西安地区风险导向地震动参数的确定

Determination of risk-targeted ground motion parameters in Xian region

摘要:

为实现一致倒塌风险,对风险导向地震动参数进行了研究．首先,基于ArcGIS Engine平台,采用离散算法对西安地区的计算控制点进行了概率地震危险性分析；然后,根据地震危险性分析得到的年超越概率曲线,考虑结构的地震易损性,基于地震动决策参数已有的研究成果,通过风险积分得到了各计算控制点的风险导向巨震、大震、中震的地震动参数PGA_RV、PGA_RM、PGA_RD,并计算了风险系数R_c（风险导向大震的地震动强度与大震对应地震动强度之比）以及风险导向巨震、风险导向大震与风险导向中震地震动参数的比例关系K₁、K₂；最后,分别取结构易损性对数标准差βR为0.5、0.6、0.7、0.8、0.9、1.0,通过参数影响分析研究了βR对PGA_RM、R_c、K₁和K₂的影响．研究结果表明:倒塌概率并不会随着极罕遇地震对应地震动强度的增加而增加；PGA_RM、R_c、K₁和K₂都随着βR的增加而增加；βR越大,对PGA_RM和R_c的影响越大,对K₁和K₂的影响不变；K₁和K₂比PGA_RM和R_c对βR敏感,K₁对βR最敏感．本文得到的西安地区的风险导向地震动参数可以为抗震设计提供参考．

Abstract:

To achieve consistent collapse risk, risk-targeted ground motion parameters were investigated. First, based on the ArcGIS Engine software, a discrete algorithm was used to analyze the probability of seismic hazard in Xian region. Then, by considering the seismic fragility of the structure, the risk-targeted ground motion parameters of very rare earthquake, maximum considered earthquake, and design basis earthquake for each control point were obtained by risk integral based on the annual exceeding probability curves obtained from seismic hazard analysis and the ground motion decision parameters obtained from existing research results. The risk-targeted ground motion parameters were denoted as PGA_RV, PGA_RM, and PGA_RD, respectively. The relation between the risk coefficient R_c (defined as the ratio of PGA_RM to the ground motion intensity corresponding to maximum considered earthquake) and K₁ (defined as the ratio of PGA_RV to PGA_RD) and K₂ (defined as the ratio of PGA_RM to PGA_RD) were calculated. Finally, based on the parameter effect analysis, the effect of βR (i.e., logarithmic standard deviation of structural fragility) on PGA_RM, R_c, K₁, and K₂ was investigated with its value chosen to be 0.5,0.6,0.7,0.8,0.9, and 1.0, respectively. Results show that the collapse probability did not increase with the increase of the ground motion intensity corresponding to very rare earthquake. Parameters PGA_RM, R_c, K₁, and K₂ all increased with the increase of βR. The larger βR was, the greater the effect on PGA_RM and R_c was, while the effect on K₁ and K₂ remained unchanged with increasing βR. Compared with PGA_RM and R_c, K₁ and K₂ were more sensitive to βR, and K₁ was the most sensitive to βR among all the parameters. The risk-targeted ground motion parameters obtained in Xian region can provide references for seismic design.