Performance-based earthquake analysis of 2-span bridgesystem using BridgePBEE
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摘要: 桥梁结构的振动特性受场地条件及土—结相互作用影响显著,为提高桥梁结构的抗震性能,减少因结构破坏而产生的经济损失,进一步开展考虑场地土体非线性以及土—结相互作用对桥梁结构地震反应影响的研究工作十分必要。本文以一典型桥梁结构为例,着重介绍了美国太平洋地震工程研究中心基于性能的桥梁有限元模拟平台BridgePBEE应用中所涉及的地震动选取、桥梁结构建模、土体本构选择以及基于构件的桩—土—桥梁结构体系损伤评估方法,为研究震后桥梁结构经济损失分析方法提供可行性方案。Abstract: This study aims to introduce a graphical user interface (BridgePBEE) to assess the seismic performance of coupled soil-structure systems under the Performance-Based Earthquake Engineering (PBEE) framework. A three-dimensional (3D) Finite-Element (FE) model for a typical simple bridge configuration is developed using BridgePBEE to conduct time history analysis of the bridge-ground system. The nonlinear dynamic response of the bridge during multiple suites of earthquake excitations is studied. Seismic loss in terms of repair cost for pre-defined performance groups is derived thereafter. This study shows that the local site soil profile affects the seismic response of the bridge considerably and should be considered in design procedures.
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图 1 1989年洛马普列塔地震中桩顶与承台连接处剪切破坏[10]
图 2 1999年集集地震中乌溪桥桥墩剪切破坏[11]
图 3 BridgePBEE桩—土—桥梁结构体系有限元动力分析模型[19]
表 1 地震动基本参数
分组 地震记录 时间 台站 MW vs30 断层距
R/kmPGA/g 纵向 横向 竖向 LMLR Borrego/A-ELC 1968 El Centro Array 9 6.8 213.44 45.66 0.127 0.057 0.030 LMSR Lomap/CAP 1989 Capitola 6.9 288.62 15.23 0.511 0.395 0.446 Near Impvall/H-ECC 1979 EC County Center FF 6.5 192.05 7.31 0.211 0.234 0.223 SMLR NorthR/SCS 1994 Sylmar-Converter Sta East 6.7 251.24 5.35 0.612 0.865 0.550 SMSR Impvall/H-CAL 1979 Calexico Fire Station 6.5 231.23 10.45 0.128 0.078 0.055 其中:LMLR:大震MW=6.5—7.2,断层距R=30—60 km;LMSR:大震MW=6.5—7.2,断层距R=15—30 km;Near:MW=5.8—7.2,近断层R=0—15 km;
SMLR:小震MW=5.8—6.5,断层距R=30—60 km;
SMSR:小震MW=5.8—6.5,断层距R=15—30 km表 2 桥面板的截面特性
参数 取值 弹性模量/MPa 23 580.900 剪切模量/MPa 9 825.375 单位重量/kN•m-3 23.55 截面面积/m2 6.029 4 横轴惯性矩/m4 3.075 7 竖轴惯性矩/m4 63.101 扭转常数/m4 8.645 表 3 钢筋混凝土桥墩截面属性
参数 取值 纵筋直径(US #) 11 纵筋数 44 纵筋率/% 1.9 箍筋直径(US #) 8 箍筋率/% 0.84 箍筋间距/m 0.152 4 钢筋单位重量/kN•m-3 76.97 钢筋屈服强度/kPa 455 054 混凝土单位重量/kN•m-3 23.56 混凝土无侧限强度/kPa 27 580 表 4 混凝土(Concrete 02)材料属性
混凝土材料参数 核心混凝土 覆盖层混凝土 弹性模量/MPa 26 582 26 582 抗压强度/kPa –38 298 –27 579 峰值压应变 –0.00 289 –0.002 破坏强度/kPa –35 921 0 极限压应变 –0.020 73 –0.006 卸载斜率比率 0.1 0.1 抗拉强度/kPa 5 362 3 861 拉伸软化刚度/kPa 1 860 764 1 930 531 表 5 钢筋(Steel 02)材料属性
钢筋材料属性 取值 初始刚度/MPa 20 000 屈服强度/MPa 455 钢筋硬化率 0.01 表 6 场地土层本构模型参数
PIMY 土层1 土层2 土层3 深度范围/m 0—6.7 6.7—13.4 13.4—43.9 密度/ton•m-3 1.3 1.5 1.8 剪切波速/m•s-1 软弱土场地vse=191 m/s 120 250 300 中软土场地vse=207 m/s 180 180 300 中硬土场地vse=305 m/s 250 300 400 粘聚力c/kPa 软弱土场地vse=191 m/s 30 30 75 中软土场地vse=207 m/s 25 60 75 中硬土场地vse=305 m/s 60 75 80 表 7 各类场地条件下土—桩—桥结构体系前3阶振型频率
振型阶次 软弱土vse=191 m/s 中软土vse=207 m/s 中硬土vse=305 m/s 刚性基础 1 1.349 74 1.469 64 1.543 21 1.643 84 2 1.771 93 1.749 85 2.165 72 2.442 72 3 1.776 28 1.752 04 2.320 2 2.592 44 -
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