Effect of Plan Configuration on Seismic Performance of Single-Story Wood-Frame Dwellings

Abstract

A numerical investigation is presented on effects of plan configuration on seismic responses of single-story, wood-frame dwellings. 151 models were developed using observations of 412 dwellings of rectangular, L, T, U, and Z-shapes in Oregon. A nonlinear, time-history program, Seismic Analysis Package for Wood-frame Structures, was the analysis platform. Models were analyzed for 10 pairs of biaxial ground motions (spectral accelerations from 0.1 g to 2.0 g) for Seattle. Configuration comparisons were made using median shear wall maximum drifts and occurrences of maximum drifts exceeding the 3% collapse prevention limit. Plan configuration significantly affects performance through building mass, lateral stiffnesses, and eccentricities. Irregular configuration tends to induce eccentricity and cause one wall to exceed the allowable drift limit, and fail, earlier than others. Square-like buildings usually perform better than long, thin rectangles. Classification of single-story dwellings based on shape parameters, including size and overall aspect ratio, plan shape, and percent cutoff area, can organize a building population into groups having similar performance and be a basis for including plan configuration in rapid visual screening.