近断层地震动下减隔震连续梁桥向量型强度指标选取

Selection of vector-valued intensity measures for seismic isolated continuous girder bridges subjected to near-fault ground motions

强度指标是描述地震动特性及对结构反应影响的重要指标,在性能抗震设计框架下则构成了联系地震动水准和结构反应的量化参数。目前对具有速度脉冲特性的近断层地动的强度指标的研究仍有限。本文以某减隔震连续梁桥作为研究对象,基于OpenSees有限元软件建立三维分析模型,通过输入40条典型近断层地震动,得出算例需求参数DM(支座滞回能、桥墩滞回能、总输入能、墩顶漂移率、支座位移和主梁位移),然后通过线性回归分析对常见的23种强度指标和需求参数进行相关性分析,以可决系数R^(2)大小作为标准,建议Housner谱烈度(HI)可作为单一近断层地震动强度指标的最优选择。进而考虑向量型强度指标,以方差膨胀系数VIF作为标准,以解决参数间的多重共线性;随后,分别以峰值速度(PGV)和HI作为主变量,进行两组多元线性回归。结果表明,HI和峰值位移(PGD)适用于减隔震连续梁桥抗震性能评估,且较好表征近断层地震动的最优向量型强度指标。

Ground motion intensity measure is an important measure to describe the characteristics of ground motion and its influence on structural response.Under the framework of performance-based seismic design,it constitutes a quantitative measure connecting ground motion level and structural response.At present,the research on the intensity measure of near-fault ground motion with velocity pulse characteristics is still limited.In this paper,a seismic isolation continuous beam bridge is taken as the research object.Based on the OpenSees finite element software,a three-dimensional analysis model is established.By inputting 40 typical near-fault ground motions,the demand measures(DM)of the example are obtained(bearing hysteretic energy,pier hysteretic energy,total input energy,pier top drift rate,bearing displacement and girder displacement).Then,the correlation analysis of 23 common intensity measure and demand measure is carried out by linear regression analysis.Taking the size of the coefficient of determination(R^(2))as the standard,it is recommended that Housner intensity(HI)can be used as the optimal choice for the intensity measure of a single nearfault ground motion.Then considering the vector intensity measure,the variance inflation factor(VIF)is used as the standard to solve the multicollinearity between measures.Subsequently,the peak ground velocity(PGV)and HI are used as the main variables for two groups of multiple linear regression.The results show that HI and peak ground displacement(PGD)are the optimal vector-valued intensity measures suitable for seismic performance evaluation of isolated continuous girder bridges and can better characterize near-fault ground motions.