AWS EDITION 1, 2009

580

Appendix B

© 2009, AWI, AWMAC, WI - Architectural Woodwork Standards - 1st Edition, October 1, 2009

(Appendix B is not part of the AWS for compliance purposes)

SHELF DEFLECTION INFORMATION

The Department of Wood Science in the Division of Forestry at West Virginia University, conducted

a study for the Architectural Woodwork Institute regarding the deflection of wood shelving materials

under various amount of stress. The following table represents their findings with the various

products tested. The study was developed in the inch-pound method and is not converted to

metric for this example.

The table shows total uniformly distributed load requirements necessary to cause deflection of

(^1) /
4 inch in shelves 8 and 12 inches wide with spans (i.e., unfixed, supported at each end) of 30, 36,
42, and 48 inches. Load required to deflect shelves more or less than^1 / 4 inch may be estimated
by direct proportion. For example, the uniformly distributed load required to cause a deflection
of^1 / 8 inch is one-half that of the value in the table. For widths different than 8 or 12 inches (the
values used in the table), load required to cause a^1 / 4 inch deflection may also be determined by
direct proportion. A 6 inch wide shelf, for example, will deflect twice as much as a 12 inch wide
shelf under the same load.
The following equation shows how deflection is related to shelf dimensions, width, thickness, span,
load per inch of span and E-value, a material property which measures stiffness or resistance
to deflection. The higher the E-value, the less the deflection. When a shelf is made with several
materials, each with its own E-value, a composite E-value must be determined.
Shelf Deflection of^1 / 4 ” by Estimated Total Distributed Load in Pounds
Msaterial Thicknes
S"pan 3" 0 3" 6 4" 2 48
W"idth 8"1" 2 8"1" 2 8"1" 2 8" 12
Yellow-Poplar
lumber

3 / 4 "

1 - 1 / 16 "

322

lbs.

912

483

lbs.

1368

189

lbs.

528

284

lbs.

790

117

lbs.

332

175

lbs.

498

78

lbs.

221

117

lbs.

332

RedGum

SweetGum

HardMaple

lumber

3 / 4 "

1 - 1 / 16 "

356

lbs.

1021

534

lbs.

1536

209

lbs.

592

313

lbs.

888

133

lbs.

373

206

lbs.

560

88

lbs.

249

133

lbs.

374

Pecan

RedOak

Birch

lumber 13 - /^41 /" 16 " 1410304 1670001 623602 934908 414146 261291 29787 414156

Hickory

Mediumdensityparticleboard

(raworcoveredwith"melamine")

3 / 4 "

1 "

78

185

117

277

46

109

69

164

29

69

43

102

19

45

28

66

Mediumdensityfiberboard

(raworcoveredwith"melamine")

3 / 4 "

1 "

100

237

150

356

58

137

87

206

36

85

54

128

25

59

38

90

B"irchfacedplywood,veneercore 35 / 4 184 261 89142 5186345

Birchfacedplywood,mediumdensity

particleboardcore^35 /^4 "^182128791604861364

Mediumdensityparticleboardcoveredtwo

sidesandoneedgewithnominal 0. 028 "

highpressuredecorativelaminate

3 / 4 "

(core)^11742061901436692436

Mediumdensityparticleboardcoveredtwo

sidesandoneedgewithnominal 0. 050 "

highpressuredecorativelaminate

3 / 4 "

(core)^203437515326089182578

Mediumdensityparticleboardwith 1 / 8 "

solidlumberedge^39 /^4 "^8913359733052233

Mediumdensityparticleboardwith 3 / 4 "

solidlumberedge^30 /^4 "^10010560924365283

Mediumdensityparticleboardwith 3 / 4 "x 1 -

1 / 2 "solidlumberdroppededge^34 /^4 "^3584632112241231259710

NOTE:AllmediumdensityparticleboardisANSI 208. 1 - (ltest edition), Type M-2

Theinformationandratingsstatedherepertaintomaterialcurrentlyofferedandrepresentresultsoftestsbelievedtobe

reliable.However,duetovariationsinhandlingandinmethodsnotknownorunderourcontrol,no warantee or

guarantee as to the end results can be made.

10 - Casework

To compute deflection:

D=0.1563wl

4

Ebh^3

In which the values are:

D = deflection (in inches)

w = load per lineal inch of span

l = span (length)

E = modulus of elasticity

b = base (width)

h = depth (thickness)

B