Seismic Vulnerability Assessment of RC Frame Buildings Designed Using the DDBD Approach: A Parametric Study

Direct displacement-based seismic design (DDBD) is widely popular due to the effectiveness of the design approach for achieving the structure’s predefined displacement limits. The seismic vulnerability assessment is computed on DDBD-designed structures to anticipate the future state of the structure, which has the potential to enhance the current design. In the present study, 4, 8, and 15-storey reinforced concrete (RC) frame structures are designed using DDBD and force-based design (FBD) under soft, medium, and hard soil conditions. A displacement profile is generated considering life safety (LS) and collapse prevention (CP) performance limits identified as per FEMA 356 (2000). The design response spectra to calculate base shear are taken from the revised IS 1893 Part-1 (2016) at zone-V. The nonlinear multi-mode pushover analysis is performed to investigate RC frame buildings and evaluate RC frames’ nonlinear behavior in terms of drift profiles and seismic vulnerability by generating fragility curves. The R factor determined by nonlinear static analysis varies between buildings based on their height, soil conditions, and performance status but is observed to be more than the code-specified number. The estimated level of damage to RC frame structures built on soft soil sites is moderate or between 1.5 and 2.5. Nonetheless, the likelihood of collapse for all studied frames is less than the threshold collapse of 10%.