Question

Estimate the amount of shrinkage that will occur in the depth of the 4 x 14 sawn lumber beam in Figure 4.A. Use the simplified shrinkage approach recom- mended in Ref. 4.26. Assume an initial moisture content of 19 percent and a final MC of 10 percent ROOF SHEATHING SET TOP OF GREEN ROOF BEAMS ABOVE TOP OF GIRDER TO ALLOW FOR SHRINKAGE 13.25" METAL HANGER 4x 14 SAWN LUMBER ROOF BEAM GIRDER Top of roof beams set higher for shrinkage. FIGURE 4.A NOTE: The top of the wood beams should be set higher than the top of the girder by an amount equal to the estimated shrinkage. After shrinkage, the roof sheath- ing will be supported by beams and girders that are all at the same elevation. Without this allowance for shrinkage, a wave or bump may be created in the sheathing where it passes over the girder.

Answer 1

L Solution in Dimension of beams Width = 13.25! Initial moisture content = 19%. final moisture content = 10%. Speces - Sawn lumber (Hickores) (river) Now using Wisconsin formuldi- S = (MI-MA) XD (30 – 30 + MI where S=Shrinkage in inches me = Initial maistre content Mr = final moisture content b = Dimension at initial 30= fibre Saturation point ST- total tangential shrinkage So total radial shrinkage. Hence from above formules :- MI = 19 ; ME= 10; D = 13.25" ST=1.0 (For History species used in Morthus) SR i 7-8 Now pet all the data in equation &

- 0.455 inch (1970) X 15.25 119.25 261.72 30-30] +19 => [ST=0.455 inch Again use formula o =) S= (1940) X13.25 = 119.25 -0.319 inch 130 -307419 373.6) Lo-078 SISI SR = 0.319 inch Hence shrinkage in tangential is (0.4555 I and shrinkage in radial is 10.319 inch