Probability-based Seismic Performance Study Of Multi-storey Reinforced Concrete Frame Structure

Along with the implementation of China’s new civil engineering norms, theperformance of the seismic capacity of the building structure, designed in accordance withthe new norms, become a concern of the engineering. Due to many uncertainties inengineering, using probabilistic methods to measure and assess structure seismicperformance is more reasonable and accurate.First this paper analyzes reliabilities of office and residence buildings’ beams andcolumns separately, the study shows that: either office or residential, the reliability indexof their beams and columns is decreasing with the earthquake load effect ratio (ρ_E)increasing; increasing with the live load effect ratio (ρ_q) increasing. With Certain loadeffect ratio (ρ_qandρ_E), the reliability index of the beams and columns of office is greaterthan residential. Either office or residential, the difference between the columns and beamsreliability index is higher under higher seismic level, namely “ability differential” bigger,so that “strong column and weak beam” design is more effective.Then according to China’s new 《Code for seismic design of buildings》（GB50011-2010）three RC frame structure models with various moment magnifyingcoefficients of columns were designed. In consideration of the randomness of structureparameters and the ground motion,20sample is established based on Latin hypercubesampling method, three structural models were analyzed based on randomly incrementaldynamic analysis, seismic peak acceleration (PGA) as the vibration intensity indicators,the vertex displacement angle (RDA) as the reaction parameters of the structure, to obtainthe IDA curves of the structures. The analysis shows that when the earthquake intensity islesser, the moment magnifying coefficient value basically has no effect on the seismicresponse of the structure, and the earthquake intensity is larger, the response of thestructure with a more moment magnifying coefficient value is smaller; On the basis of theIDA analysis, the seismic demand probability model of each structure is established, andfour seismic performance levels are defined, then random Pushover analysis for each structure is carried out, to determine the various performance level limit value. Finally,seismic fragility analysis is carried out for each structure to obtain fragility curves. Theresults show that the moment magnifying coefficient value has a certain impact on thefragility of the structure: the greater its value is, the smaller the collapse probability of thestructure under a specific earthquake motion is; within a certain range, the larger theplastic degree of the structure is, the more obvious the seismic performance of thestructure with a more moment magnifying coefficient value is improved.