Report on tests of paper snow fence

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Report on tests of paper snow fence

Pearce, D. C.

NATIONAL RESEARCH COUNCIL OF CANADA

DIVISION OF BUILDING HESEAHCH

REPORT ON TESTS OF PAPER SNOW FENCE

by D . C . P e a r c e A N A L Y Z E D T h i s R e p o r t must 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 w r i t t e n p e r m i s s i o n f r o m t h e N a t i o n a l R e s e a r c h C o u n c i l Ottawa 2 8 J u n e , 1 9 5 0 . DRR R e p o r t

T

4

REP3RT

ON

TESTS OF PAP-3R SNO!;i FENCE

--.---

-D.

S . P e a r c e

E a r l y i n O c t o b e r

1 9 4 9 ~

t h e D i v i s i o n o f E u i l d i n g R e s e a r c h was a p p r o a c h e d t,y t h e D i r e c t o r . ~ f V;oodlands R e s e a r c h o f t h e P u l p and P a p e r R e s e a r c h I n s t i t u t e o f Canada and a s k e d t o t e s t a r e c e n t l y - d e v e l o p e d p a p e r mesh snow.-fence. The c h i e f a d v a n t a g e o f t h i s f e n c e i s t h a t i t i s c o n s i d e r a b l y c h e a p e r t h a n t h e w o o d - s l a t t y p e . A s t h e member companies o f t h e P u l ? and P a p e r 2 e s e a r c h I n s t i t u t e make e x -

t e n s i v e u s e o f snow f e n c i n ~ e v e r y w i n t e r , t h e y were a n x i o u s t o o i t a i n a r e p o r t o f t h e p e r f o r ~ a n c e o f t h e p a 7 e r mesh f e n c e . 4 c - c o r d i n g l y , a r r a n ~ e r n e n t s wers completed w i t h b r . J .

H.

P a r k i n o f t h e D i v i s i o n o f h ' e c h a n i c a l S n ~ i n e e y i n g f o r t h e u s e o f t h e c o l d c h a m t e r s o f t h a t g i v i s i o n , and w i t h t h e F e d e r a l D i s t r i c t Commission (who m a i n t a i n t h e g r o u n d s o f t h e l,!ontreal Road L a b o r a t o r i e s ) t o a l l o w s a m p l e s t o b e t e s t e d b o t h i n t h e f i e l d and i n t h e low t e m p e r a t u r e l a b o r a t o r i e s . "is i s a r e p o r t on t h e p e r f o r m a n c e of t h e p a p e r z e sh f e n c e u n d e r t e s t

.

TZ?T FHOCE3TYRZS _-- ( 1 ) F i e l d l e s t ~ The f i r s t s a m p l e q o f p a ? e r n e s h f e n c e were e r e c t e d o n t h e I " , , o n t r e a l Road s i t e gf t h e : l a t i o n 3 1 R e s e a r c h C o u n c i l o n N9vember

19,

1149.

The f e n c e w a s l o c a t e d on t h e w e ~ t s i d e o f t h e r o a d o p p o s i t e b u i l d i n g s K-2 and A

- 3 .

T h i s s i t e was c h o s e n a s o f f e r i n g t h e

s e v e r e s t wind c o n d i t i o n s on t h e p r o p e r t y . The p a p e r mesh was

a n c h o r e d by w i r e d i r e c t l y t o t h e o n e - i n c h d i a m e t e r i r o n p i p e s s p a c e d a p ? r o x i m a t e l y

15

f e e t on c e n t r e s , f o r m e r l y u s e d f o r m o u n t i n g a s t a n - d a r d v e r t i c a l s l a t - t y p e f e n c e . The p a p e r mesh was t h u s ? a r t o f a c o n t i n u o u s f e n c e 4 u n i t

reach in^

f r o m b u i l d i n ~ s PI:-1 t o &I-21. F i g u r e 1

i s a rlaD o f t n e f i e l d i n s t a l l a t i o ? ~ .

O r i g i n a l l y , t h e p a p e r .l!esh was a n c h o r e d by b i n d i n g t h e

m a r g i n w i r e s d i r e c t l y t o t h e s u ? p o r t s w i t h i r o n w i r e . Iiowever, t h r e e d a y s a f t e r p l a c e m e n t t h e p a p e r mesh began t o f a i l a t t h e s u p g o r t s . T h i s was a t t r i b u t e d t o wind a c t i o n o c c u r r i n g a t v e l o c i t i e s o f 2 5 mph. The m o u n t i n g method was t h e n c h a n g e d . The p a p e r mesh was s e c u r e l y bound b e t w e e n a s o f t w o o d b o a r d (1- Ly 2 - i n c h e s by 4 - f e e t l o n g ) a n d t h e i r o n u p r i g h t . T h i s p r e v e n t e d t h e a b r a s i o n c a u s e d by t h e f e n c e b l o w i n g a g a i n s t t h e s u ? p o r t s . T h i s method was employed t h r o u g h o u t t h e e n t i r e l e n g t h o f p a p e r mesh f e n c e . F i g u r e 2 i s a s k e t c h o f t h e two a n c h o r i n g m e t h o d s .

The h e a v y - g r a d e c r e o s o t e - i r r p r e g n a t e d mesh was r e c e i v e d and e r e c t e d on D e c e m t e r 2 1 ,

19/49.

I t was p l a c e d where s l a t - t y p e f e n c e h a d p r e v i o u s l y b e e n u s e d . Thus a c o n t i n u o u s p a p e r mesh f e n c e was i n c o r p o r a t e d i n t o t h e s l a t - t y p e f e n c e . 'This was deemed t h e

t e s t method f o r c o m p a r i s o n o f t h e two t y p e s o f f e n c e . P e r s o n a l i n s p e c t i o n s o f t h e f e n c e were c a r r i e d on t h r o u g h - o u t t h e w i n t e r . I n a d d f t i o n a p h o t o c r a p h i c r e c o r d o f t h e p e r f o r m a n c e was o b t a i n e d . L a b o r a t o r y T e s t s T h e r e were t h r e e p h a s e s o f l a t o r a t o r y t e s t i n g . The f i r s t method was t o e x p o s e t h e s a m p l e s t o a f r e e z e - t h a w t e m p e r a t u r e c y c l e l a s t i n g s e v e r a l d a y s . On c o n i p l e t i o n o f t h i s t e s t t h e p a p e r mesh was s u t j e c t e d t o a w a t e r s p r a y a t below f r e e z i n g t e m p e r a t u r e s , The r e s u l t was a v e r y s e v e r e i c i n g c o n d f t i o n . F i n a l l y t h e s a m p l e s were t e s t e d u n d e r combfned w i n d a n d p r e c f p f t a t i o n c o n d i t i o n s i n a n I c i n g wind t u n n e l . F o r t h e f r e e z e - t h a w t e s t , s a m p l e s

( 3 -

by 4 - f e e t ) were mounted on s u i t a b l e wooden f r a m e s

.

F i v e a u t o m a t i c a l l y r e c o r d i n g t h e r m o c o u p l e s w e r e a t t a c h e d t o e a c h . s a m p l e . The t e m p e r a t u r e c y c l i n g c o n t i n u e d throui;'n,out t??e ~ e r i o d f r o n !

9:OO

a . m o t o 4:00 pan!. e a c h d z y f o r s e v e n d a y s . ' I n a 2 d i t i o n , a r e c o r d o f t h e chamker a i r t e m p e r a - t u r e was o b t a i n e d . P r e l i m i n a r y o i ~ s e r v a t i o n s f n d i c 8 t e d n o t e r c p e r a t u r e g r a d i e n t s t o e x i s t n i t h 5 n t h e m e s h . ? u r t h e r m o r e , t h e t e m p e r a t u r e r e c o r d e d by t h e t h e r m o c o u p l e s was n o t a p p r e c i a k l y d i f f e r e n t f r o m t h e c h a m t e r a f r t e m p e r a t u - r e . C o n s e q u e n t l y o n l y t h e chanlker a i r t e m p e r a - t u r e r e c o r d s ( F i g u r e

3 )

a r e g i v e n i n t h i s r e p o r t .

The s a n e t e s t f r a ~ e was employed t o t e s t t h e p e r f o r m a n c e o f t h e p a p e r n e s h u n d e r i c i n g c o n d i t i o n s . F i g u r e

4

i s a p l o t o f t h e chamber a f r t e m p e r a t u r e d u r i n g t h i s t e s t . The s p r a y was o b t a i n e d f r o m f i v e p r e s s u r e n o z z l e s y i e l d i n g d r o p s o f a p p r o x i m a t e l y 1 0 0 m i c r o n s d f a m e t e r . S p r a y i n g was c o n t i n u e d f o r a p p r o x i m a t e l y t w e n t y m i n u t e s . F i g u r e s

5

and

6

i l l u s t r a t e t h e i c e d s a m p l e s o n c o m p l e t i o n o f s p r a y i n g . S m a l l e r s a m p l e s were employed f o r t h e i c i n g t u n n e l t e s t s . T h i s was n e c e s s a r y due t o t h e r e s t r i c . t e d t h r o a t ( 2 0 - t y 2 0 - i n c h e s ) of t h e t u n n e l . The s a n p l e , s e c u r e l y s t a p l e d t o a r i g i d wood f r a m e was mounted i n t h e t u n n e l a t a n a n ~ l e o f a p p r o x i m a t e l y

450

t o t h e a i r s t r e a ~ . T h i s a n g l e was n e c e s s a r y t o a l l o w a n a i r p a s s a g e a r o u n d t h e f r a ~ e i f t h e sample became c o m p l e t e l y c l o g g e d w i t h i c e . T e s t s were c a r r i e d o u t u n d e r s e v e r a l d i f f e r e n t c o n d i t f o n s

.

A l l r e l e v a n t d a t a were r e c o r d e d . F i g u r e

7

I l l u s t r a t e s t h e sample s e t u p i n t h e t u n n e l and F i g u r e

8

shows t h e i c e a c c u m u l a t i o n a f t e r s i ~ u l a t e d f r e e z i n g r a i n .

I n t h e ~ a j o r i t y o f t e s t s no damage c o u l d k,e v i s u a l l y ok- s e r v e d . T h e r e f o r e , some n e t h o d o f m e a s u r i n g d e t e r i o r a t i o n was n e c e s s a r y . The a v e r a g e f a i l i n g l o a d i n t e n s i o n of s e v e r a l f i b r e s from e a c h specimen was a d o p t e d a s a c r i t e r i o n of p e r f o r m a n c e . TEST

RESULTS

F i e l d T e s t s

The w i n t e r of 1949-50 was q u i t e u n u s u a l and n o t t o o w e l l s u i t e d f o r t h e s e t e s t s . The t o t a l s e a s o n a l s n o w f a l l of 8 5 i n c h e s was 2 i n c h e s below t h e 5 0 - y e a r n o r m a l . However, t h e numerous r a i n s and warm s p e l l s r e s u l t e d I n s h a l l o w snow d e p o s i t s o n t h e g r o u n d most o f t h e t i m e . Thus t h e f e n c e was e x p o s e d t o wind more t h a n would be e x p e c t e d u n d e r more n o r m a l c i r c u m s t a n c e s . F i & , u r e

9

i s a c h a r t o f t h e v a r i o u s m e t e o r o l o g i c a l e l e m e n t s a t Ottawa d u r i n g t h e w i n t e r 1949-50 *

The f i r s t f a i 1 u r . e ~ o c c u r r e d on November 2 5 , d u r i n g a s t o r m w i t h wind ~ p e e d s t o 25 mph. T h e r e was l i t t l e ?now o n t h e g r o u n d a t

t h i s t i m e . A s m e n t i o n e d p r e v i o u s l y , t h e s a n d w i c h - t y p e a n c h o r was t h e n i n s t a l l e d . T h i s m o d i f i c a t i o n gave s a t i s f a c t o r y s e r v i c e f o r some t i m e . F i g u r e 1 0 i s a p h o t o ~ r a n h of t h e f i e l d i n s t a l l a t i o n s on

Noven~ber 2 3 .

No f u r t h e r f a i l u r e s o c c u r r e d u n t i l J a n u a r y

14,

1 9 5 0 . L i t t l e snow was on t h e ground t h e n and g a l e - f o r c e winds were e x - p e r i e n c e d . 'rhree s e p a r a t i o n s o c c u r r e d i n t h e l i g h t - w e i g h t c r e o s o t e - i m p r e g n a t e J f e n c e . Two of t h e s e f a i l u r e s were a t a n c h o r 7 o i n t s w h i l e t h e t h i r d was l o c a t e d mid-way between two p o s t s . The f o r c e o f t h e wind had b e n t s e v e r a l o f t h e i r o n p o s t s s u p p o r t i n g b o t h p a p e r mesh and s l a t - t y p e f e n c e . F i g u r e s 11 and 1 2 a r e p h o t o g r a p h s o f two of t h e f a i l u r e s . The s e p a r a t i o n i l l u s t r a t e d i n Fi;ure 12 was p a t c h e d l y sewin& a n a d d i t i o n a l s e c t i o n of p a p e r mesh o v e r t h e t e a r .

F u r t h e r f a i l u r e s o c c u r r e d on J a n u a r y 1 8 t h d u r i n g a s t o r m accompanied t y wind g u s t s t o

45

mph. I n a l l , f i v e b r e a k s were o t - s e r v e d . One o f t h e s e o c c u r r e d a t an a n c h o r p o s t of t h e p a r r a f i n - i m p r e g n a t e d mesh. The r e m a i n d e r were i n t h e l i g h t - w e i g h t c r e o s o t e - i m p r e g n a t e d mesh. The h e a v y - w e i g h t c r e o s o t e - i m p r e g n a t e d mesh was n o t damaged. F u r t h e r m o r e , t h e f e n c e was s a g g i n g c o n s i d e r a t l y between t h e s u p p o r t s . F i g u r e s 1 3 and 14. a r e p h o t o g r a p h s of t h e f e n c e a t t h i s t i m e , D u r i n g F e b r u a r y , snow a c c u m u l a t e d on t h e open g r o u n d t o d e p t h s o f a p p r o x i m a t e l y

18

i n c h e s . F u r t h e r s a g g i n g o f t h e f e n c e t o o k p l a c e . A n o t h e r f a i l u r e o c c u r r e d a t one o f t h e a n c h o r p o i n t s i n t h e l i g h t - w e i g h t c r e o s o t e - i m p r e g n a t e d mesh, T h f s i s i l l u s t r a t e d

tiy t h e 3 h o t o g r a p h o f F i g u r e 1

:,

t a l i e n on F e t z u a r y 2 1 ,

l9:;O.

T i g u r e s

1 5 ,

1 7 a n d

18

a r e p h o t o g r a y h s o f t h e f i e l d i n s t a l l a t i o n on L:arch I/!, l $ s O . The e x c e s s i v e s a g between s u p p o r t s i s c l e a r l y il- l u s t r a t e d .

The snow h a d n e a r l y d i s a p p e a r e d by hiarch 30. The f e n c e was removed s h o r t l y a f t e r t h i s d a t e . F i g u r e s 1 9 , 20 a n d 2 1 a r e

photo4;raphs o f t h e f e n c e on d e p l e t i o n o f t h e snow c o v e r . The l i g h t - w e i g h t c r e o s o t e - i n ~ p r e g n a t e d rnesh showed tile g r e a t e s t d e t e r i o r a t i o n w h i l e t h e h e a v y - w e i g h t c r e o s o t e - - i m p r e g n a t e d n e ~ h showed

rn

d e t e r i o - r a t i o n s a v e a s a g . ( s e e F i g u r e 2 1 ) . Soon a f t e r r e m o v a l o f t h e f e n c e , s u i t a t l e s p e c i m e n f i t r e s were o k t . a i n e d f o r t e n s i l e s t r e n g t k t e s t s . ( i i ) L a t o r a t o r y 'I1ests _.-

_---

( a ) T e m p e r a t u r e C y c l i n g T e s t s T h e s e t e s t s werBe c a r r i e d on t h r o u g h o u t t h e o p e r a t i n g d a y o f t h e r e f r i g e r a t i o n ~ l a n t f o r s e v e n d a y s . The d a i l y t e m p e r a t u r e r e c o r d s a r e g i v e n i n F i f ; u r e 3. Yo damage c o u l d be v i s u a l l y o b ~ e r v e d on c o m p l e t i o n o f t h e t e s t s . Thus, f f ' c r e t e r , s i l e s t r e n g t h was t h e s o l e i n d i c a t o r o f d e t e r i o r a t i o n . An i n t e r e s t i r l g o b s e r v a t i o n o f t ' n e ~ e *samples w a s o b t a i n e d p r i o r t o t h e i c i n s t e s t s . The mounted s a m p l e s were k e p t i n a c o l d c h a m i e r t e t v i e e n t e s t s . A t one t.irne tihe t e r r ; p e r a t u r e was a l l o w e d t o d r o p to - 6 0 " ~ . _{f o r s e v e r a l hour^. The p a r a f f i n - i n p r e g n a t e d mesh}

v!as e x t r e - t n e l y b r i t t l e a t this t e n l p e r a t u r e . I t c o u l d e a s i l y be c r a c k e d by a s h a r p blow .l. illhe heavy-we i6;ht c r e o s o t e - i n i - p r e g n a t e d nesh was a l s o q u i t e s t i f f , but. v1ould n o t f r a c t u r e . Sy c o n t r a s t , t h e l i g h t - w e i ~ i h t c r e o s o t e - i m p r e ~ r a t e d mesh was q u i t e p 1 i a t : l e a t t h i s t e m p e r a t u r e . Hcwever, when t h e t e m p e r a t u ~ e re t u r n e d t o 2 G ° F . t h e b r i t t l e c h a r a c t e r i s t i c s o f t h e two s a m p l e s c o m p l e t e l y d i s a p p e a r e d . ( b ) I c i n g T e s t s The s a m p l e s were h e a v i l y f c e d a s i l l u s t r a t e d i n F i g u r e s

5

a n d

6 .

5 h a r p t,lows t o t h e mesh i n t h i s c o n d i t i o n p r o d u c e d n o f ~ a c t u r e . The i c e was m e r e l y b r o k e n o f f t h e mesh, t h u s i n d i c a t i n g a d e s i r a b l e low a d h e s i o n v a l u e . No deterioration c o u l d Le o t s e r v e d a f t e r t h e i c e h a d been a l l o w e d t o m e l t ,

( c ) Wind T u n n e l T e s t s

T a b l e I i s a t a t . l u l a t f o n o f t h e v a r i o u s e x p e r i m e n t a l q u a n t f t i e s o f t h i s t e s t .

I t m u s t be r e a l f z e d t h a t t h e e x p e r i m e n t a l c o n d i t i o n s were e x c e e d i n g l y s e v e r e . The w a t e r r a a t e employed i s e q u i v a l e n t t o f i v e i n c h e s o f p r e c i g i t a t i o n p e r h o u r . A s i n t h e o t h e r t e ~ . t s no damage c o u l d be o b s e r v e d v i s u a i l y

.

( d ) F i b r e T e n s i o n Tests Twelve p e p r a e s e n t a t i v e f i b r e s a p p r o x i m a t e l y 1 2 i n c h e s i n l e n e t h f r o m e a c h sacnple were l o a d e d t o f a i l u r e . 7,ix o f t h e s p e c f - mens were s e l e c t e d from f i b r e s p e r p e n d i c u l a r t o t h e m a r g i n w i r e and

s i x f r o n ~ f i t r e s p a r a l l e l t o i t ; , The' f i t r e s were t e s t e d by t h e S t r u c t u r e s Cec t f o n o f t h e D i v i s f o n o f Ivlechanical E n g i n e e r i n g and t h e T e x t i l e s t ; e c t i o n o f t h e D - i v i s i o n o f A p p l i e d C h e m i s t r y of t h e N a t i o n a l R e s e a r c h C o u n c i L . The i m p o r t a n t r e s u l t i s t h a t c o n s i d e r i n g t h e s c a t t e r w i t h - i n a s i m i l a r g r o u p of s p e c i m e n s , no a p p r e c i a b l e d e c r e a s e o f t e n s i l e s t r e n g t h was p r o d u c e d ky a n y o f t h e t e s t s p e r f o r m e d . T a t l e 2 i s a resume o f t h e t e s t ~ e s u l t s . The rcost i m p o r t a n t f e a t u r e o f t h e e n t i r e s e r i e s o f t e s t s was t h e l a c k o f d e c r e a r e o f t e n s l l e s t r e n g t h o f t h e f i b r e s u n d e r t h e rrany s e v e r e c o n d i t i c 3 n s i m p o s e d , Low t e m p e r a t u r e , r a i n a n d snow a l o n e a p p e a r e d t o h a v e l i t t l e d e t e r i o r a t i n g e f f e c t . S t r o n g w i n d s were t h e one n a t u r a l p';enomenon c a u s i n g e x c e s s i v e damage. I t a p - p e a r e d t h a t h i g h l o c a l s t r e s s c o n c e n t r a t i o n s a t t h e a n c h o r p o i n t s were t h e c h i e f c a u s e o f f a i l u r e .

Due t o r e s t r f c t e d s i z e o f t h e s a m p l e s f o r t h e wind t u n n e l t e s t s no wind d a ~ a g e o c @ u r p e d . I t a p p e a r s , h o w e v e r , t h a t r i g i d m o u n t i n g t e n d s t o m i n i m i z e wfnd e f f e c t s , S p a c i n g t h e a n c h o r p o s t s a t c l o s e r t h a n t h e

15

f e e t between c e n t r e s employed h e r e may f u r t h e r t e n d t o r e d u c e wind e f f e c t s , a s I t would impose l e s s l o a d on e a c h i n d f vf d u a l p o s t . F u r t h e r m o r e , t h f s woul d a l s o t e n d t o minim1 z e s a g g i n g b e t w e e n t h e s u p p o r t s L A d d i t i o n a l t e s t s s h o u l d t e c a r r i e d o u t t o d e t e r m i n e t h e k e e p i n g q u a l i t i e s d u r i n g s t o r a g e .

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1950

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5

Creosote-impregneted paper-mesh snow f e n c e on corn-

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Paper-me sh anow fence sample on completion of r ta st In $he icing r%md t m e l k .

P i g . 11

Failure of paper-mesh snow fsaoe st

Fig. 12

Paper mesh ansa f e n c e J a n .

16,

1950.

P a p e r mesh snow fence

Jan.

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1958.

Paper mesh snow fence Jan. 19, 1950.

P f g B

15

Fsf l u ~ e o f %he paper-me eh snow f e n c e , Feb. 21, lqS6,

Paper-m~sh snow f e n c e , Hareh 14,

1950

F i g . 2 8

Paper mesh snow fence

Xareh 30, 1$58.

F i g . 21

Faper mesh snow fence