Seismic response trends evaluation and finite element model calibration of an instrumented RC building considering soil-structure interaction and non-structural components

摘要

This paper presents experimental system identification and numerical modelling of a three story RC building monitored for a period of more than two years. System identification was conducted for 50 earthquake response records to obtain the frequencies and damping ratios considering the flexible base model that take into account soil-structure interaction (SSI). Trends of variation of modal parameters were investigated by correlating the peak response acceleration at the roof level with identified frequencies and damping ratios. A general trend of decreasing frequencies with increasing level of response was observed and quantified, whereas for damping ratios no clear trends were discernible. In the second part of the study, a series of three dimensional finite element models (FEMs) of the building were developed to investigate the influence of various structural and non-structural components (NSCs), such as cladding and partitions, as well as soil underneath the foundation and around the building, on the building dynamics. The aforementioned components were added to the FEM one by one and corresponding natural frequencies computed. The final, all-inclusive FEM was then calibrated using a sensitivity based model updating technique and experimental modal parameters by tuning the stiffness of structural concrete, soil and cladding. The updated FEM was further validated by comparing the recorded acceleration time histories to those simulated using the FEM. Finally, the updated FEM was used in time history analyses to assess the building serviceability limit state seismic performance. It was concluded from the investigations that natural frequencies depend quite strongly on the response magnitude even for low to moderate level of shaking. NSCs and SSI have been demonstrated, through both numerical models and FEM updating, to have a significant influence on the seismic response of the building. A calibrated FEM proved to be less conservative for simulating seismic responses compared to the initial FEM but the building still performed satisfactorily.