Seismic Fragility Analysis of Nepalese Brick-Timber Heritage Structures under Near-Fault Pulse-Like Ground Motions

To study the influence of near-fault pulse-like ground motions on the seismic performance of masonry-timber heritage structures in Nepal, a two-storey Nepalese masonry-timber structure was selected as a prototype according to the typical seismic damage mode in the Gorkha earthquake. A numerical simulation was established by means of the equivalent-frame model. The peak ground accelerations and inter-storey drift were used as indexes for ground motion intensity and the structural damage, respectively; subsequently, the IDA (incremental dynamic analysis) method was used to determine the ultimate states. Additionally, the seismic fragility curves of the structure subjected to pulse-like and non-pulse-like ground motions were compared. The results indicate that the inter-storey drift corresponding to the immediate occupancy state, life safety state, and collapse prevention state are 0.06%, 0.32%, and 0.44%, respectively. Although it is prone to the immediate occupancy state of the structures according to the damage probability curves, the probability of reaching the life safety state or collapse prevention state is relatively low.However, as the limit of life safety state is reached or exceeded, a slight PGA increment could lead to structural collapse. Further, with respect to the case experiencing non-pulse-like ground motions, the damage probabilities for immediate occupancy state, life safety state, and collapse prevention are to 18.9%, 14.3%, and 12.6% higher than the pulse-like ground motion case, respectively. In addition, due to the sensitivity of Nepalese masonry-timber heritage structures, the effect of pulse-like ground motions should be considered in practical reconstruction and retrofitting projects.