DEVELOPMENT OF FRAGILITY CURVES FOR PRECAST CONCRETE FRAMES COMPARING THE METHODS OF STATIC PUSHOVER AND INCREMENTAL DYNAMIC ANALYSIS

Fragility curves provide damage probability as a function of ground motion characteristics and design parameters. In this study, we developed fragility curves for the precast reinforced concrete system, used in the construction of buildings in some high earthquake-prone zones in Iran. For accurate seismic demand estimation, we developed a numerical model for the precast beam-to-column connection based on the experimental results presented in the relative research. Incremental Dynamic Analysis (IDA) of the 3 and 5-story frames was conducted under the appropriate ground motion records set. The records database includes 10 far-fault records and10 near-fault records in which 5 records have pulses and 5 records do not have pulses. In IDA, multiple nonlinear dynamic analyses of the frames were performed using the OpenSees software under the ground motion records, each record scaled to several levels of seismic intensity from 0.1g up to the level at which structural collapse occurred. Based on the IDA results, the median and standard deviation values for the construction of the fragility curves were proposed at the four damage states of slight, moderate, extensive and complete. Results demonstrate that for a given seismic intensity level, the precast frames are more seismic vulnerable than the cast-in-place moment resisting frames. At a given level of seismic intensity, seismic vulnerability at four damage sates increases with increasing the height of the frames. The probability of exceeding the complete damage state at the design earthquake level was obtained to be 0.56 and 0.63 for the 3 and 5-story precast concrete frames, respectively.Considering that incremental dynamic analysis requires large computation efforts, we evaluated the possibility of using the static pushover analysis (SPO) in the development of fragility curves. For this purpose, the fragility curves were derived based on the pushover curves using the SPO2IDA algorithm. The results show that for all considered models at four damage states, the SPO method provides an acceptable approximation of the fragility curves. The accuracy of the SPO method in the development of fragility curves is improved at higher levels of response. The fragility curve of the 3 and 5-story frames for the complete damage state, developed based on the SPO method, is about 8 percent more than the corresponding curve obtained from the IDA method. Generally, for all structural models and all damage states the probability of exceedance obtained from the SPO method is about 12 percent more than that obtained from the IDA method.