Seismic Fragility Analysis And Comparison Of Reinforced Concrete Frame Structures With Different Algorithms

With the rapid development of social economy,people have gradually improved the demand for the building structures in comfort,and the investment is also increased.It's an important issue for researchers that how to reduce the losses of the building structures under the influence of the earthquake.Along with the development of performance-based seismic design philosophy,structural seismic fragility analysis came into being,and has become a common method for assessing structural losses.The uncertainty of the ground motion has a significant effect on the structural fragility analysis results.As an important part of the uncertainty of ground motion,the influence that the uncertainty of the ground motion parameters have on the fragility analysis needs further study.A simplified structural model which is intercepted from the structure is usually established to simulate the response of the structure under ground motions in traditional fragility analysis process.The difference between the results of the whole frame under bidirectional ground motions and the simplified model is also an urgent problem to be solved in the study.Based on these,this paper focuses on the influence of different ground motion parameters on the models that are established according to part of the structure and the whole frame,and compares the results of the fragility analysis.The following is the main contents.(1)Based on the earthquake and station information,select,rescale,analyze the ground motion records,and compare the differences between the essential of earthquake motions.(2)According to interception units,a simplified reinforced concrete frame structure model is established to analyze the fragility of the model under the ground motions of each group.This paper also studies the correlation between the time-history analysis results with the ground motion parameters.It shows that the seismic response of the low-rise structure is in the largest dispersion and more sensitive to PGA.The larger dispersion makes the fragility curve gentle,resulting in a high probability when the intensity of the earthquake is weak and a slow growth when the intensity of the earthquake is strong.And at the same time,the low-level structure is affected by the amplitudes of individual ground motion records easily.Middle and high-rise frame structures have small dispersion in response and overall stability when the intensity of the earthquake is small.(3)The finite element model of the whole structure of reinforced concrete frame is established to analyze the structural fragility under each group of ground motions.And the results of fragility analysis obtained from the two methods are compared.The results show that when analyzing the whole structure,the structural response of the low-rise frame disperses widely under ground motions.The simplified model obtained by interception units significantly overestimates the seismic performance of the low-rise frame structures,especially the anti-collapse ability.When analyzed by the whole frame,the middle-layer frame structure is greatly influenced by different ground motions,and the interception unit method weakens the response differences caused by different ground motions,resulting in inaccurate results.For high-level frame structure,analyzed by the whole frame,its seismic capacity has fully performed.In general,the probability of exceedance for the whole model is less than or close to the interception unit method.When the seismic fragility of the high-rise frame is studied by simplified model,the seismic capacity of the actual structure is often underestimated.(4)From the perspective of engineering application,for regular reinforced concrete frame structures with almost equal lateral stiffness in two horizontal directions,the lower and the middle is suitable to use the whole model for the analysis,and the upper layer can choose interception unit method.