Seismic performance of timber buildings retrofitted with hybrid walls and impact-resilient isolators

Light-frame timber buildings (LFTBs) are widely used in seismic regions due to their ease of assembly and the availability of pre-qualified structural elements. However, LFTBs are susceptible to collapse mechanisms such as soft-story failures during extreme events. Different studies have focused on increasing the LFTB's lateral force-resisting system capacity to address this vulnerability by constructing hybrid elements combining wood with other materials. Although these hybrid buildings are more resistant to seismic forces, they have exhibited large floor accelerations. On the other hand, frictional seismic isolation has demonstrated its efficiency in protecting LFTBs and reducing their floor accelerations. However, during extreme earthquakes, an impact between the perimeter ring of the isolators and the sliders can occur, reducing the effectiveness of seismic isolation. In response to this phenomenon, this paper evaluates the seismic performance of archetype buildings, representative of the Chilean real estate sector, subjected to extreme ground motions capable of inducing impact. The analysis includes retrofitted LFTBs after incorporating hybrid walls and recently developed Impact-Resilient Double Concave Frictional Pendulum (IR-DCFP) bearings. Considering the isolators remain functional under extreme displacements and the FEMA P695 methodology, incremental dynamic analyses of nonlinear models were conducted to obtain the collapse margin ratio of each archetype and, subsequently, their fragility curves. Results indicated that incorporating hybrid walls and IR-DCFPs reduced the LFTB's probability of collapse at the Maximum Considered Earthquake level by up to 35 %, even considering a low wall density and the use of compact bearings. These findings suggest that IR-DCFPs combined with hybrid walls offer a cost-effective solution for improving the seismic resilience of LFTBs in high-seismicity regions.