Probabilistic seismic assessment of RC frame structures in North of Iran using fragility curves

In this article, the fragility curves of RC structures with 3, 5 and 8 stories in Iran have been studied. The structures which have been estimated in this article have the system of RC Intermediate Moment Frame which is designed in accordance with Standard No. 2800 (Third Edition). These models in order to make a non-linear analysis in 3D form, they were modeled in OpenSEES software. The structure analysis was selected of the type of increasing dynamic analysis. In selecting the records of the earthquakes, it was tried that the characteristics of the selected records to be close to the conditions of the construction as much as possible. For this reason, the far-from the fault records of the FEMA P695 Code was used. The selected records were scaled from 0.1g to 1.5g with 0.1g steps and in each step, the structure was analyzed. The IDA curves were drawn for three types of structures under consideration up to structural complete damage. Then using MATLAB software and considering the lognormal probability distribution, the failure probability for each performance level was calculated and the fragility curves for Max Inter Story Drift in different levels of PGA were drawn. The results indicate that in comparing the structure behavior with different heights, it can be said that with the increase of height, the structure reaches to non-linear zone sooner and the structure capacity decreases. In general, with the structure height increase, the structure vulnerability in four specified levels of damage (slight, moderate, extensive and complete) increases but the trend of the increase of damage probability decreases. For the low rise RC structures (Intermediate moment-resisting frame) which have been built in accordance with the Standard No. 2800 (Third Edition), the Probability of extensive and complete damage in earthquakes with PGA’s less than 0.4g and 1.0g accordingly is almost insignificant. For the mid and high rise buildings, the probability of extensive and complete damages in earthquakes with PGA’s less than 0.3g and 0.7g is almost insignificant.