Fragility Analysis Of Reinforced Concrete Frame-shear Wall Structures Under Main Shock-aftershock Sequences

After a strong earthquake,damaged structures has not been repaired in time,the aftershocks often pose a greater threat to the building and personnel safety.This paper takes the frame-shear wall structures as the research object to carry out the multivariate probabilistic demand analysis and fragility analysis under the actions of mainshock-aftershock sequences by the cloud-method and the improved strip-method.The collapse resistance of the structures under mainshock-aftershock sequences is evaluated quantitatively by the strip-truncated IDA method.The main research contents are as follows:(1)The frame-shear wall structures consist of two parts with different deformation characteristics.The deformation curves are generally bending and shearing type.Selecting the interstory drift ratio as the engineering demand parameter cannot well reflect the damage states of the structure.In this paper,the applicability of different engineering demand parameters to the frame-shear wall structures is studied.The correlation between seismic intensity measures and earthquake demand parameters in probabilistic demand analysis is compared by the cloud-method.(2)The resistance of structures to aftershocks under different levels of mainshocks is investigated by an improved strip-method.The probabilistic seismic demand model at different levels of mainshocks still approximately satisfies logarithmic linear relationship.When the difference of section angles between interlayer shear walls is selected as the seismic demand parameter,it shows a good regularity.The multivariate linear regression analysis is used to establish the conditional multivariate aftershock probabilistic demand model of the structure.(3)The multivariate probabilistic seismic demand model considering the structure of the mainshock-aftershocks is established by the binary quadratic polynomial.The mainshock-aftershock influence coefficient is used to quantify the amplification phenomenon of the seismic responses of the main aftershocks.(4)The conditional aftershock fragility analysis of the structure under different levels of mainshocks is applied to quantitatively evaluate the resistance on aftershock of the structure damaged by mainshocks.The formula of total probability theorem(TPT)is used to derive the fragility function considering the mainshock-aftershocks.The collapse fragility analysis is carried out by the strip-truncated IDA method.The collapse resistance of the structure under the mainshocks and mainshock-aftershock sequences is quantitatively compared.It is mainly reflected in the small difference between the mainshocks and the aftershocks,and this effect increases first,and then decreases with the increase of the earthquake intensity.As the mainshock level increases,the anti-aftershock capability of the structure decreases continuously.Compared with the single mainshock,the logarithmic standard deviation in the structural fragility curve increases significantly after the main aftershocks,while the structural response is more discrete.