Distributed yielding concept for improved seismic collapse performance of rigid wall-flexible diaphragm buildings

Rigid wall-flexible diaphragm (RWFD) buildings are a common type of single-story construction in North America, Europe, and New Zealand that incorporate rigid in-plane concrete or masonry walls and flexible in-plane wood, steel, or hybrid roof diaphragms. RWFD buildings have shown poor seismic performance during past earthquake events. In particular, it has been observed that the global seismic response is dominated by the response of the diaphragm, which is mainly attributed to large in-plane diaphragm displacements that significantly exceed the displacements of in-plane walls. In this study, the concept of distributed yielding in the flexible diaphragm by weakening certain intermediate diaphragm zones is explored as a cost-effective means to improve the seismic collapse capacity of RWFD buildings and mitigate their seismic vulnerability. A two-dimensional numerical framework was developed specifically for analyzing RWFD buildings and was used to evaluate the proposed concept. Results of nonlinear dynamic time-history response analyses conducted on a typical RWFD building incorporating a wood roof diaphragm show that distributing the inelastic response of the flexible diaphragm along its span is beneficial to the seismic collapse capacity of RWFD buildings. A seismic design approach based on this concept is also formulated.