Study On Multi-parameter Seismic Fragility Analysis Of Steel Reinforced Concrete Transfer High-rise Structure

To meet the multifunctional requirements of high-rise buildings, more and more transfer structures are adopted in high-rise buildings, and become one developing trend of high-rise buildings. However, deformation concentration and energy accumulation at transfer storey more likely occur in transfer structures, and damage may easily be induced by earthquake excitations. To improve the poor seismic behaviors of transfer structures, based on the full consideration of earthquake three factors and the seismic intensity parameter sensitivity analysis, the seismic fragility surface was presented to evaluate the SRC transfer frame structural seismic vulnerability, which is the double parameter evaluation method. The influence on transfer-story stiffness ratio and height to the vulnerability assessment result of SRC transfer frame structure were discussed. The main works and conclusions are as follow:(1) Based on steel reinforced concrete transfer frame structural dynamic time history analysis of the sensitivity analysis about20seismic intensity parameter, the four performance of correlation, efficiency, practicality and proficiency were evaluated, and the seismic intensity parameters had greater influence on structural seismic demand were selected. Analysis results show that the spectrum acceleration of the first cycle SA1, the peak ground motion velocity PGV and the magnitude M had the greater influence on SRC transfer frame structural seismic demand. It was suitable for the evaluation parameters used to the structural seismic fragility analysis.(2) The regression analysis of dynamic time history analysis results of SRC transfer frame was carried out. The seismic fragility surfaces and the equations of all damage states were established. The seismic reliability of SRC transfer frame was evaluated and the probability of exceedance of all damage states between the fragility surface and fragility curve were compared. The results show that the probability of exceedance of fragility surfaces considered more intensity parameter(magnitude or epicentral distance) was greatly different from fragility curves. The vulnerability assessment method only with one parameter has obvious limitation, and the fragility analysis method of multi-parameter was more comprehensive and reasonable to the SRC transfer structure. (3) The change regularity of the vulnerability assessment difference between fragility surfaces and curves was analyzed with ground motion intensity. The results show that with the increase of the ground motion intensity, the difference of exceedance probability between fragility surfaces and curves was decreased in the basic condition. The difference of exceedance probability was increased in the moderate and severe damage states. But the change regularity of exceedance probability between fragility surfaces and curves was not significant in slight damage state.(4) The changes in the inter-story drift ratio and the vulnerability assessment results of SRC transfer frame with the transfer-story stiffness ratio were analyzed. The results show that with the increase of the transfer-story stiffness ratio, the transfer maximum inter-story drift ratio of SRC frame structure was decreased and the transfer-story displacement mutations was effectively decreased. Under the rare ground motion of7degrees, with the increase of the transfer-story stiffness ratio, the probability of exceedance of the SRC transfer frame in basic condition and slight damage state can be increased gradually. The difference of exceedance probability of SRC transfer frame in moderate and severe damage states was little.(5) The changes in the inter-story drift ratio and the vulnerability assessment results of SRC transfer frame with the transfer-story height were analyzed. The results show that with the improvement of the transfer-story height, the maximum inter-story drift ratio of SRC frame structure transfer upper story was decreased and the maximum inter-story drift ratio of SRC frame structure transfer lower story was increased. The transfer-story displacement mutations was more and more obvious. Under the rare ground motion of7degrees, with the increase of the transfer-story height, the probability of exceedance of the SRC transfer frame can be decreased gradually in basic condition, and can be increased gradually in slight damage state. The difference of exceedance probability of SRC transfer frame in moderate and severe damage states was little.