Effects of ground motion duration on the seismic performance and collapse capacity of timber structures

This thesis describes the performance of timber structures under long duration earthquakes. The primary objective of this study is to quantify the effects of long duration ground shaking on wood structures compared to short duration shaking. The investigation is confined to conventional low-rise and modern mid-rise woodframe buildings. Full scale models of the benchmark structures used for this investigation were also constructed and tested on shake tables. Three-dimensional numerical models of the structures were developed using the Timber3D program and validated with the shake table test data. To isolate the effects of duration, two sets of short and long duration records that had approximately the same response spectra were used for nonlinear dynamic analyses of the model structures. Their collapse capacity was evaluated using fragility curves developed by incremental dynamic analysis. The results showed the collapse rate increased under long duration shaking due to a large number of inelastic cycles and higher cumulative energy demands that timber structures experienced compare with the short duration motions. The reduction in median collapse capacity for the low-rise wood structure with engineered oriented strand board (OSB) sheathing and stucco was 26%, for the same structure but without stucco was 29%, and for structure with horizontal board sheathings was 61%, respectively. The reduction in median collapse capacity for the mid-rise woodframe structure was 18%. These results suggest that current design practice based on the response spectra analysis may not adequately characterize the potential collapse of timber structures. This study highlights the need to include ground motion duration effects into current seismic design and assessment provisions.Applied Science, Faculty ofCivil Engineering, Department ofGraduat