近断层脉冲地震动下桥梁排架墩基于保险丝的损伤控制研究
Seismic Damage Control of Bridge Bents Retrofitted with Structural Fuse Under Near-fault Pulse-type Ground Motions
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摘要: 为增强临近断层区域桥梁双柱式排架墩的横向抗震性能,基于结构保险丝理念,引入防屈曲支撑(Buckling-Restrained Brace,BRB)作为牺牲性保险丝进行抗震性能提升.针对近断层脉冲型地震动的特点,采用单一函数解析模型模拟一组以矩震级、断层距为主要参数的低频脉冲分量,并叠加强震动记录滤波后的高频分量作为研究输入地震动.以一座公路桥梁中的典型排架墩为原型,建立动力分析模型,通过非线性地震反应时程分析,系统研究了BRB布置形式(人字、单斜和肘节式)、矩震级、断层距和脉冲数对排架墩损伤控制效果及抗震性能的影响.结果表明,采用BRB作为保险丝可明显提升排架墩的抗震性能,显著降低其地震损伤;位移放大型肘节式BRB体系较传统单斜式和人字形的耗能能力更强,在小位移情况下尤为显著.Abstract: Buckling restrained braces(BRBs)retrofitted to a double-column bridge bents as sacrificial components could enhance the lateral seismic performance of bridge near the fault area,based on the structural fuse concept.A single-function analytical model was used to simulate a group of low-frequency pulse components with moment magnitude and fault distance as the main parameters,according to the characteristics of near-fault pulse-type ground motions.The high-frequency components of strong motion record were obtained by time-frequency filtering and the low-frequency pulse components were superimposed to generate the input ground motion.The bents of an ordinary highway bridge were used as a reference for a dynamic analysis model and the effects of the BRB layout scheme(inverted-V,diagonal and toggle type),moment magnitude,fault distance,and the number of velocity pulses on the seismic performance of the bents were studied using a nonlinear time history analysis.The results show that installing BRBs can improve the seismic performance of bridge bents and reduce seismic damage.Furthermore,the energy dissipation capacity of toggle BRB systems is stronger than that of traditional inverted-V and diagonal BRB systems,particularly under small displacements.