A Study on Seismic Capacity Assessment and Retrofit of Hospitals(III)
Under the policy moved by Construction and Planning Agency, Ministry of the Interior and the Ministry of Education, the task of seismic capacity assessment of public and school buildings has been conducted nationwide in full scale. Based on experiences gained in reviewing the seismic capacity assessment projects, the applicant finds that the engineers are treating all the structures as moment-resisting frames, and not taking into account, in their analysis, the effect of short-columns caused by window stages. As a result, the analyses are not reflecting the actual behavior of the structures, and may in turn overestimate the seismic capacity. The design target of “strong-column-weak-beam” emphasized in seismic structural design is conceptually correct but impractical for RC structures, since the beams are too stiff to form plastic hinges as their stiffness are substantially enhanced by the concrete floor so that the reinforcing steel bars are not yielding at negligible flexural deformation, even under strong earthquakes. The ductility of the overall structures is much less than expected as a consequence. Furthermore, most of the school buildings were found to be damaged in shear failure of the columns along the corridors. This is due to the “short-column” effect caused by the partially infill brick walls of the window stages. The seismic assessment is not reliable if the actual behavior of the structures is not reflected in the analysis. This project is to propose a seismic assessment procedure for RC structures based on pushover analysis using ETABS by considering the design details of the structural members and infill walls. Typical hospital structures will be considered as the objective in this study. The analytical models are to be considered as shear buildings to reflect the actual structural behavior of “weak-column-strong-beam”, and the infill walls are to be simulated with equivalent bracings. For structures identified as seismically vulnerable, this project is to propose effective retrofit schemes with least impact on the daily operations of hospitals. The task is to develop two types of energy-dissipative braces respectively with buckled strut and high-strength aluminum alloy inside. The mechanical behavior and optimal design parameters of the proposed devices will be realized via component tests, while the feasibility of using the proposed devices for seismic retrofit of structures will be verified via seismic performance tests by shaking table.
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