Damage evaluation of column bases in steel moment-resisting frames based on fishbone model and Bayesian model updating

Abstract

This paper presents a method of evaluating seismic damage of column bases in steel moment-resisting frames based on fishbone model and hierarchical Bayesian updating method. In this study, a fishbone model considering the flexibility of column bases was presented instead of the traditional fishbone model with rigid column bases and shear building model with unobtainable stiffness of beam ends and column bases. The fishbone model could be used to update the rotational and shear stiffness of column bases, and also to update the stiffness of the beam ends. First, the eigenvalue problem of the fishbone model considering the flexibility of column bases was formulated. Then, the method of identifying the shear and rotational stiffness of column bases in steel frames was proposed based on the hierarchical Bayesian model updating algorithm using incomplete modal data. The seismic damage of column bases was evaluated by comparing the identified stiffness before and after earthquakes. The effectiveness of the proposed method was numerically investigated with a 5-story building model. The influences of the selection of parameters in algorithm, structural modal data and degrees of freedom on the identified results were studied. Finally, the applicability of the method to realistic damage evaluation of column bases was also examined by a serial of shaking table tests on a 3-story 2-bay large-scaled steel frame specimen.