2001 ASD Supplements - unprotected PDF - American Wood Council

SW-14SHEAR WALLS4.1 GeneralA shear wall behaves similar to a horizontal diaphragm.In fact, a shear wall is simply a cantilevereddiaphragm to which load is applied at the top of the walland is transferred to the foundation along the bottom ofthe wall. This creates a potential for overturning whichmust be accounted for, and any over-turning force is typicallyresisted by hold-downs, or tension ties, at each endof the shear wall segments.Tables 4.1A and 4.1B present the tabulated values forwood structural panel sheathed wood frame shear wallsfor wind loading and seismic loading, respectively. Somemodel building codes have adopted a 40% increase forallowable shear wall resistance when subjected to windloading. For the convenience of the user of this Supplement,Table 4.1A reflects the 40% increase that may bepermissible. The designer should confirm that the increaseis applicable under the local code; if notapplicable, use Table 4.1B. The basis for the increase isa change in design philosophy for estimating wind forces.In addition, the increase helps to account for better understandingof wind loads and the historical excellentperformance of shear walls subjected to high wind events.4.2 Using Shear Wall TablesExample One:Given:• commercial building• wind loading• wall requires 5/8-inch gypsum sheathing on the exteriorof the building for 1-hour fire separation• required shear wall capacity is 670 lb./ft.Find:Panel thickness, nail size and nailing scheduleSolution:Ensure that the locally accepted building code allowsthe 40% increase for wind load incorporated in Table 4.1A.Using Table 4.1A, check the “Panels applied over 1/2- inchor 5/8-inch gypsum sheathing” area of table. Check“SHEATHING…” rows first since Structural I may notbe readily available in all areas. From the table, see that10d nails with a 3- and 12-in. nail spacing and any thicknessof Sheathing will provide a capacity of 685 lb./ft.provided that the framing at adjoining panel edges is 3-inchnominal or wider. As 685 lb./ft. is greater than 670 lb./ft.,this selection is OK for use.Example Two:Given:• residential building• seismic loading• typical wall sheathing thickness of 7/16 inch• typical nail size of 8d common• wall stud spacing of 24 inches oc.• required shear wall capacity is 435 lb./in.Find:Required nail spacingSolution:Using Table 4.1B, check the “Panels applied direct toframing” area of table. Check “SHEATHING…” rows firstbecause Structural I may not be readily available in allareas. From the table, see that 7/16-inch structural-usepanels, 8d nails with a 3- and 6-in. nail spacing (see footnoteb) will provide a capacity of 450 lb./ft. As 450 lb./ft.is greater than 435 lb./ft., this selection is OK for use.APA – The Engineered Wood Association