2001 ASD Supplements - unprotected PDF - American Wood Council

SP-38SUPPLEMENTAL DESIGN ASSISTANCEwb120FbS=l 12120 ( 640×1.2)=224= 160 psfShear Strength in the PlaneFrom Table 3.3, a single floor 24 oc panel with stressapplied parallel to the strength axis has shear strength inthe plane (F S [Ib/Q]) equal to 250 lb./ft. This capacity isadjusted by a C G factor of 1.0 as shown in Table 3.3.1 forCOM-PLY.( I )20 Fsb/Qws=l220 250 x 10=( )( 24 −1.5)= 222 psfBending StiffnessFrom Table 3.1, a single floor 24 oc panel with stressapplied parallel to the strength axis has a dry stiffness capacity(EI) of 300,000 lb.-in. 2 /ft. This capacity is adjustedby a C Gfactor of 1.1 as shown in Table 3.1.1 for COM-PLY. The deflection limit for live load is l/360.wl3∆ =1,743 EIw41. 0 ( 24− 1. 5+0. 25)=1, 743( 300, 000×1. 1)−4= 4.657×10 in.d∆all24/360= =∆ 4.657×104−4= 143 psfWhile the above calculations would indicate that thissingle floor construction has a live load capacity of 143psf (limited by bending stiffness), it is important to notethat some structural panel applications are not controlledby uniform load. Residential floors, commonly designedfor 40 psf live load, are a good example. The calculatedallowable load is greatly in excess of the typical designload.This excess does not mean that floor spans for singlefloor panels can be increased, but only that there is considerablereserve strength and stiffness for uniform loads.Recommended maximum spans for structural panel floorsare based on deflection under concentrated loads, how the“floor” responds to passing foot traffic, and other subjectivefactors which relate to user acceptance. Always checkthe maximum floor and roof spans for structural panelsbefore making a final selection for these applications.APA – The Engineered Wood Association