Effect of seismic sequence on the shophouses at Parapat city

The threat of an earthquake on a site was not a single earthquake event during the building’s life span built at that site. The earthquake sourced from one or two faults surrounding the area would frequently occur during a period. The effect of this seismic sequence was essential to be studied, particularly on the shophouse building that rapid growth in developing countries in Asia. The shophouse was mainly built without the technical design by the civil engineer. Therefore, this study aimed to define the shophouse’s story drift and collapse pattern under the influence of seismic sequence. The study selected Parapat City as the shophouse since the city was built at the lakeside of Toba Caldera (one of the most excellent calderas in the world). Three types of the 2-story shophouse were considered in this study, which was different in the number of the front door. The seismic sequence records were selected based on source-to-site distance, fault mechanism, magnitude, and size class and, thus, scale to the design spectrum for Parapat City. The study conducted the nonlinear inelastic response history analyses up to the collapse stage. It concluded that the weak direction was in the sideway direction of shophouses. Therefore, the more significant drift was mainly occurred in this direction compared with the forward-backward focus. These drifts were especially causing the plastic hinge development on the shophouse structures. This study has explained that the strong story stiffness direction could be the direction of the soft story collapse due to the random vibration of the earthquake. The soft-story type of collapse is found as the collapse pattern of all shophouses.