| At present, Standard seismic design method can be summarized as "three levels, two stages", preventing the structure from collapsing and protecting the users. However, with the development of social economy, the equipment and non-structural members are more important and valuable than the structure itself. Even if the structure does not collapse under the earthquake, the economic loss is unbearable to the country.Therefore, based on performance design method, predecessors come up with the structural seismic vulnerability analysis which evaluate the seismic performance comprehensively and calculate the probability of failure states under different earthquake intensity from the perspective of probabilistic. Currently,2D frame is used to be object of study during the seismic vulnerability analysis. Analysis result of it is used to guiding the seismic design and evaluating loss.In fact, the structure is special. Consequently, whether the evaluation for seismic performance of the structure is accurate or not can not be ensured.The five storey steel frame structure under 7 and 8 degree earthquake resistance based on the existing design standard has been considered as the research object. The fragility curves of different performance index for the spatial steel frame and the plane steel frame under 8 degree seismic condition are studied respectively. The necessity of the research on the vulnerability of the spatial steel frame is expounded. Accordingly, the seismic vulnerability of the spatial steel frame structures under 8 and 7 degrees earthquake resistance are studied respectively. The seismic safety of the design results based on existing standard is verified, and some valuable results are obtained. The main work and results of this paper are as follows:First of all, the development of the structural seismic concept is summarized and seismic design method of steel frame to control performance is introduced in detail. In addition, based on the practical engineering, the space steel frame under 7 degree earthquake resistance, the space steel frame and the plane steel frame under 8 degree earthquake resistance are established.Secondly, considering the randomness of earthquake action and the structure itself,100 samples for each of the three structures were generated by the Latin hypercube sampling technique. RDA, ISDA and ?d is choosed to be the probabilistic seismic demand parameter. The log linear regression analysis is performed to the 300 samples, getting the function relation between the seismic demand parameters and the seismic intensity parameters.What's more, probabilistic seismic capacity analysis must be done on these samples, through the static elastic plastic time history analysis, the pushover curve of the samples will be obtained and the yield displacement of the structure is calculated. Based on the different performance level of the structure defined by the specification and the failure process of the structure, the method of quantitative performance threshold value is proposed. the limit values of different each performance index are determined.Lastly, according to the results of probabilistic seismic demand analysis and probabilistic seismic capacity analysis, probabilistic seismic vulnerability analysis is performed. Theory based on traditional reliability analysis method is used to study the failure probability of the seismic demand beyond the seismic capacity. Use the vertex maximum displacement angle (RDA), the maximum interlayer displacement angle (ISDA) and the displacement ductility ratio (?d)as the performance index to draw seismic fragility curves. Conclusions which is based on the analysis are as follows:The seismic fragility curves of the plane steel frame structure under 8 degree earthquake resistance are compared with the fragility curves of spatial steel frame under 8 degree earthquake resistance, obtaining the influence of different research objects on the seismic behavior of the structure.The reason of the difference between two structures has been proposed. Furthermore, the vulnerability curves of performance index limit difined by different method are analyzed. Method for quantifying performance limits proposed by this paper will ensure that the damage state of each index is unified. Finally.compare and analysis the difference of the seismic fragility curves among these index, indicating that the ISDA is the most appropriate index of all. ISDA will be advised to be the design index to ensure the safety. According to the fragility curves of ISDA, failure probability of different states for the space steel frame under 7 degree earthquake resistance and the space steel frame under 8 degree earthquake resistance can be educed, indicating that the structures designed according to cord can keep safe under "small earthquake"and "medium earthquake".However, Under the major earthquake, the collapse probability is too high.Therefore, Seismic design method based on the performance should be applied in the design of the engineering structure with a high level of importance... |
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