Seismic Collapse Safety Margin And Direct Earthquake Loss Of Reinforced Concrete Structures

With the development of social economy and the progress of science and technology,the economic losses and social consequences caused by strong earthquake are becoming more and more serious.This makes the earthquake loss evaluation a hot research topic in the earthquake engineering.A reasonable earthquake loss estimation is very significant for reducing building seismic risk and guaranteeing normal operation of building functions.Earthquake loss estimation,at present,covers the direct losses,e.g.property loss due to building damages/collapse and casualties,and indirect losses such as that generated in downtime after an earthquake shock.Existing researches put their main efforts on property loss due to building damages or collapse.And such loss has relatively a more direct relationship with structural characteristics.Thus,a much more accurate earthquake loss estimation will be accomplished if the correlation between earthquake loss and seismic safety performance(structural collapse safety margin)could be directly established.With this motivation,on the basis of previous researches,studies about the influences of structural collapse safety margin on earthquake loss,listed as follows:(1)In order to investigate the effect of structural collapse safety margin on reducing earthquake losses,a structural earthquake loss estimation method incorporating collapse safety margin ratio(CMR)is proposed.The probabilistic characteristics of structural damages,i.e.from light damage to collapse,and the variation rule of associated earthquake losses,are analyzed by CMR curves.Then,the studing is validated by the reinforced concrete structures.(2)The relationship between collapse margin ratio and the occurrence probability of different damage levels at given ground motion intensity is established by vulnerability analysis.A discussion is implemented systematically pertaining to the influence of structural seismic collapse resistance on the damage state and direct earthquake loss of structure with different CMR.(3)On the basis of the above-mentioned research of the relationship between CMR and earthquake loss at given ground motion intensity,the variability of expected annual earthquake loss(EAL)vs.CMR is studied by incorporating seismic hazard.The statistic relationships between EAL and CMR,EAL and probability of MCE,EAL and uncertainty are established.The advantage and disadvantage factors influencing annual earthquake losses are analyzed.(4)Annual collapse probability is obtained through the combination of collapse vulnerability analysis with seismic hazard analysis under the framework of total probability theory.Further,the relation between annual collapse probability and CMR is established.Then acceptable CMRs are determined based on the lower limit of annual collapse probability which comes from collapse probability corresponding to rare earthquakes.With the design acceleration response spectrum specified in Chinese seismic design code,a so-called CMR spectrum is developed that can provide reference for collapse resistance design(5)A new assessment method of structural seismic collapse resistance is proposed based on acceptable collapse safety margin ratio.The research on the correlation of CMR and earthquake loss is effectively used to estimate earthquake insurance premium rate.And it will be a new idea to develop earthquake insurance premium rate model.