Earthquake Vulnerability Analysis Of RC Frame Structures Above Ground Considering SSI Effect

With the gradual application of a new generation of seismic design methods based on performance in engineering,seismic vulnerability analysis at different levels of behavior has become an important means of seismic safety assessment of building structures.Since the existing seismic design codes in China have not yet considered the effect of soil-structure dynamic interaction（ie,SSI effect）on the seismic performance of building structures,a numerical analysis of seismic vulnerability of building structures under SSI effect was carried out to accurately evaluate building structures Earthquake safety has important reference value.In this paper,Open Sees is used to establish a numerical analysis model of soil-reinforced concrete（RC）frame structure,and the method of finite element modeling is verified in the aspects of frame structure member level,structure level and ground motion input of finite element model,and A typical soft soil site with a layer thickness of 80 meters and an 8-layer RC frame structure are taken as an example.Six engineering demand parameters（EDP）and 22 ground motion intensity indicators（IM）of the frame structure are analyzed by incremental dynamic analysis method（IDA）The effectiveness evaluation was carried out,and the influence law of considering or not considering SSI effect on the selection of seismic intensity index was compared;on this basis,the seismic vulnerability curve of RC frame structure considering SSI effect was proposed.The study reached the following conclusions:1)From the effectiveness evaluation of EDP,the SSI effect makes the most effective engineering demand parameter change from the maximum displacement Dispx to the maximum acceleration Accx.In order to facilitate the results that are not disturbed by EDP selection,this paper selects the maximum interlayer displacement angleθ_maxas the engineering demand parameter.2)According to the effectiveness evaluation of IM:no matter what kind of IM index,the SSI effect increases the dispersion of the IDA curve;among the common peak IM indicators,the peak ground speed PGV and PGD are more sensitive to the SSI effect Compared with PGA and energy-based IM indicators I_A,they are more sluggish;however,the sensitivity of spectral parameters such as S_a,S_v,S_d,PS_a,and PS_vto the SSI effect is very consistent.In this paper,the HI（Housner intensity）index,which is sensitive to the SSI effect and is the most effective,is used as the ground motion intensity index.3)Based on the assessment of seismic vulnerability withθ_maxand HI（Housner intensity）,the following conclusions are drawn through the vulnerability analysis of the eight-story RC frame structure with or without considering the SSI effect:Compared with the fixed The basic model,the complete finite element model that considers the SSI effect reduces the seismic demand of the structure significantly at all performance levels;the consideration of the SSI effect at different performance levels reduces the percentage of seismic demand that is different,at the NO（normal use）level The SSI effect reduced the seismic demand by 49.61%;the SI（immediate use）level reduced the seismic demand by 54.85%;the LF（life safety）level was reduced by as much as 79.71%;compared to other performance levels,the The consideration of the SSI effect at the CP（prevention of collapse）level has the smallest reduction in seismic demand.That is,except for the collapse,the higher the performance level,the greater the reduction in the seismic demand of the structure.