Seismic Fragility Assessment of RC Moment-Resisting Frames Designed According to the Current Chinese Seismic Design Code

Seismic fragility was assessed for 72 RC moment-resisting frame building structures designed according to the current Chinese seismic design code for buildings, taking into account the uncertainty of the structural material strength and earthquake ground motions. The site soil type, the number of stories, and the seismic protection intensity were considered to be the main design variables of the reference structures. Fragilities for four damage levels, i.e., fully operational, operational, repairable, and collapse prevention, are developed in this study. The global seismic damage index, which reflects the effects of individual structural components, and the maximum inter-story drift ratio, which is closely related to the seismic damage of structural and nonstructural components, was employed as the damage identifiers. For each frame structure, the probability of exceeding each damage level in an earthquake with a specified PGA was determined by conducting nonlinear time history analysis. Fragility curves for the four damage levels were derived by regression analysis using the nonlinear least-squares method. The structural reliability of RC frames against earthquakes was examined using the developed fragility curves. The results indicate that seismic performance objectives for RC frame structures designed in accordance with the current Chinese code can be achieved with good reliability.