汶川地区震后钢筋混凝土框架结构的地震易损性研究

Seismic Vulnerability of Post-earthquake Reinforced Concrete Frame Structures in the Wenchuan Area

以汶川地震为研究背景,针对震后典型钢筋混凝土框架结构进行地震易损性研究。基于Cornell理论框架结合汶川地质资料,拟合出考虑场地特点的地震危险性模型,同时定义损伤水平状态及限值指标,以概率解析易损性研究方法为基础,运用考虑地震动参数的解析易损性评估方法绘制汶川地区钢筋混凝土框架建筑的地震易损性曲线。研究结果表明:考虑地震动参数的概率解析易损性研究方法是一种有效的地震易损性评估方法;以PGA作为地震强度输入指标的结构反应,随自振周期的增大体系最大响应的相关性降低,结构各个损伤状态的失效概率均随之增大。

The purpose of this study was to analyze the seismic vulnerability of the post-earthquake reinforced concrete frame structure in Wenchuan,China.High earthquake intensities and large areas that are affected increase grievous personal and economic losses.Based on disaster investigations,reinforced concrete frame structures accounted for the high proportion of buildings destroyed.Researchers at Cornell University in the United States proposed a probabilistic method that considers the influence of different seismic intensities in the same area.From a quantitative standpoint,this method can evaluate the seismic hazard level of the target area within a given time period using ground motion parameters and probability analysis to facilitate the engineering seismic design process.A simplified method for assessing vulnerability based on ground motion parameters was proposed,and vulnerability curves for the reinforced concrete frame structure in Wenchuan were drawn to describe the probability of the various levels of damage.The curve between the ground motion parameters and the annual probability based on the Cornell University theory is accurate,reasonable,and somewhat conservative.This study used the finite element software OpenSEES to conduct nonlinear static and dynamic history analyses.The OpenSEES software is widely used because of advantages in its fiber model division,higher computing speed,and better accuracy.Approximately 300 samples of the structure were established using the OpenSEES software in order to perform the nonlinearstatic analysis.During the analysis,the yield displacement and the maximum story drift were chosen as a measure of the level of seismic capacity in the structure.The two-fold energy equivalent yield displacement method proposed by FEMA273 was also used to determine the yield displacement of structures and maximum story drift.Research methods that consider the probability of earthquake ground motion parameters by combining Latin hypercube sampling,nonlinear static analysis,dynamic time history analysis,and statistical regression analysis are effective for the assessment of seismic vulnerability.The relationship between the ground motion parameters and failure probability curve can intuitively represent the seismic performance of the structure.Because the method is based on probabilistic seismic demand and aseismic capacity,the prospect is good for its application in seismic vulnerability analysis.The level of damage table and corresponding inter-story displacement angle limit table contained in this paper reflect the characteristics of the building structures and seismic features in earthquake disaster area.The table was based on Wenchuan earthquake survey data and structural seismic codes in China.Combined with the results of the HAZUS risk assessment,it represents an effective standard for evaluation.We also concluded that the proposed method for vulnerability assessment based on ground motion parameters is feasible.With the inputting parameter of the PGA,the correlation of the maximum response of the structure decreases with increases in the natural period and the corresponding probability of structural failure is enhanced.