ii i =" ^ i 1 !Jt~r± __  rEtvTAGE. j . * C R _ } E P 1: sTRAI^; ; A S : ; PER ! ? ARTIC STB A M UP TO .: E A C H  ! i I !  _  QtxirrdTA]:. : ELASTIC VEL... 1 U L A P : : 'STRESS r!  ii! •  i  —  37  At about 9 0 $ stress level i t appears that there is a rapid increase i n 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 characteristic 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 i n Tables 6 and 7.  They are  herein referred to as the coefficients of lateral deformation, 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 l o a d and the r a t i o of s t r a i n s d u r i n g the p e r i o d of creep or recovery. In o r d e r t o d i s t i n g u i s h them from the u s u a l Poisson's r a t i o s , ^(A^  and y^f jL  $ we designate the c o e f f i c i e n t s o f  r a d i a l and t a n g e n t i a l deformation by ^^{^  a  n  d  ^C^- *  r e s  P  e c  =  tively. T y p i c a l yl^ diagrams are p r e s e n t e d 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 c o n d i t i o n and i n F i g s . 15 and 16 f o r the green c o n d i tion.  F i g . 17 i s t h a t of the oven-dry  specimen.  The v a l u e s o f the c o e f f i c i e n t of l a t e r a l  deformation,  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 the p e r i o d of creep a r e e n t i r e l y d i f f e r e n t from those d u r i n g the l o a d r i s e ,  indica-  t i n g t h a t the corresponding deformations are e n t i r e l y rent.  diffe-  In a l l the specimens t e s t e d , the yC^3 f o r the p e r i o d  of creep showed c o n s i s t e n t l y lower v a l u e s than those f o r the change l n l o a d . A t almost a l l s t r e s s l e v e l s , the c o e f f i c i e n t of tangent i a l deformation e x h i b i t e d a h i g h e r v a l u e than i t s r a d i a l counterpart.  T h i s i s probably due t o the medullary rays  running r a d i a l l y i n the r a d i a l  i n the wood which r e s t r i c t s  i t s deformation  direction.  During the l o a d i n g p a r t of the c y c l e , some of the sum -/-yO{  r  have been observed t o be g r e a t e r than one, i n d i c a -  t i n g t h a t the m a t e r i a l i n a way opens up.  On the other hand,  the n e g a t i v e s u m ^ ^ y ^ i n d i c a t e s a r e d u c t i o n the  i n volume of  material. Whenever f e a s i b l e , the /C{s  were c a l c u l a t e d s e p a r a t e l y vals.  during  the p e r i o d of creep  f o r d i f f e r e n t p a r t s of time i n t e r -  These v a l u e s appear to become s m a l l e r w i t h  i n time f o r the intermediate  increase  c o n d i t i o n w h i l e the r e v e r s e  is  t r u e f o r the a i r - d r y c o n d i t i o n . Step-wise Loading and Modulus of I l l u s t r a t e d i n Graphs 1, graphs t r a c e d a u t o m a t i c a l l y during  by  2,  Elasticity §, 4,  the  and  5 are  typical  stress-strain.recorder  the step-wise creep-recovery t e s t s i n compression  p a r a l l e l to the g r a i n .  A t ieach l e v e l of l o a d , s h o r t  t i c a l l i n e s were drawn on the h o r i z o n t a l p o r t i o n s graphs.  These represent  was  the..  time increments i n minutes during;,  which creep or recovery, a x i a l or l a t e r a l , was Whenever t h e r e was  of  ver-  recorded.  measurable creep or r e c o v e r y , marking  done every minute f o r the f i r s t f i v e or t e n minutes,  every two  or three minutes f o r the next t e n or twenty  minutes, and  so on,  the time i n t e r v a l s g r a d u a l l y  increasing;  thereafter. Due  to the r a p i d r a t e a t which the l o a d was  the l o a d 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 l o a d Increment. l i n e a r behaviour was  raised,  Such a  observed to e x i s t i n some specimens  even.up to s t r e s s regions  beyond the s t a n d a r d  proportional  l i m i t of the m a t e r i a l , where I t would normally p l o t as  a  40 curved l i n e under t h e o r d i n a r y r a t e ; of t e s t i n g .  Graphs 2 and  4, w i t h l o a d l e v e l s up t o 95 and 92 p e r cent of t h e specimen's a c t u a l s t r e n g t h , r e s p e c t i v e l y , w i l l serve t o i l l u s t r a t e the f o r e g o i n g statement. Obviously., as o r d i n a r i l y i s mainly  the curved portion, of a s t r e s s - s t r a i n graph  obtained by the c o n v e n t i o n a l t e s t i n g method,  due to creep t h a t i s t a k i n g p l a c e w i t h i n the dura-  t i o n of the:.-loading time. In g e n e r a l , however, the s l o p e s of the s t r a i g h t  lines  between two c o n s e c u t i v e loads f o r each graph a r e n o t of equal magnitude. As one goes from one i n t e r v a l t o the next interval,  higher  the s l o p e s have a tendency t o become s m a l l e r , though  not c o n s i s t e n t l y s o . Consequently, because the modulus of elasticity  i s d i r e c t l y p r o p o r t i o n a l t o the s l o p e , a s i m i l a r l y  d e c r e a s i n g Young's modulus i s e v i d e n t from the f i g u r e s i n Table 6. In. the a i r - d r y specimens, the decrease  i n the modulus of  e l a s t i c i t y was of the order of 2 t o 6 p e r cent w i t h the except i o n of Specimen A-1T-3 where a 12$ r e d u c t i o n was noted the f i r s t -  t o the second-step  centage decrease and s l i g h t l y  interval.  from  Generally, the per-  was g r e a t e r i n the i n t e r m e d i a t e c o n d i t i o n  h i g h e r f o r the green specimens, the former,having  a maximum r e d u c t i o n of 21$ and the l a t t e r a maximum of 26$. The  said linearity  unloading,  i n the graphs i s a l s o e v i d e n t d u r i n g  although t o a l e s s e r degree, e s p e c i a l l y d u r i n g the  l a s t unloading been observed  step where a pronounced c u r v i l i n e a r graph has In. a l l  the i n t e r m e d i a t e and green specimens.  41 This the is  curvilinear characteristic  moisture  i n the; wood.  developed  finally during the  the the  causing water  p e r i o d of  curvature It  the  will  of  formation  load  of  increment  of  observed  the  it.  elasticity  application.  to  the  elastic  strain,  of  the  creep.  This  tested  i n the  air-dry  Effect  of  Graphs showing  the  obtained at  a  As  i n the  d i d not  strain  walls  accounts  to  that  releasing  there  true  of  is, of  in a l l  conditions  in a  given stress  way,  the than  upon  decrease  addition portion  the  specimens  while  such a consistent  on the  a  a load  that  in  the  in.another  recovery  be  graiphs  strain for  indicate  and green  Tests  cell  the  trend.  Subsequent  Stress-  Relation 6,  7,  8 and 9 are  load-axial  from  a  other while  plotted  the  stress,  show  suction and  the  This  on r e l e a s e to  found to  intermediate  rate  graphs, the  from  indicator.  two  examples  and l o a d - l a t e r a l  compression  uniform testing  recorded were  was  first  of  same  it  an immediate  Creep-Recovery  Deformation  putting  the, c o m p r e s s i v e  specimens  the  loop,  seems  removal  of  from  This  or  load,  to  curve.  smaller  its  at  out  greater.upon  Or,  attributed  the  water  reverted.  is  on  of  forced  hysteresis  generally  t h a n upon a p p l y i n g modulus  is  unloading  be  is  i n the  had been  creep,  the  also  Upon r e l e a s e  tension  that  c o u l d be  of  the other  parallel about  to  0.012  load-axial graphs  experimental  data  of  typical  strain the  relationships  grain  inch per curve  (radial obtained  was and  graphs •  test  done  minute. automatically tangential)  through  the  42 With,the  exception  trol:, specimen, been  will  of  the  the  be  intermediate  the  specimens, exhibited similar  on the  that  from which the Table: 8 were Also  ticity a  either  of  the  their  each  hand,  that,  have  tests.  which are  those  respectively,  that  straightness  curvature present  is  is  hot  in a l l  of  typical for  very  the  peak  the  Specimen A-l-5,  G r a p h 8 o r 9. that  curves  air-dry  which  also  relationship  A l l the  curves,  i n d i c a t e d maximum  and s t r a i n values  of  4 to  a l l but the  green  8 are  specimen,  ratios  of  properties  the of  corresponding  specimens  strength  order  the  is  con-  as  load  given  in  obtained.  of  air-dry  controls,  the  a  specimens.  exception  and P o i s s o n ' s  condition,  For  other  included i n Table  with.those  the  of  gravity  pressive  conditions,  maximum s t r e s s  comparison of  the  two g r a p h s ,  although  of  and recovery  show a d e v i a t i o n f r o m  showed a d e f i n i t e  specific  creep  last  that  from specimens  a non-proportional stress-strain  to  however,  the  and green  w i t h the  which is  a l l  characteristic  intermediate  G r a p h 7,  to  the  origin,  This  are  and green  curves  from the  pronounced. of  subjected  n o t i c e d from  load-axial  almost  G r a p h 6,  these graphs  previously  It  of  tested  have  than t h e i r 8 per two  the  and the  the  Likewise,  of  specimens,  the  increase opposite  and elas-  this  table  specimens  can be made.  shown h i g h e r the  of  From  individual  controls  showed g r e a t e r  content  modulus  controls.  controls,  cent.  percentage  moisture  ultimate  increase  for  the  strength varying result  was  com-  being  of  intermediate  than  from  A l l  their  5 to  16.  obtained  43 that  Is,  duction the  the of  green All  c o n t r o l , showed  about  20 p e r  higher  cent  was  crushing stress.  noted  i n a l l but  A  re-  one  of  specimens. the  (air-dry,  specimens  tested  intermediate  mum l o a d c o n s i s t e n t l y  at  the  and green) greater  three  moisture  conditions  exhibited strains  than those  of  their  at  maxi-  respective  controls. Permanent  Set  Axial  and l a t e r a l  ( r a d i a l and t a n g e n t i a l )  and s t r a i n recovery  expressed  creep  i n Table  are  tabulated  Each of  the  residual  the  table  it, w i l l  more t h a n h a l f been be  ultimately  classified  which or  other  delayed  formation. not  of  the  s t r a i n values  workers  axial  have  elasticity, Recoverable  Hence,  the  axial  namely,  the  deformation apparatus  i n the  as  the  at  the^  taking  place.  that,  in a l l  of  an e l a s t i c  then  creep after-effect  creep, or p l a s t i c lateral  de-  direction  disturbance  e n d o f .the  cases, had  wood c o u l d  recoverable  accidental at  taken  had t a k e n p l a c e  creep  and permanent creep  was  that  considered  of  of  was  observed  creep  two k i n d s ,  determined because  lateral  recovery,  r e a d i l y be  recovered.  into  percentage  set  9.  t i m e when no more m e a s u r a b l e From  as  permanent  of  was the  test.  Conclusions The more are  as  important conclusions  follows:  in this  investigation  1. C r e e p , b o t h l o n g i t u d i n a l a n d l a t e r a l , s p e c i m e n s was,  i n the  green  i n g e n e r a l , more m a r k e d t h a n i n e i t h e r  intermediate or a i r - d r y  condition.  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 o f t h e a i r - d r y mens.  Creep,  walls.  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 w e r e due 3.  speci-  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  presence of moisture i n the c e l l 2.  the  to moisture present i n the c e l l  conditions  walls.  Values of the c o e f f i c i e n t of l a t e r a l deformation, ^( 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  A{-~r?—:  l o a d r i s e are e n t i r e l y d i f f e r e n t from those d u r i n g the p e r i o d of creep, i n d i c a t i n g t h a t the c o r r e s p o n d i n g tions are e n t i r e l y different".  T h e i n  the  tangential  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 direction.  T h i s I s p r o b a b l y due  ning r a d i a l l y tion i n that 4.  deforma-  radial  to the medullary rays run-  i n t h e wood w h i c h somehow r e s t r i c t . i t s  deforma-  direction.  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  during loading at successively higher stress  observed  levels.  5. S t r e s s - s t r a i n c u r v e s f r o m 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 a n d g r e e n s p e c i m e n s w e r e f o u n d t o be- c u r v i l i n e a r 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 very  from  not  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 creep t h a t  d e v e l o p e d was  ultimately recovered i n a l l  had  the specimens  tested.  45 LITERATURE CITED  1. Australian Forest Products Laboratory. 1 9 5 5 - 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 i n 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: i n i t i a l l y 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  T a b l e 8 - VALUES FROM F I N A L STATIC TESTS IN COMPRESSION PARALLEL TO GRAIN FOLLOWING CREEP-RECOVERY TESTS.  Specimen  Moisture Content  Speciflo Gravity  i%) 0-1-1 oven-dry CA-1-6* 9.6 9.6 A-l-5 10.2 A-l-7 A-l-4 9.3 9.6 A-l-3 CM-1-1* 19.9 M-l-2 20o8 M-l-9 20.3 21.8 M-l-3 M-l-10 20.0 M-l-4 20.0 CG-1-10* 63.0 G-l-9 46.9 G-l-5 60.5 G-l-3 65.5 G-l-6 62.1 57.4 G-l-7  0.472 0.497 0.504 0.541 0.492 0.492 0.491 0.491 0.518 0.490 0.541 0.500 0.547 0.545 0.498 0.504 0.499 0.547  Max. Max. Stress Strain  Modulus of Elasti(mlcrocity ( p s i . ) i n . / i n J (lOOOpsj)  1L400 7300 7860 7760 7750 7600 4190 4400 3720 4400 4850 4180 4100 3290 3280 3320 3250 3900  12200 6000 7300 13,050 6700 6200 4400 4800 4720 5500 7900 • 4650 3850 4300 6240 4250 6600 4850  C o n t r o l specimens-were n o t s u b j e o t e d  Poisson's Ratio  1890  0.372  0.402  1610  0.210  0.596  2000  0.342  0.651  to creep-recovery  tests.  51  T a b l e 9- PERMANENT SET AND STRAIN RECOVERY OF DOUGLAS-FIR TESTED FOR CREEP  -  .  P e r Specimen  S e t  Strain  s  Radial Tangential Longitudinal (micro-inches p e r lnoh)  Recovery  Percentage of Axial Creep  0 - 1 - 1  0  17  270  5 1 . 8  A-1-5  48  77  300  7 0 . 4  A-1-7  48  91  A-1-4  «  A-l-3(a) (b) (c) M-1-2  *  # -27  M-1-9  0  370  5 3 c *  270  •:..56.5  «  0  1 0 0 . 0  10  40  8 7 . 3  232  7 0 0  55o5  •  80  8 3 . 5  - 1 6  7 5 0  7 7 . 7  490  7 9 o 9  M-1-3  -27  M-l-10  138  2 9  1440  6 4 . 6  M-l-4(a) (b) M-l-7(a) (b)  - 3 2  43  100  6 0 . 6  - 3 2 *  40  160  - 6  50  34  9 0 . 6  - 3 0  - 1 9 «  80  G-1-9  220  8 2 . 1  G-1-5  60  - 3 5  800  7 6 o7  G-1-3  - 2 2  - 2 0  175  8 9 o 4  0.-1-6  -67 ft  - 2 9 «  460  8 7 oO  60  180  0-1-7(a)  (b)  *  m a n e n t  -127  81o9 78o2  8 9 » 3  30  No v a l u e s r e c o r d e d due t o a c c i d e n t a l the l a t e r a l deformation apparatus. (a) V a l u e s o f 1 s t . c y c l e . (b) V a l u e s o f 2 n d . c y c l e . (c) Values o f 3 r d . c y c l e .  8 8 . 8  i disturbance of  TAMGEMTl  Fi'9.1-TEST  A L  SPECIMEN  Y  O C  -YrL  UPPER ARM  - - ^ L i  CORE  U P P E R GAUGE RIV6  SPECIMEN  FRAME  COIL  A  LOWER ARM  4_ f  LH5 ^ + 5  B,  L O W E R G A U G E RING J  r I  BASE  t  Fig.2-DIAGRAM OF COMPRESSOMETER  W  i  t A Section. X ~ X  6  Fig.3 - LATERAL  DEFORMATION  APPARATUS  ATTACHED  TO THE RADIAL SIDES  MEASURE  TAN/GEN/TIAL  TO  DEFORMATION/  2°  Fig. 4 - METHOD OF CUTTING MOISTURE SAMPLE FOR DETERMINATION/ OF SHELL AN/D CORE MOISTURE  DISTRIBUTION  H—  -  •  •  i  —  I  i 1  1  $  -  ft 11J  1 Q. Mi Til  - T  -- --  i•  1  j i.  t£. 1 I P  J  ,0  rI  LLLI.  i  I 1  I  1 1 j .'i  j .. .  *  bis  -  JJ  i  i  1 —,  ?l i:  s  I ES  \ i 1 BEE P - 11A E RE . A T I O V S 1P AT JIFF E R E WT S RESS T t T I T L1 l T •LLJ.L. 1 l• .LLQJ.J.. j._ L E KE:L 'S SPEICIWEV .A.I.R- >RY 1 KU__QO_M P R I I L P A R A L l -E.L 1 1M J J1 J_ 1 1 T.i j _ _i. i . Li rT i i i u i LLfJ.JI TOTS l i l t l l . ; . . \ \ L T T T I I T T l i TT I J i-1_ . 1. 1 i.1.1.1 J J E 5W C 71J T .1-A 3A 5_ _ P . R E i T oF 1 1 ORVJ5 JElvG" • i f ' T r ) ' | T } sm 4 I "T j :iC t _ J A S - IP i: RC &W_TAG-E f| pjOT-A L El\ £E;L ,s: 1 ! 1 • t i 13P % • i t i_  A x IA  —  --  -!  |  —  -  -•  -  *  c  jaws [ff  TfiWfF : ±b  T  1  1  c  |  ftsJ_  -  00  1 . 1 .  I-  .I *  j  1  q-th  7  I  1  1  7  —  1" 1  !  1  — 1 —  i  t  j  -  1  _].  1 1 I  -  -ill 1  -_1—! l i b ! -1 -  ...  -  rr  7  ______  |  -•  ]  1  i  *I  -  -  •5  —  i  ...  -» ^ H ~  DJ u  1  1 -  1 1  J-  -  -jU V  -  1  •  -  j  -  *  —  --  --  /- --  --  -  1 l  _1  —  --  1  1 II 1 1  -  i>7.  0-  JO.  ME WE:  8 3 Iff. A i r 1  us:  :n:  1 •  U U  TTT"T  _. '1 J.TJ11 I !  1  isjri:RA.);iv_4^  REDAT  AXE:  MltyOXE.S:  20  ICWSWIP. 1.1  30.  STRESS  SRECI8'ER_  TUt- . r  STREI  m  :dszip' ^CiTlOAE  -LU  SHOWN*  C R O S f-.LU-.U-i c j l l vs: itttt  E A C H LLPARTtCULAR  .1 T I.  MSXTPE'REi ! 1 s:tRr«S-TLWt  :; S T R E S S *  ELASTIC  %  -  - —-  . 1 ft |  1  ! 1  -  •_ -  -  1— ! 1  I,  _LL_ j_LJJ.. i i' i  --  -  ;  -  i  --  f  1 i  -  i  1  ! 1  i J_  -  1  I  1  -  -  I j  1  -  --  "r  -  -  -  1  i i  i  —  -  -  Mr •*  -  7 1l  *0  -:< i*  V) _'oJ_-A 0 -U -iii  —«x*  -  y I U. 0 i i  -  -  1 0 •3 i i.  i  -  \  1  r >  -|r  \  R  -  1  1  •  r  1  9-  1  ziyxp  T _  -  1 I i:M E__:i  -v- r :c  1 1  ..1, 1 1 -  -  > 1  . 1..:  e  -  ri  —  —  ji  ... j  jr : i i • II  -  •  •1  i  m  -  -  l  i  •F MII I1j  i" 1- 5  -  :  1 E tTIMf li ATTC /; > P :i P Aa 1 L E r. E E i: il 11 1 . J T LJ....T RE i ii l I • Mill \k R E S S TVTELVE.LS GREE SPEC M E M GQMT i l l .1 1 1 1i I'. 1_ i I i i LST.EP T f r i P A R m :iLE. D lAlAtl SXEEr E R E SSTOls T 1 IJ _i Trnj ii i i I J X i l IT i LAKE. S I . W R A S T t S S L I E V E-L\ S 1 i n n i T T r R ¥ J _ i l_ J.T CO : r L / U J _ c•i' i i Ii ir i-.i f ff- J Sl f t¥ i i n 1 TT M RT Tit i Fri T1 1 T1 I • r 1 ...LL k rREEP T S J R Avrs/ :CEh/_TASE . [ A L T iLAST;I.S_ I l l J M i I M M M 1 .1 1 1 ! 1 • > J.-JJJI I I 1i i i J :. 1. ±E&g.UG.lb.LAR STR.E3i§LTL"Ey.E.L, A  $  1  1  4,0  1  JJ.. 1  -  |  1 —-  -  f' 1  4  f  -  —  V  -  —  -i  ~  —1i  1 |  1 |  *-t— —_  --- -  1'  1 _ 1  -  --  •0 -  -  _  1  -  ...  --  ""Hr V) T  .._  -  -. . .  1 .1  1J  JrJJ -tu - b-U  1/  1  6I-  f. ii  /T )  J|  -!--  --  1  -  •A  1  -  /  1  ]L  I  r j.~i -L.  -  If 1  • 1  -L- 1 \ 44_  1  1 _  Jr_i - a _7i  .  1  1  I0  4-  1 1 j  i  1T 1 O 1 r TI  CR  1 l1  sT  1 I.1.1 O R E EIP L  S I R  LL .El TiRAlNL 1 ? 111 r LL  hjiEI  MEi1  E.  SHOWN/ T?fl1 KG A  1 1  -  0  1  1  •T MLlE S  1 J.i . J L r; DL.FIW T R E -AT.iOVSH.1 P j STRESS [ II I II i 1 1. I M I r 1. i r 1 1. i c GREEK/ C O W >RESSIOK/ 'SRBGrMEK/ :J_ 1 M' Q M L" E J P ARA 1 1 1 1 Tl T r N 1 (. 1 ILQAD G Rj A I N ' 1 BYF~< 1 . M I 11 T3 ' 1 -J I 1 J I I I . _L. - 1 r i-i RCENC 0 1: 1 n . I T 1"' n 1 .1. 1. T.  _AX t i l l . S_ T T V E AL  -  . •  Gl t  •  <  1. l '•: 1"  /Ct—•  T .  1.  :PE  JJ  m  _A  TAGE.  J :-_VG_I_IJ.AJ.LL1  F  .....  1U  J.J  1  IT  1 AS: :PE <_ LC EI .N. J/ T11A.1 -. *. t.- O F Li 1 1_ IVJ : k k C M 1 ?t ITO: PAR 1 C U 11 1 1T T T i n ' i 11 1 LMA i r ij '| .  LCOIAL. ! i 111 1 1  r1  1i  i  —  _ E L A S 1 _LG_ UJ u.  -_ 1  1  R  II  I I -II 1  -  -  t  Table 1 - SCHEDULE OP STEP-BY-STEP LOADING-UNLOADING TESTS (AIR-DRY CONDITION) Load Level 4 kips Per cent of max. load 13 of c o n t r o l s Specimen A-1-5 A-1-7 A-1-4 A-l-3(a) (b) (c)  L 8  0 12  A 16  D 18  26  39  52  59  I. N G 20 22 72  65  24 2fi  U ] L 0 A D I. N Gs 20 16 12 8 4 0  78 91  65 52 39 26 13  0  Time duration of sustained load a t each ILoad l e v e l i n minutes 20 5 5 5 225 5 5 5 20 330 20 5 15 15 15 5 5 5 15 180 1510 1500 5 5 5 5 5 15 3095 5 30 5 25 30 135 25 5 15 25 35 5 15 35 195 5 15 15 15 5 5 5 5 5 10 135 15  5  Table 2 - SCHEDULE OF STEP-BY-STEP LOADING.-UNLOADING TESTS (INTERMEDIATE CONDITION) L  Load Level kips 4 Per cent of max. load 24 of controls Specimen M-1-2 M-1-9 M-1-3 M-l-10 M-l-4(a) (b) M-l-7(a) (b)  8  0  48  A 10  D  60  72  12  :[  15  N  16"  U N ]_ 0 A 8 4  96  48  G.  89  D  I N G 0  24  0  Time duration of sustained l o a d at each load ILevel i n minutes 60 60 215 5 5 10 145 5 75 5 5 20 30 10 155 . 5 15 1040 10 20 1250 5 5 30 10 75 5 60 10 150 5 5 5 30 10 70 5 5 30 5 • 10 115 5 5  5 5 5 5 5 5 5 5  Table 3 - SCHEDULE OF STEP-BY«STEP LOADING-UNLOADING.TESTS (GREEN CONDITION) Load Level klpsj j Per cent of max. load of c o n t r o l s Specimen G-1-9  G-1-5 G-1-3 G>l-6  G-1-7U)  (b)  0 23  5 5 5 5 5 5  A 8 46  10  N 12  14  "ff  58  69  81  46  U TrX""0""A~"D I N G. 23  Time duration of sustained load a t each load l e v e l i n minutes 10 5 20 15 25 25  962 20 30 25  25  10  5  id"-  5 5  . 10 25  (a) 1 s t . 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 .  15  5  10 20 5 15 10 10  75 1025 90 135 95 150  j  :|  Table 4-  0 R E E P ; D/A T A  f OR  :  I  ^  -  I N  E P - B'' Y - S T E P  ST  M  ;  A  N N E  S U C::C;E S S I ; V . E . L I  A T  R;;  —  5  5  : 2020  (18*)* 1940  A-1-5  1920 (25*) 970 (12*)  A-l-4;  10  5  (25*)  A-l-7  1000  (23*) 950  (24*)  (b)  50  ; 5' j ,  :  ;  ; ;  ••'I; ' 5  (20%)  ..-: Ms;  1000  5  20  1000  5  0  (30*) 1000  G-l-6  30  (31*)  G-l-7(a)  20 0  (31*)  G-l-3  950  (24*)  :  ;  • •; 5 •  20  • ':.5. •;.  30  :  i  15  15. (45*) 1900  0; •  ........ • o; o; -3  3' • j  13 ; o  1900 (39*)  .  (48*)  1900  :\  -3 0  o  -10  -  ;  •  •  -17  5  50  10  65  -13  1 .'. "..  :  : 3000: (68*)  13  3 7  0  2850  (76%)  7  • 3000  (68^)-  : 24  :  :  • -.5 ; •  25 50  5  1900  (57%) 2000  (61%) 2000 (60%)  2000  (61%)  1900  (48?.)  • 20  50  •; 3 3  ;  40  10  •  • -3;.;.  6  -6  5  75  -13  -10  20  90  -19  -24  -30  -35  15 . 25 25  150  140  -41  135  .-25  0 : 0  •\ 2500 (60%)  '"2860" (61%)  15  ^Negative  sign  expressed  as p e r c e n t a g e ^ o f  specimen's  i n d i c a t e s n e g a t i v e creep which  (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 ) V a l u e s f o r 3rd. c y c l e o f l o a d i n g .  actual  crushing  I s o p p o s i t e t o bulging*'.  strength.  " "  0:  0  70  •• • S\.  ho  •:• 9r \  (76%)  • 2500 (75*)  ! 2500  "(76*)-  • 2380  (60*):.  7 :  10  ; 60  330  • -24  5  150  37:  38  ; -6; •'  -7  30  270  : : 30  35  ;  .  •;-57;:-  7  .' . 4or:.:  185  : 18 . . 10.  10  1190  -150  962  3330  -124  20  200  30  530  25  120  25 •  75  13 74  -10  :  5050  (44^) 4850 (62*) 4800  90  :20  120  19  20  175  32  60  25  3  7  •  (62*) 3890 (50*)  ' : 5  4860 (64*)  •:35-  ;  ;i5:  •••• - 6 4 ' '  ;, :  -34  r  :  -38;  : -iiJ! :  140  25  34  50;  9  13  3560  75  (95%)  4000  :10' •  (91%)  2320  67  -38  2035:;  83  353  387Q  309  232  6060  (53*) = 5820  (74*) 5  7  7  0  (74*) 4360 (56*)  H  I G/H E R  S T R E S S  65  180  225  810  ;15  445  95  161  250  51  77  5340 (69*)  67  6800 (88*)  1510  3 137  15  270  63  3330  15  1100  -41  6 155  '  3570 (73*)  1015 :60 ;  300 (72*)  .  30 :  -64  760 .  3570  :  .....;  . ..  ......  ..  ;  ; 276  ..  124  730  71  -70  -218  -94  -220  :  -38  3000  ;io  1350  3000  :io  2820  (90*) (92%)  ; -13 2860  .  -25 ' :•  ;275  :  -45  :  -47  E VE  L S  J  ;5830  (77*)  L  5th, S t t e . 6th Duration Stress D u r a t i o n of Longi- dRadlal Tangenof Level Sustained tudinal tial Sustained Stress Stress (minutes) ( m i c r o - i n c h e s p e r Inch) ( p s i . ) ( m i n u t e s )  -251  -29 :  •  6  ;  ;  :  :  •  :20  (76*)  :  ;  00  35  ; -45  :  170  : 30  ;  :  80  „  Stress.level  ..  55':;  ?\ 2860 -(86*)2500  20 3=  80  i 2860 • •; 5 (5%)  • 6; '  30  ;  10  7  85  • • ;15  ;  -54  #  . . 65  1  0  45  :  150  5  5  0  60  .5 .  30  1-2910 ;: 5 '. (38*) ... . - ! 3880 \ 25 . (51%) 7 • 25; 0  6  80  (50%)  •  0 *.  6  4  5  2000  (40*)  pi  -6;  (45*)  50 '. . 5';.  20  2000  6  .... ; ..  :-• 0  (51*)  3  ;  :  •: V  2000  -3  •• -3'r  40  :  (28*)  G-l-5  "  :5  950  G-l-9  25  20  950:  M-l-7(a)  •  (38*)  0  10  ; 3880  (49*) ' 3840  7  0  60  4040  3  0  ; 15  :  I r  0  3  90. :  .5 • •  (25*) 2910  0  ;• 0 : .•  40 *  _...  -3 •  20  . i5  1000  15;  :. 3 ; cr  0  20  1940  . . .• - ; . .0  30. :.  5  (25*)  ; (b)  3:'  (27#) 2910 (37*} 2880 (37*)  0  :| ' 5  (23%) 950  (19%) M - l - 4 ( a ) 1000  o  10  5  3030  0  "20  5  .1  M-l-10  0  ;.:.o!..  :  ' = ": ;'  :  . • : .; ' •. o'  j ::30 :. :  "••"•UJ  M-l-3  0  o ..  io-  ;.'('!))  M-l-Q  .  0  " i5  {26%)  M-l-2  0  20  A~l-3(a) 1940  :  —  L O A D E D  • 1st . iS-"t e p • S' t e p : 3rd . S t e p : 4th. ' 2nd f s : t &~x> S t r e s s D u r a t i o n Stress Duration 3 R E; E . ? V StressHDuration G R E E : • C2 K E E P -:~ --( Stress Stress D u r a t i o n 8 C R E E P Level Tangen-: L e v e l Longi- .'.->of-- • •L o n g i - R a d i a l R a d i a l ' 3T a n g en f L e v e l of. of LongiRadial Tangen- L e v e l of Radial LongiTangen- L e v e l Sustained t u d i n a l . tial Sustained t u d i n a l tial ; : Sustained tudinal tial Sustained tudinal tial Stress Stress i Stress Stress ( p s i . 5 ( m i n u t e s ) ( m i c r o - . .nches p<5 r i n c h ) ( p a l . ) ( m i n u t e s ) ( m i c r o - .nches pe.r Inch) ( p s i . ) ( m i n u t e s ) ( m i c r o - ! . n c h e s p e r i n c h ) ( p s i , ) ( m i n u t e s ) ( m i c r o - i n c h e s p e r i n c h ) ( p s i . )  Specimen  0-1-1  T  D;OUG L A S - F I R  «.44  7070 (62*)  40  1500  S t e p C R E E P LongiRadial Tangen-: tudinal tial ( m i c r o - * i n c h e s p e r Inch) 240  300  1140  89  91  267  336  F 0 R D O U G D A T A 1st. S t e D . 2nd S t r e s s D u r a t i o n Stress: Duration 1 R E G 0 V E R Y of • Tangen-: L e v e l Specimen L e v e l of 1 Longi- R a d i a l Sustained Sustained tudinal tial Stress Stress ( m inutes) ( p s i . ) ( m i n u t e s ) | ( m i c r o - '.nches p e r i n c h ) ( p s i . ) Table  0-1-1  5050., (44*)*  3880 (49*)  A-1-5  3840  A-1-7  (50*)  A-1-4  3890 (50*) A-1-3U) 1940  (b) (c)  M-1-2 M-1-9 M-1-3 M-l-10 M-l-4(a)  (b) M-l-7(a)  (b)  {26%) 2910  G-1-5 G-3-3  20  5  (38*)  4860  0  2000 (45*) 1900 (51*) 2000 (45*) 1900 (39*) 1000  5  ; 50  30  0  25  0  0  20 25  5  20  5  170  5  195  10  185  3 6 0 20  0  10 10 0  10 10 6  44 6  -3  57 3  2000  5  25.  0  7  1900  5  15  0  0  1900  5  120  3  (48*)  (40*) (40*)  1900  level  6  5  55  16  -  20  350  -47  10  5  55  0  5  95  -7  50  10""  950  (24*)  5  4040  1  100  (3&*)  :5  ;:  . .v.; 5 ; 5'i  2910 (38*) 970 (13*) 1940  •  30 • 15. •  0  40  13:  1  5  •  10  -12 -22  12  0  10 17  950 {19%)  0 {0%)  1000  (24*)  950 (20*) 950 950  5  30  10  400  ' i  (31*)  0  indicates negative recoveryfoulging) 1st. c y c l e o f u n l o a d i n g . 2nd. c y c l e o f u n l o a d i n g . 3rd. c y c l e o f u n l o a d i n g .  0 :  0  17  530  34  10 • 10 : 1025: ;  -  ; '..15 ;  95  ;80  105 > r  " 13.  180  10  260  13  900  -232  200  2  7  50  13  17  5  •. •  100  25 • '  -40  10  -10 ; 3  10  10  3  17 32  0  145  700  0  155;•;  1 0 ;(o*) i •• 0 •  1250  -16  #  1050  27  32  1520  60  64  i  t : .  -  •  84  70  . 25  17  6  115  165  37  54  0  {0%) 0  75  0  , 85 ;  Hoi) :  0  :  ..  -12  150  1  .  390  0  (0*)  0 (0*)  ; -22.  10  '." 13  27  {0%)  _Q •  . 3  170  ' 25  v  7  215  •'' 3  . . 3, .  0  50  ;  i •  ; •  0  5  (OJ.)  0  50  2910 (38*) 0  44  25  450  :  (o*)  140  10 •'  •• 5  \  0;  20  10 ."•  ; 5"': : •  1940 ": 5 (25*) : 0 • '135;'' : (0*) 970 • 35  : 3  3  20 • 75  5  (25/10  3  io'  :  0  (25*) 1920  6  A T ; , S UC C.;ESS I V / E L • ' 4th. S t e p J. • *R""ff o . o . v ' k Stress "Stress Duration LongiRadial Tangen- L e v e l of LongiTangen- L e v e l Radial tudinal tial Sustained tudinal tial Stress ( m i c r o - .nches p<ar i n c h ) ( p s i . ) ( m i n u t e s ) ( m i c r o - I n c h e s p e r i n c h ) ( p s i , ) 0  (13*)  400  {0%)  950  3  S T E P - B Y - S .1.. E P s t  5  1940  ; 10  0.  15  {0%)  1000 (30*) 1000  3030 (27*)  ."•7  . 6  {20%)  (28?.) 0  0  :  30  ...  !  -  ..,  "115. '. ;  295  -29  600  -29  3  540  -67  -29  430  -38  • (0*) ;' :  10  (24*)  e x p r e s s e d as p e r c e n t a g e o f s p e c i m e n ' a a c t u a l c r u s h i n g  ^Negative s i g n (a) V a l u e s f o r (b) V a l u e s f o r (c) Values f o r  50  0  {23%)  950 (25*) 1000  0  1  •  (26*)  3880 (51*) 1000  0  5  (35*) 2910 2880  - F.;: I R U N L 0 A D E D I N . S t e p R E G-0 V E R Y Stress Duration LongiR a d i a l ; Tangen- L e v e l of ; tudinal tial Sustained Stress ( m i c r o - ! Inches p e r i n c h ) ( p s i . ) ( m i n u t e s ) L A S  {23%)  0  (48*) Stress  13  50  2000  (b)  0  10""  (24*)  {61%)  G-l-7(a)  .  5  {60%)  G-l-6  0  {37%)  5  (64*)  0  5  5  1900 (57*) 1000 (31*) 2000  G-1-9  5- R E C 0 V E R Y  350  -32 :  strength.  17  1  0  (o*)  150  34  M A  N.N.E-.R:  :  1  2020 (18?.) 970 (12*) 960 (12*) 970 (12*)  0 (0*) 1940  {26%)  5  10  20  100  15  15  75 60  0 * .-10;'' ' '  19  0  1010  0  ;  30  LOW 5th Duration  0  E R  10  St e p ::  20  {0%) •  0  s. s  L E V E L S  0  0  0  230  10  135  245  {0%)  330  205  41  44  150  175  25 ;  17  3095  180  10  60  0  54  {0%) 0  S T R iE  ' 6th. S t e p S t r e s s D u r a t ion fl R E G 0 V E R If* R E d . 6 \1 ZTT Radial Tangen- L e v e l of Longiof || L o n g I - J R a d i a l tial Sustained tudinal Sustained!tudlnal Stress Stress ( m i n u t e s ) ( m i c r o - I n c h e s p e r i n c h ) ( p s i . ) (minutes)II ( m i c r o - : :  9%)  (  30 10  Y  10%)  195  45;  6  5  80  . 0.  7 23  970  {13%)  , 10  165  0 {0%)  81  TaMe  Specimen  6  - MODULUS OF ELASTICITI AND COEFFICIENTS;  S t e P i 2nd. S t e ,_P_ • C e e f f i c i e n t of L a t e r a l C o e f f i c i e n t o f L a t e r a l Modulus Deformation of Deformation During During During Elasticity During Loading Creep Loading ; Creep  1st.  Modulus of  Elasticity (1000 p s i . )  M*  M  Mr  T  0-1-1  1800  A-1-5  2110  .175  .305  0  0  A-l-7  1690  .349  .448  0  A-l-4  2060  .528  .336  0  . .  0.232 0.406 0.000 0.000  :  .  A-l-3(a)  -  2200  (b)  2020 :  (o)  1900  OF  .995  '.  -  .  .600  0:  1800  psij  M  A  M  M«  r  Modulus of  Elasticity  M  3rd. S t e P C o e f f i c i e n t of Deformation  (1000 p s i )  r  0.211 0.486 0.000 0.000  1740  During  A  M  Lateral  M*  T  IN STEP-BY-STEP  1  During Creep  Loading  M  LOADING  -•  Modulus of Elasticity  Mr  0.186 0.490 0.000 0.000  S t e p •4thJ C o e f f i c i e n t of  :Def ormatidn  During Loading  SUCCESSIVELY HIGHER STRESS,-LEVELS  AT.  Lateral  . During , Creep  M#  Mr  (1000 p s i } 1710  MANNER  M  r  0.176 0.448 0.000 0.067  5th. S t e P Modulus :Coeffc±ent oi: L a t e r a l Def ormal: i o n of During Elasticity ; During Loading Creep  M  (1000 p s i )  T  1710  0.229  M«  Mr  0.458 0.017 0.033  Modulus  :  Of  Elasticity  (1000 p s i ) 1710  .150  1940  .236  .362  .133  .156  1870  .227  .394  ;.i58  .167  1850  .278  .410  .169  .191  ••0;'  1780  .359  .481  •• 0  •; .078  1720  .352  .486  .071  .236  1720  7-363  .493  : .183  .343  1720  .432  .544  .214  .362  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  ;  1940  .183  .456  : 0  0  1870  .248  .485 . • o; '  ; 0.  1940  .178  .450  .120  / .140  1940  .236  .450  i .100  1940  .248  .456  .179  .243  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  1670  .479  .525  -.113  -.360  1540  .415  .470 -.073  -.136  .246  o  .': .100  .086  >  .530  .625  M-l-9  1790  .444  .912 -.150 -.150  1500  .330  .661  H200  .260  1460  .331  .626  .254  1400  .310  .592  .029 -.016  M-l-3  1600  .391  .444  .060  1480  .256  .388  .038  .082  1490  .253  .387 -.022 -.022  1470  .215  .328  .041  .179  M-l-10  1900  .539  .808  .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  ; .293 .446 -.084  .364  1980  .775  .665  0  [ 0;;  1670  • 75  .491  .120  -,120  1670  .466  1980  .742  .621  o  0  1640  .466  .480  .060  .120  1610  .434  G-l-9  1420  .461  1400  .342  _  -  1240  .252  G-l-5  1560  -.150  1330  .234  .482 -.173 -.133  1390  G-l-3  • - M-i-yia) (b)  ;  ;* o:  ! . . .  0  4  :  -.150  ;  .482  .216  .463  .109  .  -.126  .158  .450  -.037  -  -.200 ;  .097  :  .182  1  1600  1520  .451  •  .475  : .097 .170 •  -.076  .275  .710 -.150  1850  .338  .618  0  ; o .  1670  .282  .598 -.211 -.267  1470  .309  .494  - .145 -.170  1430  .237  .444  G-l-6  1820  .360  .828  0  1540  .228  .440 -.200 -.233  1350  .227  .354 -.121 -.072  1280  .208  .344 -.033 -.078  G-l-7(a)  2210  .736  -  -.333  - . 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  (a) Values f o r 1 s t . c y c l e o f l o a d i n g . ( b ) Values f o r 2nd.:cycle o f l o a d i n g . ( c ) Values f o r ; 3 r d . c y c l e o f l o a d i n g .  0.285 0.442 0.012 0.025  .150  1750  .075  Mr  .339  M-l-2  0  M«  .196  •  0  6th. S t e p C o e f f i c i e n t of Lateral Deformation During During Creep Loading  1980  :  .819 .208  (1000  LATERAL,DEFORMATION DURING-  -.052  -.164  -.161  -.171  1700  1  .260  .470 -.037 -.040  T a b l e 7'- MODULUS OF ELASTICITY AND COEFFICIENTS  Specimen  Modulus of Elasticity (1000 ps  1  2nd. S t e p C o e f f i c i e n t of L a t e r a l L a t e r a l : Modulus of peformal :ion p e f o r m a t -ion Dui ' i n g Elasticity Dur1 .ng Dur 'ing Lng : Fur3 RecoTi rery Recc >very Unlos L d i n g Unlos id i n g  S t e P „st. | C o e f f i c i e n t of  1.)  M*  M  r  M#  0.264 0.464 0.000  O-lrl  1800  A-l-5  1580  .163  .302  A-l-7  1780..  .291  .384  A-l-4  1910  .328  .382  A-l-3(a)  1880  .292  .745  (b)  1800:,  .301  .652  .150  (c)  1800  .280  .602  .240  :  M  (1000  r  0.000  1710  0 .260  0 0  psi)  MM  Mr  0.188 0.443  M«  Mr  0.000 0.000: : 0 .140  1900  .194  .369  : .200  1850  .405  .575 . ^.325  ;.333  1900  .320  .341  o  1940  .241  .450  1830  .621  .650  :.600  1800  .264  .429  ; .100  .500  \ 0  :  .0  .  '; 0  .314  . .536  .118  .259  .297  .505  :.042  .200  M-l-3  1350  .382  .424  0  ; 1190  .038  1370:'  .242  .368  .025  .025  M-l-10  1590  .480  .532 -.016  .308  1490  .494  .646  .064  .198  M~l-4(a)  1600  .424  .461  .260  1600  .300  .451  0  .150  0 0  1410  .341  .392  -.043  .314  0  1590  .424  .460  .520  .120  1440  .476  1270  .334  .496  .521  1490  .490  .502  .025  G-l-9  1150  .386  - _  .291  G-l-5  1130  .211  .330 -.134  G-l-3  1390  .278  .401  0  G-l-6  1220  .182  . 292  -.074  G-l-7(a)  1500  .521  .564 -.240  .; .200  (b)  1360  .489  .560 -.220  .170  (b)  .050  , -  J .028  -  .056  i .050  .139  -  .041  .218 -.258  .024 .050  : .218  1370  .250  .416 -.045  To  1110  .135  .223 -.089 -.022  .400  .526 -.300  .300  .440  .520 -.092  .049  (a) V a l u e s f o r 1 s t . c y c l e  of;unloading.  (b) V a l u e s (c) V a l u e s  of unloading. of unloading.  f o r 2nd. c y c l e f o r 3rd. cycle  .492  ...  -  1560  M  r  M*  M  .356  0  • .280  1870  .330  .386  .0  * .241  .462  .030  ; .130  1870  .560  .432  .400  j .400  2040  .234  .445  .134  1830  .241  .423  .060  .; .294  1760  .240  .416  .159  ; .188  • . :  ! .023  •  1600  1250 »  .  0  .362  .461  .142  .244  .234  .360  .026  ; .030  .354  .382  .046  : .049  0  0.177 0.563  1770  • :  '  1540  -  .240  .421 -.031  .388  .467  * .463  .475  .240  LOWER STRESS LEVELS  5th. S t e P C o e f f i c i e n t of  Modulus of  Elasticity  1740  ;  Modulus : of  Lateral  Deformation  During Unloading  Mr  0.243 0.504  During Recovery  M*  M  Elasticity  0.000 0.000  1900  .318  .342  .164  •; .176  .400  1750  .420  .500  .143  .097  , .167  2060  .380  .392  .056  \ .333  :  1800  :• .251 .508  0  : .327  • , .  !  •  :>.''. '  w  ' . . . '.  -  t  \ .216  !  i i  !  .670 \ .240 I  -  .224 ! .327 \  -.098 !  -.129  -  .101  .262  -  .101  .110 -.124  ; .013 -.o54  : I  •  .346 ; .482  -.088 : .079  :  16600 ••  M  R  0.430 0.430  Ma 0^000  0.000  •  .155  . : 0 • .288  . ..  6th. t e n C o e f f i c i e n t of L a t e r a l Deformation During i During ' Unloading : Recovery  (1000 p s i )  r  •  .  1450  SUCCESSIVELY  (1000 p s i j  r  .253  0.000 0.000  •  .280  1640 ,  M-1-7U)  psi)  • 536  ••..233  1240  (1000  .410  .600  M-l-9  Mr  1850  2200  .100  Elasticity  : .340  0  .100  Of. :  .260  .343  ;  Modulus  —4 4th. S t e p C o e f f i c i e n t of L a t e r a l Reformation During Dui 'ing UnlO£idingRecovery,  .186  1870  .482  . 1  1900  .200  .384  •  .140  0.169 0.531  .500  1540  /. •  0.000. 0.000. .363 i i o o .300  1740  .376  «300  .452  M#  r  1750  0  .430  M  (1000 psi.)  .250  .542  1610  . ...  .349  .406  (b)  Elasticity  .194  1540  0  Modulus of  3rd. S t t e JP C o e f f i c i e n t of L a t e r a l Deformation During During Unloading Recovery  1900  M-l-2  ;  OF LATERAL DEFORMATION DURING. UNLOADING- IN STEP-BY-STEP MANNER AT  1  1800  .282  .542  .024  .331  Table  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 F O L L O W I N G C R E E P - R E C O V E R Y . ; T E S T S -  Moisture- S p e c i f i c Content Gravity Specimen:  GO 0-1-1 o v e n - d r y CA-1-6* 9*6 A-l-5 9.6 A-l-7 10.2 A-l-4 9«3 9.6 A-l-3 CM-1~1 . 1 9 . 9 M-l-2 20,8 M-l-9 20,3 21o8 M-l-3 M-l-10 20.0 M-l-4 20.0.. 63*0 G-l-9 46.9 G~l~5 60.5 G-l-3 65.5 G-l-6 62.1 57.4 G-l-7 #  od-i-io*  Max. Stress  Max. Modulus S t r a i n !• ' o f jElastifoicro1 city , ( p s i . ) i n y i n J ; ( l O O O p s 3)  0.472 1L400 7300 0.497 0.504 7860 Oo54l 7760 0 . 4 9 2 • 7750 0.492 7600 4190 0.491 4400 0.491 0.518 3720 0.490 4400 0.541 4850 0.500 4180 4100 0.547 3290 0.545 0.498 3280 0.504 3320 3250 0.499 3900 0.547  13200 6000 7300 13,050 6700 6200 4400 4800 4720 5500 7900 4650 3850 4300 6240 4250 6600 4850  CCOntrol 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  Poisson s Ratio 1  1890  i0.372 0.402  1610  0.210 O.596  2000  0.342 0.651  to creep-recovery  tests.  Table 9 - PERMANENT SET AND STRAIN RECOVERY OF DOUGLAS-FIR TESTED FOR CREEP  P e r . Specimen 0-1-1 A-1-5 A-1-7 A-1-4 A-3-3(a) (b) - (c) M-1-2 M-1-9 M-l»3 M-l-10  M-l-4(a) (b) M-l-7(a) (b) G-1-9 G-1-5 G-1-3 CE-1-6  G-l-7(a) (b)  m a n e n t  S e t  S t r a i n Recovery  R a d i a l Tangential Longitudinal Percentage of A x i a l Creep (micro-inches per inch) 0 48 48 &  a -27  0 -27 138 -32 -32 «•  34 -30 60 -22 -67 &  4*  17 77 91 10 232  *  -16 -127 29 43 40 -6 -19 -35 -20 -29 a  60  270 300 370 270 0 40  700  80 750 490 1440 100 160 50 80 220. 800 175 460 30 180  51.8 70.4 53.1 -56.5 100.0 87.3 55.5 83<.5 77.7 79.9 64.6 60.6 81.9 78.2 90.6  82.1 76.7 89.4 87.0 89.3 88.8  * No values recorded due t o a c c i d e n t a l disturbance 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 2 n d . c y c l e . '(c) Values of 3 r d . c y c l e .  Note: Pages 46-67 oversized and are containod i n aeeeapanying-  Library. UBC November 2nd, 1962.  see.  p-ij  

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