Multiscale Modeling and Seismic Fragility Analysis of Corroded Precast Concrete Frame

Precast concrete frames have been widely used, though little is known about their fragility under the combined influence of seismic excitation and corrosion. In this study, one four-story precast concrete frame with different corrosion levels is taken as an example, which is simulated by using a multiscale finite-element model consisting of solid elements for corroded beam-column joints and beam elements for beams and columns, respectively. A fiber model is proposed to simulate the hysteretic behavior of corroded steel bars by employing the user-defined material subroutine in Abaqus. The proposed multiscale finite-element model is validated through existing experiments, so that a balance between accuracy and computational costs is obtained. Based on the proposed finite-element model, the influence of corrosion on seismic fragility of the frames is investigated through incremental dynamic analysis. Four limit states regarding the maximum interstory drift ratio are defined to evaluate seismic fragility. The analysis results show that structural responses are highly random under different ground motions and corrosion levels. Meanwhile, the seismic fragility of the frame is significantly influenced by corrosion ratios, and the probabilities of exceedance show exponential growth with the increase of corrosion level for all four limit states.