Seismic Evaluation and Fragility Curves of a Typical School Building

Seismic Evaluation and Fragility Curves of a Typical School Building

At present, pushover analysis based on the capacity spectrum method is often used for the detailed seismic evaluation of existing typical school buildings in Taiwan. The performance-target ground acceleration is compared with the site’s peak ground acceleration(PGA) for a design earthquake with a 475-year return period in order to evaluate whether the seismic capacity is sufficient. However, as stated in FEMA 440, the results of the evaluation are too conservative for relatively short-period structures. In this report, incremental dynamic analysis(IDA) of a typical school building is used to study its seismic capacity and how conservative is the capacity spectrum method. Additionally, from the results of IDA, a seismic fragility curve of a sample school building can be built in order to evaluate the probability of collapse of this building under an earthquake with the evaluated performance-target PGA. From the analysis results, the roof displacement estimated by the capacity spectrum method is on average 2.25 times the value from nonlinear dynamic analysis for a typical three-story school building; under the performance-target earthquake for seismic evaluation, this structure has a 5.3% probability of collapse, which is acceptable, and the specified performance target is a reasonable and conservative choice.