A Procedure to account for machine stiffness in uni-axial compression tests

Publisher’s version / Version de l'éditeur:

IAHR 7th International Symposium on Ice, Proceedings, 1, pp. 39-47, 1984

READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE.

https://nrc-publications.canada.ca/eng/copyright

Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la

première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n’arrivez

pas à les repérer, communiquez avec nous à [email protected].

Questions? Contact the NRC Publications Archive team at

[email protected]. If you wish to email the authors directly, please see the

first page of the publication for their contact information.

NRC Publications Archive

Archives des publications du CNRC

This publication could be one of several versions: author’s original, accepted manuscript or the publisher’s version. /

La version de cette publication peut être l’une des suivantes : la version prépublication de l’auteur, la version

acceptée du manuscrit ou la version de l’éditeur.

Access and use of this website and the material on it are subject to the Terms and Conditions set forth at

A Procedure to account for machine stiffness in uni-axial compression

tests

Timco, G. W.; Frederking, R. M. W.

https://publications-cnrc.canada.ca/fra/droits

L’accès à ce site Web et l’utilisation de son contenu sont assujettis aux conditions présentées dans le site

LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D’UTILISER CE SITE WEB.

NRC Publications Record / Notice d'Archives des publications de CNRC:

https://nrc-publications.canada.ca/eng/view/object/?id=d8b7148a-0a29-41ef-8bc9-b37bcb113a44

https://publications-cnrc.canada.ca/fra/voir/objet/?id=d8b7148a-0a29-41ef-8bc9-b37bcb113a44

Ser

/

3

q&J-

N21d

National Resea&

Conseil

national

0.

1294

Division of

Division des

Building Research

recherches en batiment

A Procedure to Account for

Machine Stiffness in Uni-Axial

Compression Tests

by

G.W. Timco and R.M.W. Frederking

ANALYZED

Reprinted from

IAHR

7th

International Symposium on Ice

Hamburg, W. Germany, August 27 -31,1984

Proceedings. Vol. I. p. 39-47

(DBR Paper No. 1294)

Price $1.00

NRCC 24681

I1 est bien connu que la rigidit6 des machines d'essai peut

fausser les resultats des essais de compression uniaxiale de la

glace.

Cela provient du fait que les machines d'essai de

compression conventionnelles ne sont pas suffisanment plus

rigides que 116chantillon de glace soumis aux essais.

I1 en

resulte donc un processus complexe d'interaction entre la

machine et la glace.

Cette communication presente un modele

simple de ce processus et les equations deterninantes.

On

obtient ainsi une formule correctrice qui pernet de tenir

compte de la rigidite de la machine.

Le nodele est verifie

avec des echantillons de glace columnaire d'eau douce et de

glace granulaire d'eau de mer en conparant les valeurs des

resistances corrigees pour trois machines d'essai different&

avec celles obtenues en utilisant une machine d'essai

circuit

ferm6 de forte capacite.

LIHR

Ice Symposium

1984

Hamburg

A PROCEDURE TO ACCOUNT FOR MACHINE STIFFNESS

I N UNI-AXIRL CaMPRESSION TESTS

G. W. Timco and R. F r e d e r k i n g N a t i o n a l Research C o u n c i l Canada Research O f f i c e r s

ABSTRACT

I t

is

w e l l e s t a b l i s h e d t h a t t e s t machine s t i f f n e s s c a n i n f l u - e n c e t h e r e s u l t s i n u n i - a x i a l compression t e s t s on i c e . T h i s comes about because t h e c o n v e n t i o n a l compression machines a r e n o t s u b s t a n t i a l - l y s t i f f e r t h a n t h e p i e c e of i c e under t e s t ; hence t h e t e s t becomes a c o m p l i c a t e d i c e - s t r u c t u r e i n t e r a c t i o n p r o c e s s . I n t h i s n o t e , a s i m p l e model o f t h i s p r o c e s s is o u t l i n e d and t h e d e f i n i n g e q u a t i o n s a r e e s t a b - l i s h e d . T h i s y i e l d s a c o r r e c t i o n formula which a c c o u n t s f o r t h e s t i f f - n e s s o f t h e t e s t machine. The model is checked f o r both columnar f r e s h - water i c e and g r a n u l a r s e a i c e by comparing t h e c o r r e c t e d s t r e n g t h v a l u e s f o r t h r e e d i f f e r e n t t e s t machines w i t h t h o s e measured using a h i g h - c a p a c i t y c l o s e d - l o o p t e s t machine.

INTRODUCTION

I n r e c e n t g l a c i o l o g i c a l l i t e r a t u r e , t h e r e has been d i s c u s s i o n on t h e i n f l u e n c e of t h e t e s t machine s t i f f n e s s on t h e u n i - a x i a l compres- s i v e s t r e n g t h of i c e which has been measured using c o n s t a n t cross-head r a t e t e s t machines (Aaynes, 1979; Sinha and F r e d e r k i n g , 1979; S i n h a 1981a, 1981b. 1982; Frederking and Timco, 1983, 1984). B a s i c a l l y this problem a r i s e s because t h e s e c o n v e n t i o n a l t e s t machines a r e not c o n s i - d e r a b l y more r i g i d t h a n t h e i c e specimen being t e s t e d . Because o f t h i s , t h e t e s t machine i t s e l f can deform e l a s t i c a l l y a s i g n i f i c a n t amount d u r i n g t h e t e s t . T h i s deformation of t h e t e s t machine r e s u l t s i n a lower a p p l i e d s t r a i n r a t e on t h e sample t h a n t h e nominal s t r a i n r a t e . S i n c e t h e t e s t r e s u l t s a r e u s u a l l y i n t e r p r e t e d i n terms of t h e s t r a i n r a t e , and t h e compressive s t r e n g t h o f i c e is s t r a i n - r a t e dependent, t h i s l e a d s t o an i n a c c u r a t e i n t e r p r e t a t i o n of t h e t e s t . Thus, a t e s t o f i c e s t r e n g t h made on a machine which is not s i g n i f i c a n t l y more r i g i d t h a n t h e i c e sample w i l l r e s u l t i n a lower s t r e n g t h t h a n w u l d occur f o r a t r u e s t r a i n r a t e e q u a l t o t h e nominal r a t e . It has been shown, i n f a c t , t h a t f o r t h e same nominal s t r a i n r a t e , t h e a p p a r e n t s t r e n g t h of i c e i n c r e a s e s with i n c r e a s i n g t e s t system s t i f f n e s s ( S i n h a , 1981a).

To overcome t h i s problem, r e c e n t t e s t s of i c e s t r e n g t h have been performed on "closed-loop" t e s t machines. I n t h e s e t e s t s , t h e r a t e o f d e f o r m a t i o n o f t h e sample is measured and i n s t a n t a n e o u s l y fed back t o t h e c o n t r o l system. T h i s , i n t u r n , a d j u s t s t h e cross-head r a t e so a s t o m a i n t a i n a t r u e c o n s t a n t s t r a i n r a t e of t h e sample d u r i n g t h e t e s t . Using a t e s t machine of t h i s t y p e , it i s p o s s i b l e t o i n v e s t i g a t e t h e s t r e n g t h of i c e a s a f u n c t i o n of t r u e c o n s t a n t s t r a i n r a t e ; i.e. t h e i n f l u e n c e of t h e t e s t machine s t i f f n e s s

is

e l i m i n a t e d . In any s t u d y i n v e s t i g a t i n g t h e p h y s i c s o r mechanisms o f i c e f a i l u r e , a machine of t h i s type should be used, i f a t a l l p o s s i b l e . Closed-loop machines, however, have s e v e r a l drawbacks s i n c e t h e y a r e q u i t e expensive, w r y l a r g e and not e a s i l y d e p l o y a b l e for use i n t h e f i e l d . For many e n g i - n e e r i n g a p p l i c a t i o n s , t h e r e f o r e , a c o n v e n t i o n a l t e s t machine is used. Most of t h e i n f o r m a t i o n i n t h e l i t e r a t u r e An t h e s t r e n g t h o f i c e h a s been o b t a i n e d using such t e s t machines. I t w u l d be h i g h l y d e s i r a b l e , t h e r e f o r e , t o f i n d a t e c h n i q u e which would a l l o w a l l t h i s i n f o r m a t i o n t o be compared by e l i m i n a t i n g t h e i n f l u e n c e o f t h e machine s t i f f n e s s . T h i s t e c h n i q u e would a l s o f a c i l i t a t e f i e l d t e s t i n g s i n c e l i g h t e r and more

e a s i l y d e p l o y a b l e t e s t machines w u l d s t i l l g i v e r e s u l t s which c o u l d be i n t e r p r e t e d i n terms o f s t r a i n r a t e .

I n t h i s note, a simple model is p r e s e n t e d f o r t h e s t i f f n e s s o f a c o n v e n t i o n a l test machine. T h i s y i e l d s a c o r r e c t i o n formula which a c c o u n t s f o r t h e machine s t i f f n e s s . The model is checked by comparing s t r e n g t h v a l u e s which were o b t a i n e d f o r both columnar f r e s h w a t e r i c e and g r a n u l a r s e a i c e using t h r e e d i f f e r e n t t e s t machines and c o r r e c t e d using t h i s formula, with t h o s e measured using a high c a p a c i t y c l o s e d - l o o p machine.

DEFINING EQUATIONS

The model f o r t h e system o f an i c e sample i n a t e s t machine

is

shown i n F i g u r e 1. It c o n s i s t s o f a s e r i e s combination o f two i n d i v i d u - a l e l e m e n t s which r e p r e s e n t t h e machine s t i f f n e s s and t h e i c e s t i f f n e s s .

L a n n CELL- C O M P L I A N T c D E F L E C T I O N P L A T E N S L O A D I N G S Y S T E M E5

?

K,3 S P E C I M E N a1 L O A D I N G M A C H I N E b l T E S T S Y S T E M

FIGURE 1 SCHEMATIC OF ( a ) COMPRESSION W I N G MACHINE AND (b) EQUI VALENP STIFFNESS ELEMENTS

I t has p r e v i o u s l y been d i s c u s s e d by Frederking and Timco (1983). I n b r i e f , t h e l o a d i n g system s t i f f n e s s K i s is d e f i n e d a s

where AP is a load increment, 6j is t h e c o r r e s p o n d i n g d i s p l a c e m e n t increment o f t h e screw jack, and 6s is t h e r e s u l t i n g d e f o r m a t i o n increment o f t h e sample. 6, is d e f i n e d a s

where E is t h e e l a s t i c modulus of t h e specimen, 1 i s t h e l e n g t h and A its c r o s s - s e c t i o n a l a r e a . Combining t h e s e e q u a t i o n s and s e t t i n g t h e sample s t i f f n e s s Ks = EA/1, y i e l d s (per u n i t t i m e )

T h i s e x p r e s s i o n r e l a t e s t h e d i s p l a c e m e n t r a t e o f t h e sample (6,) t o t h e displacement r a t e of t h e cross-head o f t h e machine ( 6 j ) . S i n c e t h e r e s u l t s of compression t e s t s a r e u s u a l l y d i s c u s s e d i n terms o f t h e

. .

s t r a i n r a t e ( E ) o f t h e sample and E = 6/E, e q u a t i o n (3) y i e l d s a r e l a - t i o n s h i p between t h e s t r a i n r a t e i n t h e sample ( E s ) and t h e nominal s t r a i n r a t e o f t h e t e s t ( E n ) a s

T h i s e q u a t i o n shows t h a t t h e sample s t r a i n r a t e is l e s s t h a n t h e nominal s t r a i n r a t e , and t h a t a s t h e l o a d i n g system s t i f f n e s s becomes w r y l a r g e compared to t h e i c e s t i f f n e s s , Es approaches En, a s expected. To use t h i s e q u a t i o n , both t h e l o a d i n g system s t i f f n e s s and t h e i c e s t i f f n e s s must be known. The former is o b t a i n e d by l o a d i n g a specimen o f known c o n s t a n t e l a s t i c i t y and measuring t h e l o a d , movement of t h e screw jack, and l o a d frame d e f l e c t i o n ( F r e d e r k i n g and Timco, 1983). The r e s u l t s f o r t h r e e d i f f e r e n t t e s t machines which t h e a u t h o r s have used ( I n s t r o n , T T ~ - L , 0.1

w

c a p a c i t y ; ~ r i - t e s t 50, 0.06 MN c a p a c i t y ; S o i l t e s t CT-405, 0.05 W c a p a c i t y ) a r e shown i n F i g u r e 2. Note t h a t t h e machine s t i f f - ness is not a c o n s t a n t , but a f u n c t i o n of l o a d a t low l o a d s , and f o r a g i v e n t e s t machine, t h e s t i f f n e s s is g r e a t e r for s t e e l p l a t e n s t h a n for compliant p l a t e n s . For t h e a n a l y s i s i n t h i s paper, t h e l o a d dependence o f t h e machine s t i f f n e s s w i l l not be t a k e n i n t o account i n a r i g o r o u s f a s h i o n ; i n s t e a d , it is approximated a s t h e average v a l u e o f t h e machine s t i f f n e s s up to t h e l o a d l e v e l a t which t h e i c e y i e l d s . With r e g a r d t o t h e i c e s t i f f n e s s , t h i s is a l s o not a c o n s t a n t f o r t h e s e t e s t s s i n c e t h e specimen is loaded t o its y i e l d p o i n t . For low l o a d s , t h e i c e s t i f f n e s s is g i v e n by

EA/L

where E is t h e e l a s t i c modulus o f t h e i c e . With i n - c r e a s i n g l o a d , t h e i c e s t i f f n e s s d e c r e a s e s such t h a t , by d e f i n i t i o n , it is z e r o a t t h e y i e l d p i n t . S i m i l a r t o t h e machine s t i f f n e s s , t h i s l o a d

dependence w i l l not be t a k e n i n t o account i n a r i g o r o u s f a s h i o n ; in- s t e a d , t h e ice s t i f f n e s s is approximated a s t h e a v e r a g e of t h e i c e s t i f f n e s s d u r i n g t h e t e s t (assuming a l i n e a r d e c r e a s e with l o a d to

y i e l d ; i.e.

Ci

= EA/2I1 where E is t h e e l a s t i c m d u l u s of t h e i c e for low l o a d s ) . It s h o u l d be noted t h a t w i t h i n c r e a s i n g l o a d , t h e s t i f f n e s s o f t h e t e s t machine i n c r e a s e s whereas t h e s t i f f n e s s o f t h e i c e specimen d e c r e a s e s . Thus, t h e p r e s e n t approach g r e a t l y s i m p l i f i e s a complex i n t e r a c t i o n problem by using a v e r a g e v a l u e s i n a l i n e a r system t o r e p r e s e n t t h e s i t u a t i o n . With t h i s approximation, t h e r e a d e r

is

c a u t i o n e d not t o i n t e r p r e t n o t h e c o r r e c t e d s t r a i n r a t e - ES a s t h e t r u e s t r a i n r a t e 100 - - o f t h e t e s t . To v e r i f y t h e +

-

+ a l . ~ l s f f 1 I I I L PL**ENf) x - 8 0

-

IWEftlOY [ S T E E L PLhfZ"3l

-

a p p l i c a b i l i t y o f e q u a t i o n ( 4 )

,

it was used

to

c o r r e c t 1911. T F l T I t l l Y I & I * * l . L h I I Y I I s t r e n g t h measurements f o r two d i f f e r e n t c a s e s . F i r s t , £or measurements on columnar S2 f r e s h w a t e r i c e which were o 10 2 0 3 0 - 0 so so ro made using a c o n v e n t i o n a l L O A D I K N I machine with s t e e l p l a t e n s under c a r e f u l l y c o n t r o l l e d FIGURE 2 l a b o r a t o r y c o n d i t i o n s ; and

LOADING SYSTE4 STIFFNESS second, on g r a n u l a r s e a i c e WRSUS

LOAD

FOR THREE made i n t h e f i e l d using two COMPRESSICN TEST MACHINES d i f f e r e n t t e s t machines w i t h both s t e e l and c o m p l i a n t p l a t e n s . The c o r r e c t e d v a l u e s were compared t o t h e l a b o r a t o r y measurements on t h e same t y p e o f i c e using a c l o s e d - l o o p t e s t machine. I n both c a s e s , t h e t e s t d a t a was t a k e n from p r e v i o u s l y p u b l i s h e d t e s t r e s u l t s .

FRESEWATER ICE

The i n f o r m a t i o n on f r e s h w a t e r i c e was t a k e n from t h e p u b l i s h e d work o f Sinha (1981a) who compared t h e r e s u l t s o f compression t e s t s by s e v e r a l i n v e s t i g a t o r s using a number of t e s t machines. For t h i s

a n a l y s i s , t h e r e s u l t s o f h i s t e s t s u s i n g t h e c o n v e n t i o n a l I n s t r o n t e s t machine a r e compared t o h i s c l o s e d - l o o p t e s t r e s u l t s . These r e s u l t s were p r e s e n t e d i n t h e form o f a b e s t - f i t r e g r e s s i o n l i n e t h r o u g h h i s d a t a and t h e y a r e shown i n F i g u r e 3. I n o r d e r t o a p p l y e q u a t i o n (4) t o h i s r e s u l t s , t h e l o a d i n g system s t i f f n e s s and e l a s t i c m d u l u s o f t h e i c e must be known. The former is shown i n F i g u r e 2. An a p p r o p r i a t e v a l u e f o r t h e e l a s t i c m d u l u s o f t h e i c e f o r a g i v e n s t r a i n r a t e was t a k e n from t h e r e s u l t s of T r a e t t e b e r g e t a l . (1975) which g i v e s t h e s t r a i n r a t e dependence o f t h e m d u l u s f o r both g r a n u l a r and columnar S2 f r e s h - water i c e . Using t h e s e v a l u e s , t h e t e s t r e s u l t s o f S i n h a were re-analy- s e d u s i n g e q u a t i o n ( 4 ) , and t h e r e s u l t is shown i n F i g u r e 3. T h e r e is e x c e l l e n t agreement between t h e s t r e n g t h o b t a i n e d u s i n g t h e c o n v e n t i o n a l and t h e c l o s e d - l o o p machine. L A B O R A T O R Y T E S T S S T E E L P L A T E N S 1 o - ~ 10." l o - = S T R A I N R A T E ( s - ' )

FIGURE 3 STRENGTH-STRAIN RATE RELATIONSHIP FOR S2 FRESHWATER ICE SHOWING SINJiA'S RESULTS OBTAINED USING BOTH A CONVENTIONAL AND CLOSED-LOOP TEST MACHINE. THE DASHED LINE I S TBE CONVENTIONAL MACHINE TEST RESULTS CORRECTED FOR MACHINE STIFFNESS USING TBE PROPOSED MODEL

SEA ICE

For t h i s t y p e o f i c e , t h e r e s u l t s o f c o m p r e s s i o n t e s t s p e r - formed by t h e a u t h o r s i n t h e f i e l d on g r a n u l a r s e a i c e u s i n g two d i f f e r - e n t t e s t machines ( S o i l t e s t CT-405; T r i - T e s t 50) w i t h b o t h c o m p l i a n t and

s t e e l

p l a t e n s ( F r e d e r k i n g a n d Timco, 1 9 8 3 ; 1 9 8 4 ) viere c o m p a r e d to t h e r e s u l t s o f tests made by Wang ( 1 9 7 9 ) o n t h e same t y p e o f s e a ' i c e u n d e r l a b o r a t o r y c o n d i t i o n s u s i n g a c l o s e d - l o o p

t e s t

m a c h i n e . I n a l l cases, t h e test t e m p e r a t u r e was a p p r o x i m a t e l y -lOeC, a n d t h e ice was o f com- p a r a t i v e s a l i n i t y . T h e r e s u l t s f o r t h e s e tests a r e p r e s e n t e d i n F i g u r e 4 a . S i m i l a r t o t h e r e s u l t s f o r t h e f r e s h w a t e r ice t e s t s , t h e a s m e a s u r - e d s t r e n g t h o f t h e ice is less t h a n t h o s e f o r c o m p a r a b l e s t r a i n r a t e s o b t a i n e d w i t h t h e c l o s e d - l o o p m a c h i n e . S i n c e t h e elastic m o d u l u s o f t h e ice was n o t m e a s u r e d i n t h e s e tests, a n e s t i m a t e o f it was made by u s i n g t h e r e l a t i o n s h i p b e t w e e n t h e e l a s t i c m o d u l u s (E) a n d t h e b r i n e w l u m e G R A N U L A R S E A I C E T = - 1 0 ' C 0 F R E D E R K I N G A N D T l M C O ( I 9 8 3 a ) - C O M P L I A N T P L A T E N S - S O I L T E S T P R E S S - -0 F R E D E R K I N G A N D T l M C O ( 1 9 8 3 a ) - S T E E L P L A T E N S - S O I L T E S T P R E S S -

-

- - - W A N G ( 1 9 7 9 ) I-C L O S E D - L O O P C O N V E N T I O N A L ( U N C O R R E C T E D ) [ a ] I I I I

l 1 1

1 1

_{I 1 1 1 1 1 1}

-

- W A N G ( 1 9 7 9 ) ' C L O S E D - L O O P 0 C O N V E N T I O N A L - (CORRECTED)

~ r u

I

,

,

1 1 1 1 1

I

I

1 1 1 1 1 1 1

I

I

I 1 1

1 1 1

S T R A I N R A T E ( s - ' 1

FIGURE 4 STRENGTH-STRAIN RATE RELATIONSHIP FOR GEfANULAR SEA ICE

SHOWING WANG'S LABORATORY RESULTS OBTAINED USING CLOSED

LOOP MACHINE AND FREDERKING AND TIMCO'S FIELD RESULTS

OBTAINED USING CONVENTIONAL MACHINES ( a ) UNCORRECTED, ( b )

( u b ) determined f o r s e a i c e by Mudrey (1977)

,

E = 5.32

-

13% m a . Using t h e s e v a l u e s and e q u a t i o n ( 4 ) , t h e r e s u l t s of t h e t e s t s k r Frederking and Timco were re-analysed and a r e p r e s e n t e d i n F i g u r e 4 The c o r r e c t e d v a l u e s compare w e l l with t h o s e of Wang.

The method o u t l i n e d i n t h i s n o t e , based on a knowledge o f t h e t e s t system s t i f f n e s s and specimen modulus, a p p e a r s t o p r o v i d e a r e a s o n a b l e f i r s t approximation for c o r r e c t i n g s t r a i n r a t e s i n s t r e n g t h t e s t s . The t e c h n i q u e can be a p p l i e d t o i n t e r p r e t i n g d a t a a l r e a d y i n t h e l i t e r a t u r e i f t h e t e s t machine s t i f f n e s s is known. I t a l s o p r o v i d e s a r a t i o n a l e f o r using c o n v e n t i o n a l t e s t machines i n f i e l d t e s t i n g .

REFERENCES

F r e d e r k i n g , R.M.W. and Timco, G.W., 1983. u n i - a x i a l Compressive S t r e n g t h and Deformation of B e a u f o r t Sea Ice. Proc. POAC 83, M1. I, p. 89-98, H e l s i n k i , Finland.

F r e d e r k i n g , R.M.W. and Timco, G.W., 1984. Compressive Behaviour o f Beaufort Sea I c e Under k r t i c a l and H o r i z o n t a l Loading. Proc. 3rd I n t . Symp. on Offshore Mech. and A r c t i c Technology, M1. 111, p. 145-149, New O r l e a n s , U.S.A.

Haynes, F.D:, 1979. Temperature E f f e c t on t h e ~ n i - a x i a l S t r e n g t h of I c e . Proc. POAC 79, M1. I, p. 667-681, ~ r o n d h e i m , Norway.

S i n h a , N.K., 1981a. Comparative Study of I c e S t r e n g t h Data. Proc. IABR Symp. on I c e , M1. 11, p. 581-595, Quebec C i t y , Canada.

S i n h a , N.K., 1981b. Rate S e n s i t i v i t y of Compressive S t r e n g t h of' Columnar-Grained I c e . Exp. Mech. 21, No. 6, p. 209-218.

S i n h a , N.K., 1982. Constant S t r a i n - a n d S t r e s s - R a t e Compressive S t r e n g t h o f Columnar-Grained Ice. J. Mat. S c i . 17, p. 785-802.

S i n h a , N.K. and F r e d e r k i n g , R.M.W., 1979. E f f e c t o f Test System S t i f f - n e s s on S t r e n g t h of I c e . Proc. POX 79, M1. I, p. 708-717; Trondheim, Norway:

T r a e t t e b e r g , A., Gold, L.W. and F r e d e r k i n g , R.M.W., 1975. The S t r a i n Rate and Temperature Dependence o f Young's Modulus o f I c e . Proc. 3rd IAHR Symp. on I c e , p. 479-486, Hanover, N.H., U.S.A.

M u d r e y , K.D., 1977. Determination o f EYrchanical Sea I c e P r o p e r t i e s by

Large-Scale F i e l d Beam Experiments. Proc. POX 77, M1. I, p. 529-543, S t . John's, Canada.

Wang, Y.S., 1979. C r y s t a l l o g r a p h i c S t u d i e s and S t r e n g t h Tests o f F i e l d I c e i n t h e Alaskan Beaufort Sea. Proc. POX 79, M1. I, p. 651-665, Trondheim, Norway.

T h i s p a p e r , w h i l e being d i s t r i b u t e d i n r e p r i n t form by t h e D i v i s i o n of B u i l d i n g R e s e a r c h , remains t h e c o p y r i g h t of t h e o r i g i n a l p u b l i s h e r . It s h o u l d n o t be r e p r o d u c e d i n whole o r i n p a r t w i t h o u t t h e p e r m i s s i o n of t h e p u b l i s h e r . A l i s t of a l l p u b l i c a t i o n s a v a i l a b l e from t h e D i v i s i o n may be o b t a i n e d by w r i t i n g t o t h e P u b l i c a t i o n s S e c t i o n , D i v i s i o n of B u i l d i n g R e s e a r c h , N a t i o n a l R e s e a r c h C o u n c i l of C a n a d a , O t t a v a , O n t a r i o ,

K I A OR6.

Ce document e s t d i s t r i b u 6 sou8 forme d e t i r e - i l - p a r t par l a D i v i s i o n d e s r e c h e r c h e 8 e n b l t i m e n t . Les d r o i t s d e r e p r o d u c t i o n s o n t t o u t e f o i s l a p r o p r i € t € d e 1 1 6 d i t e u r o r i g i n a l . Ce d o c u m e n t n e p e u t 8 t r e r e p r o d u i t en t o t a l i t 6 ou en p a r t i e s a n s l e consentement d e l ' i d i t e u r . Une l i s t e d e s p u b l i c a t i o n s d e l a D i v i s i o n p e u t 8 t r e obtenue en Q c r i v a n t a l a S e c t i o n d e s p u b l i c a t i o n s . D i v i s i o n d e s r e c h e r c h e s e n b l t i m e n t , C o n s e i l n a t i o n a l d e r e c h e r c h e s Canada, O t t a v a , h t a r i o . K1A

OR6.