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Static and dynamic ice loads on the Yamachiche Bend lightpier,
1984-86
Frederking, R. M. W.; Haynes, F. D.; Hodgson, T. P.; Sayed, M.
https://publications-cnrc.canada.ca/fra/droits
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S e r I
TH1
- -no.
1503
National Research
Conseil national
1
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Council Canada
BLDG
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recherche8 Canada
Institute for
lnstitut de
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recherche en
Construction
construction
Static and Dynamic Ice Loads on the
Yamachiche Bend Lightpier, 1984
-
86
by R. Frederking,
F.D.Haynes et al
Appeared in
Proceedings 8th International IAHR
Symposium on Ice
lowa City, lowa, August 18- 22, 1986
Vol. Ill, p. 115-126
(IRC Paper No. 1503)
Reprinted with permission
Price $3.00
NRCC 28606
Des capteurs de mesure des charges de glace ont kt& instailis sur le pilier d t la courbe Yarnachiche, sur le Saint-Laurent, en avai de MontrCal.
Des
panneaux constitues de plaques d'acier appuyies s w des celIules extensomEtriques sant utilisB pour mesurer les charges statiques, et des acctSltrom&aes servent B mesurer Its charges dynarniques. Onmonue i c i comment ce s y s t h a fonctionnk au c o r n des annees 1983-19R4 A 1985-1986 et on fournit quelques estimations pdliminaires concernant les forces globales que la glace cxerce silr le pilier.
Iowa
City,
Iowa
I
STATIC AND DYNAMIC ICE U A D S ON THE YAMACHICHE BEND LIGHTPIER, 1984-86
R.
Frederking N a t i o n a l Research C o u n c i l Ottawa,of
Canada
CanadaCold Regions R e s e a r c h Hanover
,
and E n g i n e e r i n g L a b o r a t o r y NH,
U.S.A.
I T r a n s p o r t Canada CanadaM.
Sayed N a t i o n a l R e s e a r c h C o u n c i l of Canada O t t a w a , Canada ABSTRACTI c e l o a d m e a s u r i n g s e n s o r s were i n s t a l l e d on t h e Yamachiche Bend
I
l i g h t p i e r i n t h e S t . Lawrence R i v e r downstream f r o m M o n t r e a l . P a n e l s l c o n s i s t i n g of s t e e l p l a t e s s u p p o r t e d on l o a d c e l l s are u s e d t o measures t a t i c l o a d s w h i l e a c c e l e r o m e t e r s are u s e d t o m o n i t o r dynamic l o a d s . O p e r a t i o n of t h e s y s t e m o v e r t h e w i n t e r s of 1983-84 t o 1985-86 i s
l d e s e r i b e d and some p r e l i m i n a r y estimates o f t h e t o t a l i c e f o r c e s on t h e
INTRODUCTION
P r e d i c t i o n s of i c e l o a d s on s t r u c t u r e s c a n be made from a n a l y t i c a l and p h y s i c a l models, b u t t h e models n u s t be based on f u l l - s c a l e o b s e r v a t i o n s f o r c a l i b r a t i o n and v e r i f i c a t i o n . Owing t o t h e d i f f i c u l t i e s of c a r r y i n g , o u t such measurements s u c c e s s f u l l y , r e l a t i v e l y few p r o j e c t s have a s y e t been c a r r i e d o u t a t f u l l - s c a l e .
T r a d i t i o n a l l y , a p r e s s u r e of 2.8 MPa (400 p s i ) h a s been adopted i n c a l c u l a t i n g i c e l o a d s on b r i d g e p i e r s . The Canadian S t a n d a r d s
A s s o c i a t i o n (1978) and t h e M i n i s t r y of T r a n s p o r t a t i o n and Communications (1983), h t a ~ i 0 , have proposed t h a t under c e r t a i n c i r c u m s t a n c e s lower d e s i g n i c e p r e s s u r e s c o u l d be used. C o n s i d e r a b l e judgement i s r e q u i r e d , however, i n s e l e c t i n g t h e a p p r o p r i a t e l e v e l f o r d e s i g n purposes. Such d e c i s i o n s a r e u s u a l l y based on q u a l i t a t i v e i n f o r m a t i o n and argument. F i e l d measurements of a c t u a l ice l o a d s are needed t o e s t a b l i s h maximum l o a d s and t h e p r o b a b i l i t y of e x c e e d i n g g i v e n l o a d l e v e l s .
F i e l d measurements of r i v e r and l a k e i c e on s t r u c t u r e s i n c l u d e t h o s e r e p o r t e d by Neill (1976), L i p s e t t and Gerard (1980), Huiskamp (1983), Danys (19811, and Haynes and Sodhi (1983), who a l s o gave a comprehensive review of a v a i l a b l e l i t e r a t u r e . E m p i r i c a l f o r m u l a s f o r i c e l o a d s were a l s o g i v e n by Korzhavin (1971), Afanas'yev e t a l . (1979) and N e i l l
(1981).
A program of i c e f o r c e measurements i s b e i n g c a r r i e d o u t a t t h e Yamachiche Bend l i g h t p i e r i n t h e S t . Lawrence R i v e r downstream from Montreal. Each i c e l o a d measuring p a n e l comprises a s t e e l p l a t e s u p p o r t e d on t h r e e load c e l l s . T h i s h a s been supplemented w i t h
a c c e l e r o m e t e r s i n o r d e r t o p r o v i d e a b e t t e r i n d i c a t i o n of dynamic i c e loads.
Over t h e p e r i o d 1983-1986 measurements were made w i t h b o t h l o a d p a n e l s f o r s t a t i c l o a d s and a c c e l e r o m e t e r s f o r dynamic l o a d s . A t t h e same time g e n e r a l i c e c o n d i t i o n s were c a t a l o g u e d . T h i s p a p e r w i l l b r i e f l y d e s c r i b e t h e measuring systems used, p r e s e n t t h e r e s u l t s , d e s c r i b e t h e a n a l y s i s t e c h n i q u e , and compare t h e i c e l o a d s p r e d i c t e d from d i r e c t s t a t i c and a c c e l e r o m e t e r measurements.
STATIC ICE FORCE MEASUREMENTS
The p i e r a t Yamachiche Bend is c o n i c a l a t w a t e r l e v e l , w i t h a s l o p e of 4 v e r t i c a l t o 1 h o r i z o n t a l . The d i a m e t e r a t i c e l e v e l i s a p p r o x i m a t e l y 4 m. D e t a i l e d drawings of t h e p i e r a r e a v a i l a b l e (Danys, 1975). F i v e p a n e l s a r e i n s t a l l e d on t h e west ( u p s t r e a m ) s i d e of t h e p i e r . It and i c e c o n d i t i o n s around i t a r e shown i n Fig. 1. The o r i g i n a l l o a d p a n e l s and e l e c t r o n i c s were r e c o n d i t i o n e d and upgraded i n 1983 ( F r e d e r k i n g e t a l . ,
1985). E x t e n s i v e f i e l d c a l i b r a t i o n t e s t s were c a r r i e d o u t when t h e p a n e l s were r e - i n s t a l l e d and a g a i n i n t h e summers of 1984 and 1985 t o v e r i f y t h e o p e r a t i o n of t h e system. These r e p e a t e d c a l i b r a t i o n tests i n d i c a t e d t h a t t h e c a l i b r a t i o n f a c t o r s ( r a t i o of l o a d t o s i g n a l v o l t a g e ) v a r i e d on a v e r a g e + l o % , and +25% i n a n extreme i n s t a n c e . One of t h e main problems i n c o n v e r t i n g t h e v o l t a g e s i g n a l t o l o a d was t h a t of s e l e c t i n g t h e a p p r o p r i a t e " z e r o l o a d " s i g n a l . The method v a r i e d from s e a s o n t o s e a s o n and w i l l be d i s c u s s e d l a t e r . S i n c e a c c e s s t o t h e p i e r i s v e r y r e s t r i c t e d i n t h e w i n t e r , a t e l e m e t r y s y s t e m i s used t o t r a n s f e r d a t a t o a s h o r e s t a t i o n where i t i s recorded. Because t h e d a t a a r e p o t e n t i a l l y overwhelming, a s t r a t e g y f o r sampling and condensing had t o be adopted. Again d e t a i l s w i l l be d i s c u s s e d on a s e a s o n by s e a s o n b a s i s .
F i g u r e 1. Yamachiche p i e r , 19 January 1984
DYNAMIC ICE FORCE MEASUREMENTS
The Yamachiche l i g h t p i e r i s s u b j e c t e d t o dynamic a s w e l l a s s t a t i c i c e f o r c e s . The dynamic i c e f o r c e s o c c u r as a r e s u l t of i c e f a i l u r e i n c r u s h i n g and bending, and a s a r e s u l t a l s o of i c e impact and r o t a t i o n round t h e p i e r . Dynamic f o r c e s a r e of s h o r t d u r a t i o n , e.g., 0.01 t o 2 s , b u t can be of h i g h magnitude; i n f a c t , t h e y can be s e v e r a l t i m e s h i g h e r t h a n t h e s t a t i c l o a d s . High l o c a l p r e s s u r e s c a n be caused by dynamic
l o a d s . Such l o c a l p r e s s u r e s can c a u s e damage t o s t r u c t u r e s , as h a s been
o b s e r v e d a t t h e Yukon R i v e r b r i d g e (Buska, 1986) where t h e s t e e l n o s e
armour was t o r n from one of t h e c o n c r e t e b r i d g e p i e r s and s p a l l i n g of t h e
c o n c r e t e was caused d u r i n g t h e ice r u n of 1985.
The p r e s e n t a p p r o a c h f o r measuring dynamic i c e f o r c e s u s e s a t r a n s f e r f u n c t i o n d e r i v e d from r e s u l t s of "plucking" t e s t s on t h e l i g h t p i e r . ("Plucking" was done by s t e p u n l o a d i n g , i.e. by a p p l y i n g a l o a d t o t h e p i e r t h e n a b r u p t l y removing i t by r u p t u r e of a notched t e n s i o n member.)
The t e s t s were c a r r i e d o u t i n September 1984 (Haynes, 1986) and y i e l d e d a
t r a n s f e r f u n c t i o n m a t r i x , v i z . ,
..
where {x(w)} i s t h e measured a c c e l e r o m e t e r r e s p o n s e s i g n a l and { f (w)} i s t h e a p p l i e d f o r c e v e c t o r , both of which a r e i n t h e frequency domain v i a a
F o u r i e r transform. The unknown f o r c e v e c t o r due t o a n i c e l o a d i n g e v e n t
call be Found from
..
where {x(w)} i s now t h e measured r e s p o n s e v e c t o r d u r i n g i c e l o a d i n g .
T h i s f o r c e can be found i n t h e t i m e domain by t h e i n v e r s e F o u r i e r
t r a n s f o r m m { ~ ( t ) } =
.f
[ H ( u ) ] - ~ {x(w)}e i w t dw -aD where t h e d e s i r e d i c e f o r c e i s { ~ ( t ) } . S i x a c c e l e r o m e t e r s a t t h r e e d i f f e r e n t l e v e l s (same l o c a t i o n s as f o r t h e p l u c k i n g t e s t s ) were mounted on t h e p i e r . A t r i g g e r i n g s y s t e m a c t i v a t e da magnetic t a p e r e c o r d e r whenever a t h r e s h o l d a c c e l e r a t i o n was exceeded.
A time s i g n a l was a l s o p u t on t h e r e c o r d s o t h a t l o a d s measured by
RESULTS
1983-84 Season
O p e r a t i o n of t h e system s t a r t e d i n mid-November 1983. The equipment and r e c o r d i n g p r o c e d u r e s
were
t e s t e d and open w a t e r s i g n a l swere
determined f o r a n i n i t i a l p e r i o d of f i v e weeks when t h e r e w a s noice
around t h e p i e r . During a v i s i t t o t h e s i t e on 19 December 1983 t h e w a t e r w a s s t i l l open, w i t h o n l y s c a t t e r e d s l u s h . Measurements c o n t i n u e d u n t i l 18 A p r i l1984, a l t h o u g h i c e d i s a p p e a r e d s e v e r a l weeks e a r l i e r . There were some shut-downs between 19 December and 1 8 A p r i l owing t o power f a i l u r e s a t t h e p i e r .
Three v i s i t s were made d u r i n g measurement p e r i o d t o o b s e r v e
i c e
c o n d i t i o n s and t o check t h e o p e r a t i o n of t h e equi,pment. By 19 January a s o l i d
ice
c o v e r had formed and a r u b b l e a c c u n u l a t i o n s u r r o u n d e d t h e p i e r . The r u b b l e had a n o v a l shape, e x t e n d i n g from4
t o 5 m i n f r o n t of most p a n e l s . I c e b l o c k s c o n s t i t u t i n g t h e r u b b l e v a r i e d i n t h i c k n e s s from 0.2 t o a p p r o x i m a t e l y 0.6 m. Holes d r i l l e d i n t h e r u b b l e showed t h a t t h e r u b b l e k e e l was grounded a t a d e p t h of 2.5 m, i.e., i t reached t h e f o u n d a t i o n of t h e p i e r . I c e t h i c k n e s s o u t s i d e t h e r u b b l e wasa p p r o x i m a t e l y 0.6 m. Another v i s i t was made on 1 February when i c e c o n d i t i o n s were v e r y similar t o t h o s e of 19 January. By t h e n e x t v i s i t on 30 March, open w a t e r s u r r o u n d e d t h e p i e r , w i t h o n l y a few i s o l a t e d i c e b l o c k s d r i f t i n g about.
The f o l l o w i n g s t r a t e g y was adopted t o p r o v i d e a r e a s o n a b l y a c c u r a t e d e s c r i p t i o n of t h e l o a d h i s t o r y and d e t a i l s of any s i g n i f i c a n t e v e n t s . Outputs were r e c o r d e d f o r 1 min a t lO-min i n t e r v a l s . During e a c h of t h e s e sampling p e r i o d s t h e s i g n a l s were r e c o r d e d once e v e r y 2 s. I n a d d i t i o n , r e c o r d i n g of a l l s i g n a l s w a s t r i g g e r e d i f any one s i g n a l exceeded a c r i t i c a l v a l u e , t a k e n a s 0.1 V , which c o r r e s p o n d s t o a p p r o x i m a t e l y 13.4
kN
o n a n i n d i v i d u a l l o a d c e l l . For c a l c u l a t i o n of l o a d s t h e minimum " z e r o l o a d " v o l t a g e o v e r t h e s e a s o n was s e l e c t e d s i n c e i t would produce c o n s e r v a t i v e ( h i g h ) l o a d v a l u e s . A t y p i c a l r e c o r d of f o r c e v e r s u s t i m e f o r e a c h p a n e l i s p r e s e n t e d i n Fig. 2. These a r e h o u r l y mean f o r c e v a l u e s , b u t maximum v a l u e s of f o r c e s were n o t s i g n i f i c a n t l y h i g h e r .I NORTH 1
70
PRNELnl (SOUTH
D E C E M B E R 1983
Figure 2. Hourly mean i c e force vs time, 19-29 December 1983
NORMAL STRESS L 100 kNlm SHEAR NORMAL d RESULTANT ICE FORCE DIRECTION
The f i v e l o a d p a n e l s c o v e r t h e w e s t s i d e of t h e p i e r , f a c i n g upstream, t h e d i r e c t i o n of predominant
ice
movement ( F i g .3).
A t t h e o b s e r v e d e l e v a t i o n of i c e c o n t a c t w i t h t h e p a n e l s t h e f o r c e s would be a c t i n g on a h o r i z o n t a l l e n g t h of a p p r o x i m a t e l y0.27 m
of e a c h p a n e l . Measured l o a d s were c o n v e r t e d t o l o a d p e r u n i t l e n g t h by d i v i d i n g t h e g i v e n v a l u e s by 0.27 m. The a v e r a g e i c e t h i c k n e s s was a p p r o x i m a t e l y 0.6 m f o r most of t h e season. Thus, nominalstresses
were c a l c u l a t e d by d i v i d i n g t h e l o a d s by t h e a r e a (0.162 rn2).E s t i m a t i n g t h e t o t a l i c e f o r c e on t h e p i e r would r e q u i r e knowledge of t h e normal and s h e a r stresses a l o n g i t s p e r i m e t e r . The p r e s e n t arrangement g i v e s o n l y normal stresses on p a r t of t h e p e r i m e t e r . Measurements were
e x t r a p o l a t e d t o c a l c u l a t e t h e t o t a l ice f o r c e u s i n g f o u r methods. The f i r s t assumes t h a t stresses a c t on t h e w e s t h a l f of t h e p i e r p e r i m e t e r . Normal s t r e s s e s a r e e x t r a p o l a t e d o v e r s e c t o r s a s s i g n e d t o t h e p a n e l s . T a n g e n t i a l s t r e s s e q u a l t o 0.2 of t h e normal stress is added on e a c h s e c t o r . The r e s u l t a n t f o r c e component i n t h e e a s t e r l y d i r e c t i o n was c o n s i d e r e d t o be t h e t o t a l load. A t y p i c a l stress d i s t r i b u t i o n a t one i n s t a n t i s shown i n Fig. 3. The second method c o n s i d e r s a s i m i l a r , normal stress d i s t r i b u t i o n , b u t n o t a n g e n t i a l stresses a r e added. The southernmost p a n e l , however, o f t e n measured t h e h i g h e s t stresses.
Consequently, a t h i r d method was a d o p t e d where stresses a r e assumed t o a c t on t h e h a l f of t h e p e r i m e t e r c e n t r e d around t h i s panel. Normal and t a n g e n t i a l stresses a r e assumed t o be s y m m e t r i c a l a b o u t i t . The f o u r t h method i s s i m i l a r t o t h e t h i r d , b u t e x c l u d e s t a n g e n t i a l stresses.
Examples of t h e t o t a l l o a d c a l c u l a t e d a r e shown i n Fig. 4. It may be s e e n t h a t methods one and t h r e e produce l a r g e r t o t a l l o a d v a l u e s t h a n methods two and f o u r .
1984-85 Season
For t h i s s e a s o n a d i f f e r e n t r e c o r d i n g s t r a t e g y was u s e d , i n t h i s c a s e r e c o r d i n g c o n t i n u o u s l y w i t h a 2 0 s s c a n i n t e r v a l . A t i m e l a p s e f i l m was a l s o made u s i n g a Super 8 movie camera t a k i n g one frame e v e r y h a l f hour. The f i l m was used t o c h a r a c t e r i z e ice c o n d i t i o n s a t t h e p i e r and t o e s t a b l i s h zero-load v o l t a g e s . T h i s allowed t h e zero-load v o l t a g e t o be r e - s e t s e v e r a l times d u r i n g t h e s e a s o n , based on observed open w a t e r p e r i o d s . There were a g a i n problems w i t h t h e power s u p p l y t o t h e p i e r , s o t h a t a r e c o r d was o b t a i n e d f o r o n l y p a r t s of February and March 1985.
LEGEND
0
l
II
18 Za ma W )I m SO
DECEMBER JANUARY
1083 lQ84
Figure
4.
Hourly mean of t o t a l ice f o r c e a c t i n g on p i e r , four methods ofcalculation, December
1983
0 100 200 300 400 600 600
TOTAL FORCE ,KN
Figure
5.
Comparison of cumulative d i s t r i b u t i o n of t o t a l force, calculated by method 1 , 1983/84 and February 1985I c e c o n d i t i o n s were s i m i l a r t o t h o s e of t h e 1983-84 s e a s o n . I n g e n e r a l , t h e n a t u r e of t h e r e c o r d s w a s s i m i l a r t o t h a t of t h e p r e v i o u s s e a s o n , b u t o n a v e r a g e t h e t o t a l f o r c e on t h e p i e r was less ( F i g - 5 ) . 1985-86 Season During t h e 1984-85 s e a s o n s e v e r a l l o a d c e l l s had f a i l e d , w i t h t h e consequence t h a t no r e s u l t s c o u l d be o b t a i n e d f r o m t h e w e s t e r n m o s t p a n e l . Tlris was u n f o r t u n a t e , b u t i t d i d p r o v i d e a n o p p o r t u n i t y t o i n s t a l l f o r t h e 1985-86 s e a s o n a n add-on p a n e l t y p e of t r a n s d u c e r n o r m a l l y u s e d f o r making i n s i t u p r e s s u r e measurements i n i c e c o v e r s . It w a s a n "IDEAL" p a n e l t r a n s d u c e r s u p p l i e d by T e r r a s c i e n c e a n d c o n f i g u r e d t o f i t d i r e c t l y o v e r t h e o l d i l n s e r v i c e a b l e p a n e l . Rated c a p a c i t y was 3 MPa. The p a n e l t r a n s d u c e r w a s 2.5 m h i g h by a p p r o x i m a t e l y 0.5 m wide a n d w a s d i v i d e d i n t o f i v e h o r i z o n t a l s e c t o r s s o t h a t a v e r t i c a l d i s t r i b u t i o n of ice l o a d c o u l d be o b t a i n e d . A small m e t e o r o l o g i c a l s t a t i o n w i t h d a t a l o g g e r was p l a c e d on t h e p i e r and t h e t i m e - l a p s e movie camera was a g a i n used.
The s a m p l i n g s t r a t e g y f o r t h e t e l e m e t r y s y s t e m was t h e same a s t h a t f o r t h e 1984-85 s e a s o n . The d a t a l o g g e r a t t h e m e t e o r o l o g i c a l s t a t i o n had
e x t r a c h a n n e l s a v a i l a b l e and t h e
IDEAL
p a n e l s i g n a l s were r e c o r d e d on i t a s w e l l . The l o g g e r was programmed t o r e c o r d t h e mean and maximum v a l u e s o v e r e a c h h a l f - h o u r i n t e r v a l . The a n a l o g u e t a p e r e c o r d e r on which t h e a c c e l e r a t i o n s were r e c o r d e d had o n e f r e e c h a n n e l and t h e m i d d l e s e c t i o n o f t h e IDEAL p a n e l w a s a l s o f e d i n t o i t . With t h i s o v e r l a p p i n g o f r e c o r d s i t was p o s s i b l e t o compare r e s u l t s o b t a i n e d by d i f f e r e n t r e c o r d i n g s t r a t e g i e s a n d d i f f e r e n t measurement a p p r o a c h e s .The r e s u l t s of t h e 1985-86 s e a s o n a r e s t i l l b e i n g a n a l y s e d , b u t a s a m p l e r e c o r d w i l l he p r e s e n t e d . A dynamic i c e l o a d i n g e v e n t Erom t h e middle s e c t o r of t h e IDEAL p a n e l i s shown i n Fig. 6a; t h e c o n c u r r e n t
a c c e l e r o m e t e r v e r s u s t i m e s i g n a l i s shown i n F i g . 6b. The a c c e l e r o m e t e r s i g n a l t r a n s f o r m e d t o t h e f r e q u e n c y domain was u s e d i n E q u a t i o n ( 3 ) t o o b t a i n t h e dynamic i c e f o r c e . A maximum dynamic f o r c e of 37
kN
on t h e p i e r was found f o r t h i s e v e n t . T h i s i s l o w e r t h a n t h e t o t a l i c e f o r c e o f 200 kN on t h e middle s e c t i o n of t h e IDEAL p a n e l d e t e r m i n e d from t h es t a t i c f o r c e measurements. The dynamic l o a d i s b a s e d o n a c c e l e r a t i o n s of t h e l i g h t p i e r and t h e r e f o r e d o e s n o t i n c l u d e s t a t i c l o a d s , which may a l s o be p r e s e n t . An i c e p i l e - u p a t t h e b a s e of t h e l i g h t p i e r would b e a n
added mass and a t t e n u a t e t h e a c c e l e r o m e t e r s i g n a l s . F i g u r e 6 i n d i c a t e s s i g n i f i c a n t peak l o a d s , however, and t h e dynamic i c e l o a d s c o r r e s p o n d t o t h e s e peaks. The a n a l o g u e t a p e r e c o r d e r , which c a n r e c o r d high-frequency s i g n a l s , showed t h a t p a n e l t r a n s d u c e r s c a n d e t e c t dynamic i c e l o a d s .
1
TIME, s
F i g u r e 6. Comparison of a c c e l e r o m e t e r r e c o r d and IDEAL p a n e l r e c o r d f o r a n i c e l o a d i n g e v e n t
SrnIMAKY
( 1 ) For t h e 1983-84 s e a s o n t h e maximum s t a t i c i c e f o r c e was 600 kN,
g e n e r a t e d by a 0.6-m t h i c k i c e c o v e r a c t i n g on a p i e r w i d t h of 4 m a t t h e w a t e r l i n e . Loading e v e n t s were s t a t i c , l a s t i n g s e v e r a l h o u r s t o a few days. A s t a t i c i c e c o v e r surrounded t h e p i e r f o r most of t h e i c e season.
( 2 ) For t h e 1984-85 s e a s o n t h e maximum s t a t i c i c e f o r c e was a b o u t 300 kN. I c e c o n d i t i o n s were g e n e r a l l y s i m i l a r t o t h o s e of t h e p r e v i o u s
season.
( 3 ) These i c e f o r c e s a r e s u b s t a n t i a l l y lower t h a n t h e v a l u e c a l c u l a t e d from CSA(1978): 2200
kN
f o r a n e f f e c t i v e c r u s h i n g p r e s s u r e of700 kPa,
ice
t h i c k n e s s 0.6m
and p i e r w i d t h of 4 m.( 4 ) For t h e 1985-86 s e a s o n a d i r e c t comparison of s t a t i c and dynamic i c e
f o r c e s was made. The measured dynamic f o r c e s were s u b s t a n t i a l l y less
t h a n t h e
s t a t i c
f o r c e s .(5)
F u r t h e r a n a l y s i s i s r e q u i r e d t o r e l a t eice
f o r c e s on t h e p i e r t o t h eice c o n d i t i o n s .
ACKNOWLEDGEMENTS
The a u t h o r s wishes t o acknowledge t h e t e c h n i c a l a s s i s t a n c e of J * N e i l ,
IRCINRCC, and W. B e r t h e l e t , A. Godin and R. S i l b e r h o r n , MOT, i n c a r r y i n g o u t t h i s work. T h i s p a p e r i s a c o n t r i b u t i o n from t h e I n s t i t u t e f o r Research i n C o n s t r u c t i o n , N a t i o n a l Research Council of Canada.
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