The Structural Seismic Resilience And Consistent Collapse Probability Of Reinforced Concrete Frame

In the actual earthquake disaster, the collapse of structures due to the lack of seismic resistance is the main reason of causing a large number of casualties and economic losses. For the structures that are damaged but not collapsed in the earthquake, the most effective method to reduce the economic loss is to take the optimal restoration measures and schemes on the basis of determining the residual seismic capacity of structures. Therefore, in seismic design, it is not only to ensure no occurrence of structure callopse, but also should determine how much the seismic capacity remains. This seismic design process has great reference value for resisting sequence-type earthquakes or the restoration after disasters. Achieved by controlling the attenuation law of structural seismic capacity, the differentiated performance design with different importance and function is another attempt to performance-based seismic design. Furthermore, the current seismic code mainly considered the "consistent earthquake risk" (the 50 years exceedance probability of design earthquake intensity is 10% for all fortification intensity). The macro assessment of seismic performance of the structure in service period can be realized by integrating the seismic uncertainty during the service time into the seismic assessment system. In view of the above thinking, this paper has done the following work:(1) On the basis of structural damage evolution law, the residual seismic capacity ratio, the curve of seismic capacity ratio, the global and local structural seismic resilience index are defined in this paper. Referring to seismic damage performance design, the performance level of structural seismic resilience is determined based on the importance and function of structures. And the control of the seismic resilience performance is achieved by the global and local index control principle. Fragility analysis is applied to propose the computation method and limit value of residual seismic capacity ratio of structures under rare earthquakes. By applying the assessment method to the 8-storey RC frame, the feasibility of the structural seismic resilience index is proved. And comparing with the performance index of maximum story drift that is recommended in seismic code, the rationality of the seismic resilience assessment method is verified.(2)Taking the structural seismic resilience index (R) and the collapse margin ratio (CMR) as examples, the concept of relative and absolute seismic capacity of the structure is described, and the qualitative relationship between R and CMR is proved. This paper established the framework of seismic design based on structural resilience, whose performance indexes are global and local seismic resilience indexes, and put forward the ideas and method to improve the seismic resilience of structures. Two different reinforcement methods are applied to the original frame. The results show that the structural seismic resilience indexes of the isolated structure and the structure with viscous dampers can be improved by 13.02% and 10.66% respectively, and the improvement effect is mainly reflected in the DS2?DS4 damage states.(3) Referring to the research of many scholars, this paper suggested that earthquake intensity of 50-year exeedance probability 0.5% as extra earthquak. And the collapse probability limit of the first class buildings under extra earthquake is determined as 1%, by raising the fortification standard of one degree. According to the new code for collapse resistance of structures, it is proposed that the uniform collapse probability limit value are 50-year collapse probability 0.03%,0.1% and 0.5% to the ABC fortification building respectively. And taking the limit as the basis, the earthquake intensity of each fortification is modified. Combining the idea of "uniform collapse" and "seismic resilience", the structural residual seismic capacity ratio during service period is introduced, which provides the macro assessment of seismic performance duiring the structure design worklife. The cases study of frame and two reinforced frame show that the 3 frames both meet the uniform collapse probability limit. And the structural seismic resilience grade is higher, the 50-year collapse probability of structures is low, the 50-year residual seismic capacity ratio is closer to 1.