Loading tests on box lintels

Publisher’s version / Version de l'éditeur:

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 PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca.

Questions? Contact the NRC Publications Archive team at

PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information.

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.

Internal Report (National Research Council of Canada. Division of Building

Research), 1964-09-01

READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE.

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

NRC Publications Archive Record / Notice des Archives des publications du CNRC : https://nrc-publications.canada.ca/eng/view/object/?id=bf2dbc18-1a93-47e8-8206-e2f4233763d6 https://publications-cnrc.canada.ca/fra/voir/objet/?id=bf2dbc18-1a93-47e8-8206-e2f4233763d6

NRC Publications Archive

Archives des publications du CNRC

For the publisher’s version, please access the DOI link below./ Pour consulter la version de l’éditeur, utilisez le lien DOI ci-dessous.

https://doi.org/10.4224/20337841

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

Loading tests on box lintels

NATIONAL RESEARCH COUNCIL CANADA

DIVISION O F BUILDING RESEARCH

LOADING TESTS ON BOX LINTELS

by

B. G. W. P e t e r I n t e r n a l R e p o r t No.

297

of t h e Division of Building R e s e a r c h OTTAWA S e p t e m b e r

1964

PREFACE

The Division of Building R e s e a r c h h a s devoted consider

-

able attention t o methods of improving wood-frame construction a s well a s finding ways of making t h i s type of construction m o r e

economical where t h i s i s possible with p r o p e r r e g a r d t o the r e q u i r e d s t r u c t u r a l p e r f o r m a n c e .

One idea providing potential economies i n wood-frame construction c o n s i s t s in replacing solid wood l i n t e l s over window and door openings in walls by hollow box l i n t e l s which mobilize the strength of the wall covering. T h i s s y s t e m was t r i e d out in t h e M a r k

I1

and Mark I11 demonstration houses of the National House Builder s As sociation.

It was a t the suggestion of the NHBA that the work described in this r e p o r t was c a r r i e d out, with the a i m of indicating load-carrying capacities and deflections of box lintels using gypsum board and plywood coverings, over a range of spans. Two load conditions w e r e considered: that over an opening in an e x t e r i o r wall, supporting roof r a f t e r s subjected t o snow load, and that in an i n t e r i o r wall, supporting ceiling and a t t i c loads only.

The r e p o r t was p r e p a r e d by B. G. W. P e t e r , a r e s e a r c h officer in t h e Building S t r u c t u r e s Section in c l o s e cooperation with m e m b e r s of the Housing Section.

Ottawa

September 1964

R. F. Legget, Director.

LOADING TESTS ON BOX LINTELS

B.

G.

W. P e t e r

T h e Housing S t a n d a r d s of Canada (Supplement No. 5 t o t h e National Building Code of Canada, 1963) r e q u i r e t h a t openings in l o a d - b e a r i n g stud walls and p a r t i t i o n s b e b r i d g e d by l i n t e l s t o d i s t r i b u t e s u p e r i m p o s e d l o a d s t o t h e adjacent studs. Conventionally, t h e l i n t e l s have been solid wood b e a m s . Box b e a m s c o n s i s t i n g of 2 x 4 f l a n g e s and plywood o r gypsum b o a r d webs have b e e n p r o p o s e d a s an a l t e r n a t i v e t o t h e conventional solid wood l i n t e l s , s i n c e such box b e a m s m a y p r o v i d e potential e c o n o m i e s by mobilizing t h e s t r e n g t h of t h e w a l l c o v e r i n g s and t h u s m o r e efficient u s e of

m a t e r i a l . T h e s y s t e m w a s t r i e d out i n t h e National Home B u i l d e r s A s s o c i a t i o n t s M a r k I1 d e m o n s t r a t i o n h o u s e c o n s t r u c t e d in 1959 i n F o r e s t Lawn, A l b e r t a , and a g a i n in t h e M a r k I11 h o u s e built i n 1961 a t RCAF Station, Rockcliffe, Ontario. Following t h e s e t r i a l s t h e NHBA r e q u e s t e d t h e Division of Building R e s e a r c h t o i n v e s t i g a t e t h e adequacy of box b e a m l i n t e l s utilizing gypsum b o a r d and plywood s k i n s o v e r a r a n g e of s p a n s a s an a l t e r n a t i v e t o conventional f r a m i n g and t o develop t e s t information that could b e u s e d t o e v a l u a t e t h i s method of construction.

T h i s r e p o r t d e a l s with t h e loading t e s t s that w e r e con

-

ducted on two s e r i e s ( a pilot s e r i e s and a n a c c e p t a n c e p e r f o r m a n c e s e r i e s ) of box l i n t e l s t o d e t e r m i n e t h e i r l o a d - c a r r y i n g c a p a c i t y and deflection c h a r a c t e r i s t i c s . Two u s e s o r load conditions w e r e c o n - s i d e r e d , that of a n opening in a n e x t e r i o r wall, supporting roof r a f t e r s (snow load), and that in an i n t e r i o r wall (no snow load). DESCRIPTION O F LINTELS AND TEST METHOD

All t h e l i n t e l f r a m e s c o n s i s t e d of n o m i n a l 2 x 4 e a s t e r n s p r u c e for upper and lower c h o r d s with n o m i n a l 2 x

4

v e r t i c a l end m e m b e r s . T h e depth of a l l b e a m s w a s 12 in. while t h e spans v a r i e d f r o m 4 t o

8

ft. T o t h i s f r a m e t h e sheathing m a t e r i a l , e i t h e r plywood o r gypsum board, w a s n a i l e d with l $ -in. r i n g n a i l s s p a c e d a t 3 in. F o r s o m e 4-ft span e x t e r i o r l i n t e l s with plywood on both s i d e s , t h e nailing w a s changed t o 2$-in. common n a i l s , a l s o a t 3 -in. s p a c i n g s . In s o m e b e a m s , v e r t i c a l 2

x

4 c r i p p l e s t u d s w e r e u s e d a t 16-in.

c e n t r e s t o p r e v e n t buckling of t h e sheathing m a t e r i a l . Lintel d e s i g n s a r e shown in F i g u r e s 1, 2 and 3.

T h e l i n t e l s t e s t e d w e r e :

1. P i l o t S e r i e s

-

a ) 4-,

6 -

and 8-ft s p a n s with g y p s u m w a l l b o a r d on both s i d e s ( F i g u r e 1B).

b) 4-,

6 -

and 8 - f t s p a n s with plywood on both s i d e s ( F i g u r e s I A and 2B).

c) 6-ft s p a n with g y p s u m w a l l b o a r d on one s i d e a n d p l y - wood on t h e o t h e r ( F i g u r e

2C).

2. A c c e p t a n c e P e r f o r m a n c e S e r i e s

a ) I n t e r i o r l i n t e l s of 8-ft s p a n with plywood on both s i d e s a n d of 4-ft s p a n with gypsum b o a r d on both s i d e s

( F i g u r e s 1A and 1B).

b) E x t e r i o r l i n t e l s of 4- a n d 6-ft s p a n s with plywood on both s i d e s ( F i g u r e s 2B and 3).

T h e b e a m s w e r e s i m p l y s u p p o r t e d a t both e n d s by 1 i - by 1 i - b y 3 i - i n . hardwood b l o c k s , a n d loaded by two 2;-ton h y d r a u l i c j a c k s a t t h e q u a r t e r p o i n t s ( F i g u r e 4). F o r a l o n g - t e r m t e s t of 30 days, two b e a m s w e r e loaded with l e a d - f i l l e d b a g s ( F i g u r e 12),

M i d - s p a n d e f l e c t i o n s w e r e m e a s u r e d by m e a n s of a t a u t w i r e which e l i m i n a t e d e f f e c t s of s u p p o r t s e t t l e m e n t d u r i n g t h e t e s t . On e a c h s i d e , h o l e s w e r e cut i n t o t h e s h e a t h i n g m a t e r i a l a n d n a i l s d r i v e n i n t o t h e v e r t i c a l 2 x 4 end m e m b e r s . P i a n o w i r e s with weights a t t a c h e d w e r e s u s p e n d e d a c r o s s t h e s e n a i l s , and a g r a d u a t e d s c a l e w a s a t t a c h e d t o t h e s h e a t h i n g m a t e r i a l a t m i d - s p a n s o t h a t d e f l e c t i o n s of t h e m i d - s p a n w e r e m e a s u r e d r e l a t i v e t o t h e end s t i f f e n e r m e m b e r s . CONSIDERED PERFORMANCE REQUIREMENTS

In evaluating t h e p e r f o r m a n c e of t h e l i n t e l s , both

d e f l e c t i o n s and f a i l u r e l o a d s m u s t be t a k e n i n t o account. Lacking a n y s p e c i f i c m i n i m u m p e r f o r m a n c e r e q u i r e m e n t in t h e H o u s i n g S t a n d a r d s f o r s u c h e l e m e n t s of h o u s e c o n s t r u c t i o n as l i n t e l s , i t w a s thought t h a t l i n t e l s could t e n t a t i v e l y be c o n s i d e r e d t o h a v e r e a s o n a b l y s a t i s f a c t o r y p e r f o r m a n c e if t h e deflections a t m i d - s p a n c a u s e d by applying t h e d e s i g n l i v e load f o r 1 h r w a s l e s s t h a n 1/360 of t h e s p a n , a n d i f f a i l u r e did not o c c u r u n d e r t w i c e t h e d e s i g n l o a d (load f a c t o r of 2 ) , m a i n t a i n e d f o r 24 h r .

LOADS

The design loads w e r e based on a 28-ft-wide single- s t o r e y house with an attic not a c c e s s i b l e by s t a i r s in a 50-psf snow load a r e a , calculated a s follows:

Interior Lintels

Dead load ( j o i s t s ) 2 p s f Live load (attic) 10 psf

Ceiling

-

4 psf

Total

_-

16 psf

F o r 28-ft -wide house, load = 16

x

1 4 = 224 lb/ft. E x t e r i o r Lintels

Snow load 50 p s f

Dead load ( r a f t e r s )

6

p s f Dead load ( j o i s t s ) 2 p s f Live load (attic) 10 p s f

Ceiling

_-

4 psf

Total 72 p s f

_-

F o r 28 -ft-wide house, load = 72 x 14 = 1008 lb/ft. F o r the pilot s e r i e s , the b e a m s w e r e loaded t o failure in i n c r e m e n t s of 250 lb p e r jack. The r a t e of loading was 2 min p e r i n c r e m e n t , and mid-span deflection readings w e r e taken a t each increment. F o r the acceptance p e r f o r m a n c e s e r i e s , the b e a m s w e r e loaded a t the s a m e r a t e to their full design load with deflection

readings taken at intermediate steps. The design load was maintained for 1 h r with deflection readings taken a t 5 min and 1 h r . The b e a m s w e r e then loaded t o twice the design load for 24 h r , a f t e r which the load was i n c r e a s e d t o failure.

RESULTS P i l o t S e r i e s

Deflections.

-

The plywood-sheathed lintels had l e s s deflection for the s a m e loads than the gypsum-sheathed l i n t e l s ( F i g u r e 5). F o r use a s interior lintels, a l l the plywood and gypsum lintels had l e s s than 1/360 span deflections a t the design _- ioad. F o r u s e in exterior walls, however, a l l spans of both the 4-ft plywood and gypsum lintels exceeded 1/360 span deflections. A

F a i l u r e .

-

P r e c e d i n g c o m p l e t e f a i l u r e of t h e gypsum box l i n t e l s , tension c r a c k s in t h e sheathing due t o bending m o m e n t s t r e s s e s o c c u r r e d a t about 80 t o 90 p e r cent of the f a i l u r e load. With the plywood box lintels, however, f a i l u r e o c c u r r e d e i t h e r in t h e nailing o r by buckling of t h e plywood n e a r t h e s u p p o r t s , both of which a r e due t o s h e a r i n g f o r c e s . Web s t i f f e n e r s s p a c e d 16 in. o. c. w e r e added t o one 6-ft plywood lintel, but t h i s had no significant effect on t h e deflections o r f a i l u r e load. F o r i n t e r i o r loads, t h e 4-, 6 - and 8 -ft l i n t e l s of both plywood and gypsum deflected l e s s t h a n 1/360 of t h e span at design load and withstood twice t h e design load for 2 4 h r . F o r e x t e r i o r loads, however, only t h e 4-ft plywood l i n t e l w a s capable of withstanding t w i c e t h e design load f o r 24 h r . Lone

-T

e r m T e s t

The p u r p o s e of t h e l o n g - t e r m t e s t w a s t o s h e d s o m e light on t h e c r e e p p e r f o r m a n c e of gypsum l i n t e l s under l o n g - t e r m loading. R e s u l t s of a p a i r of 4-ft l i n t e l s t e s t e d f o r 30 days a t full design load indicated t h a t although c r e e p d o e s o c c u r , t h e r e i s l i t t l e c o n c e r n for t h e 4-ft l i n t e l s under i n t e r i o r l o a d s s i n c e t h e t o t a l deflection w a s only 0. 025 in. a f t e r 30 days. T h i s i s well belcw t h e 1/360 s p a n deflection of 0. 133 in. ( F i g u r e 6).

Acceptance P e r f o r m a n c e S e r i e s

I n t e r i o r Lintels.

-

T h e two t y p e s of l i n t e l s t e s t e d f o r i n t e r i o r u s e w e r e 8-ft plywood and 4-ft gypsum. Both of t h e s e deflected l e s s than 1/360 of t h e s p a n at design load and withstood twice t h e design load for 24 h r ( F i g u r e 7). A s u m m a r y of res!ilts i s p r e s e n t e d i n T a b l e 11.

E x t e r i o r Lintels.

-

F o r e x t e r i o r u s e , plywood l i n t e l s with spans of 6 and 4 ft w e r e t e s t e d . T h e designs shown in F i g u r e s _- 2A and B deflected m o r e than 1/360 of t h e s p a n a t design load and w e r e not a b l e t o support twice t h e design load f o r 24 h r . F a i l u r e of t h e plywood l i n t e l s r e s u l t e d f r o m w e a k n e s s of t h e nailing between

sheathing and the f r a m e . By i n c r e a s i n g t h e n a i l s i z e f r o m 1$ in. t o 2 i in. and a l s o by using *-in. p1.ywood webs ( F i g u r e 3), the s t i f f n e s s and s t r e n g t h w e r e c o n s i d e r a b l y i n c r e a s e d ( F i g u r e 7).

DISCUSSION O F RESULTS Gvmsum L i n t e l s

F a i l u r e of t h e gypsum l i n t e l s o c c u r r e d f r o m t e n s i l e s t r e s s e s due t o t h e bending m o m e n t s i n t h e gypsum w e b s of t h e box b e a m ( F i g u r e 10). T h e s t r e n g t h s of t h e gypsum p a n e l s would only be

i n c r e a s e d by the u s e of thicker gypsum but not by i n c r e a s e in nailing alone.

Using t h e r e s u l t s f r o m both the pilot s e r i e s and t h e acceptance t e s t s , the s h o r t - t e r m loads causing a deflection of 1/360 of the span and f a i l u r e w e r e plotted against span. ( F i g u r ~ 8 ) .

Plvwood Lintels

F a i l u r e of the plywood lintels ( F i g u r e 11) o c c u r r e d at considerably higher loads than the gypsum l i n t e l s ( F i g u r e 8 ) when the s a m e nailing was used for both. Since f a i l u r e o c c u r r e d in the

plywood f r o m shearing f o r c e s between the plywood webs and the f r a m e , increasing the nailing alone was sufficient t o i n c r e a s e t h e strength.

R e s u l t s w e r e plotted f r o m both the pilot s e r i e s and acceptance t e s t s indicating the load a t 1/360 span deflection and a t failure ( F i g u r e

9).

C r e e p

As stated previously, c r e e p of the 4-ft gypsum lintels under the one-month load was about 50 p e r cent of the initial s h o r t - t e r m deflection. T h i s could e a s i l y be t o l e r a t e d a s the s h o r t - t e r m

deflection was only about 10 per cent of the allowable 1/360 span deflection.

CONCLUDING RE MARKS

Loading t e s t s w e r e c a r r i e d out on box lintel beams, with gypsum board or plywood a s covering, t o determine t h e i r load- c a r r y i n g capacity and deflection c h a r a c t e r i s t i c s . The depth of a l l box lintel b e a m s was 12 in., and the spans v a r i e d f r o m 4 t o 8 ft. Two c a s e s w e r e considered: lintels for e x t e r i o r walls (ceiling, attic and snow load, totalling 7 2 psf) and lintels for i n t e r i o r p a r t i t i o n s (ceiling and a t t i c load only, totalling 16 psf).

In the initial o r "pilot series1' of t e s t s , t h e load producing a span deflection r a t i o of 1/360 and the f a i l u r e load w e r e determined (Table I), w h e r e a s in the "acceptance p e r f o r m a n c e s e r i e s " of t e s t s , the deflections a t 1 x Dead plus Live Load, 2 x Dead plus Live Load a s well a s the failure load w e r e obtained (Table 11).

T h e r e a r e at p r e s e n t no specified nor any generally

accepted c r i t e r i a for lintel strength when it i s determined by t e s t , a s i s the c a s e f o r roof t r u s s e s . In t h e s e t e s t s , t h e r e f o r e , the roof t r u s s

l o a d t e s t r e q u i r e m e n t s of t h e H o u s i n g S t a n d a r d s w e r e followed. W h e r e t h e r e q u i r e d l o a d f a c t o r ( r a t i o of f a i l u r e l o a d t o d e s i g n l o a d ) a n d t h e m a x i m u m a l l o w a b l e deflection a r e known, h o w e v e r , t h e m a x i m u m a l l o w a b l e s p a n of l i n t e l s c a n b e d e t e r m i n e d f r o m F i g u r e s

TABLE

I

SUMMARY O F TESTS NOS. 1-8

PILOT SERIES

1

(Nailing f o r a l l lintels: 17-in. r i n g n a i l s a t 3-in. spacing)

*

G

=

Gypsum Board

P =

Plywood

T e s t No.

1

2

3

4

5

6

7

8

Type

F i g . 1 B

Fig. 1A

Fig. 1B

Fig. 1A

Fig. 1B

Fig. 1A

Fig. 2C

Fig. 2A

Span ft

4

4

6

6

8

8

6

6

*

Covering

1 / 2 " ~

5f16"P

1 / 2 " ~

5/16"P

1 / 2 " ~

5/16"P

1/2"P,

1 / 2 " ~

5/161tP

Load a t 1/ 360

Span Deflection,

lbfft

N. A.

630

400

610

250

410

480

580

F a i l u r e Load,

lbfft

1250

2080

6 50

1420

480

880

1320

1440

-

r-

& & & &

G &

J

\ \ \ \ \ \ ur n r n r n u u u 10 u P P

2 2 2 2

k k k k a

2 2

4 4 0 0 0 o +I* a

_{Z Z}

0 0 0 0 3 a a a a m o m a

"

u cd

9

9

4 o m N 9 cd

asp

a M v,

",

4 4 4 4 4 4 '7 : : " I

2

!=! . k k

2 % 2 2 2 2

:

k_{c d}k_d k_d

2

cd KJ Q) - 0 - 0 Q ) - 0 a - 0

2 2

;

;'

f+

4

2 2

!=! 3 M M M 4 d' " r l " .rl .rl .rl

::

.rl 4 4 4 .d 3 KJ _.rl .rl .rl 4 u Ll K J K J K J - 4 KJ .rl rn W d " d " 0 0

-

..

-

"

- E

k k k k c d c d K J a K J c a a Q )

_.9

2

_.y

H

$ l $ i 6 H * Z

Q)

-

k - 0 & m 0 0 0 0 0 0 0 0 0 0 0 0

2

KJ " 0 ' 9 4 0 0 00 00 d ' N 9 0 ' N m 9 0 ' 1 + 9 9 0 4 4 4 4 4 4 N N N N N 00 f- 0' rr) N 1 % I 0 0 0 I I I l m m l

.

.

.

.

0 0 0 0 0 0 0 9 4 N N I 4 I d' 0 0 d' 0 0 N I I I 0 0 ' 9 O 4 0 0

.

0

.

0 0 0 0

. . .

0 0 9 " " N N d' 0' d ' d ' o a m I 4

_.

4 r

_.

r

_,

) O

_.

0 0 4 1 ,

. . .

+ 4 d 0 4 0 0 0 0 0 0 0 0 3 0 0 0 9 0 rr) rr) 9 0 rr) rr) N =

=

N 4

-

-

-

-

I = = = = =

6

0

.

0

.

0 d' O d '

-

0 N =

=

N

-

-

I = -

- - - -

- - -0 N 0 Ll k E : C d' N k

.s

E

ul

.

.s

,

2

0 .rl Q)

a

4 4 0

9 5

rr)

3

! = ! . M a & .rl m KJ -0 Id 0 4

.Y

,"

a

Z K J C $ 4 d

.Y

:

a

4 - - M G .r( k

:

0 U Pt Pt

u

-

-

-

PC

-

Pt Pt Pt

-

-

-

-

- - -

-

' = = < <

=

-

-

9 % G N 4 4 4 : \ A \

'3;

'=;

4 3 4

4

4

-

-

a a

N 4

-

-

4

N

4 a u

r r ) m r r )

-

-

bi) bi)

-

-

b i )

& & & -

-

H

G

G

G

iZ G

G

5

a

*

u

"

d

c z

-

-

_-

- -

_-

=

=

oI 0I

-

-

-

-

-

-

-

= I t = = = = a 9 d' 26 -x 4 N r r ) d ' m 9 f- 4 4 4 4 4 4 4 " ( r O 4 N r r ) d ' 4 4 N N N N N

5116" Plywood

3"

Gypsum

1:

"

Ring Nails at 3'' o.

c.

1

F I G U R E 1

SPAN

4

-

-

l "

Plywo~d

-

it A

Stiffeners

I

I

TYPE A

TYPE

B

1

_{TYPE A}

_TYPE

_B

_{TYPE C}

23"

Common Nails at

3"

o.

c.

,

4" Plywood

5116" Plyildood

4"

Plvwood

-

3

Stiffeners

at 16"

I I

F I G U R E 3

0a 3704 - l

I

-

SPAN

L l NTEL T Y P E S

0

0.1 0.2 0.3

0.4 0.5

D E F L E C T I O N ,

I N.

I

I

I

I

6 ' Span

-

0

0.1 0.2 0. 3 0.4

D E F L E C T I OW, I N .

0

0

0.1 0.2 0.3 0.4

D E F L E C T I ON,

I

N.

I

I

I +

-

8'

Span

-

F I G U R E

5

Test

2

Test

3,4, &

7

Test

5 & 6

P I L O T S E R I E S , M I D S P A N

D E F L E C T I O N S ( D i a l G a u g e )

0L

I I I I

I

5

MIN

1 HR 1 DAY 10 DAYS

30

DAYS

0.05

2

_0.04 Z 0

-

0.03

W -1 F I G U R E

6

1 I I I 4 ' S p a n

-

-

-

-

D E F L E C T 1 O N T I M E C U R V E F O R L O N G T E R M 'TEST. G y p s u m

I

n t e r i o r L i n t e l s , L o a d 224 L b l F t (1 D.

L.

BQ 3 2 0 4 - 4

t

at

span Lintel Test 12 & 13

:

11360 Span 0 0.1 0.2 0.3 0.4 0.5 D E F L E C T I ON, I N. D E F L E C T I ON, I N . Plywood

,

1400 Exterior kk Lintel

y

1200

0

loo0 Test 14 0 800 I I I I

-

4 ' Span

-

I I

-

-

I 0 0.1 0.2 0.3 0.4 0.5 D E F L E C T I ON, I N . 1 I I I I I 2 Design Load _{4' Span}

_-

24" Nails

B

1

D.

L.

-

;

-

-

-

I I 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 D E F L E C T I O N ,

I

N . Gypsum

l

nterior Lintel Test 15, 16 & 17 Plywood Exterior Lintel Test 18, 22, 23, 24 F I G U R E 7 M I D S P A N D E F L E C T I O N S BR 3 2 0 4 - 5

L O A D S FOR

11360

S P A N D E F L E C T I O N S A N D F A I L U R E

OF G Y P S U M L I N T E L S

9

2000

1800

1600

I-

1400

LL. \

1200

1

-

1000

cZ

0

800

600

400

0-

0

1

2

3

4

5

6

7

8

9

10

S P A N , FT

I

I

I

I

I

I

I

I

I

I

L

-

2

Design Load

-

Exterior

-

-

o

NAl Ll NG

-

_1)"

_{Ring Nails at}

₃

in.

-

-

-

-

-

ni D. L.

-

Exterior

-

-

-

-

X 2 D . L

-

I

nterior

-

,,a1

D.L.

-

I

nterior

I

I

I

I

I

I

I

I

I

I

I

I

1

I

I

I

I

I

I

-

-

2

Design Load

\O

\

N A l Ll NG

-

Exterior

If"

Ring Nails at 3 in.

-

-

-

-

-

-

Fai

111

r e

-

-

_{11360 Span}

1

D. L.

Deflection

-

Exterior

-

-

_-

,o

2 D. L.

-

I nterior

.\

-

v l

D . L .

-

l

nterior

-

I

I

I

I

I

I

I

I

I

I

S P A N , F T

F I G U R E

9

L O A D S A T 1 / 3 6 0 S P A N D E F L E C T I O N A N D F A 1 L U R E

F O R P L Y W O O D L I N T E L S

F i g u r e 1 0 T y p i c a l 1nilu.r e oi' gypsum sheathed l i n t e l , T e n s i l e s t r e s s e s u u e t o b e n d i n g ~;lol~-ten& c a u s e d c r a c k i n g of w e b s .

F i g u r e I 1 Typical f a i l u r e of p l y w o o d s h e a t h e d lintel. Shear s t r e s s e s