Strength-Based Reliability of Wood Shearwalls Subject to Wind Load

Wood shearwalls provide the majority of the lateral force resistance in light-frame wood construction, which makes up the vast percentage of residential and some percentage of commercial construction in the United States. One of the objectives of a recent Structural Engineering Institute (SEI) special project entitled "Reevaluation of LRFD for engineered wood products: Keeping pace with changes in ASCE 7" was to evaluate the reliability of wood shearwalls designed using AF&PA/ASCE 16. This technical note describes the evaluation procedure and presents results from an analysis of wood shearwalls subject to wind load considering the ultimate strength (capacity) limit state. In addition to ultimate capacity, statistical distributions of the deformations at ultimate capacity were determined. The resistance of each wall was determined from a monotonic pushover analysis, which uses existing load-slip fastener data to determine the monotonic behavior of a wood shearwall. The wind load statistics were determined as a function of the nominal (code-specified) values using existing load models. Reliability indices for wood shearwalls built using 8d common nails [3.3  mm (0.131  in.) diameter] and subject to the 50  year design wind load ranged from (beta)= 3 to 3.5. The percent drift at ultimate (neglecting uplift) ranged from 1.6 to 2%.