董召先, 孙治国, 李宏男, 王东升, 司炳君. 液化场地钢筋混凝土桥墩残余位移分析[J]. 工程力学, 2023, 40(10): 154-168. DOI: 10.6052/j.issn.1000-4750.2022.01.0083
引用本文: 董召先, 孙治国, 李宏男, 王东升, 司炳君. 液化场地钢筋混凝土桥墩残余位移分析[J]. 工程力学, 2023, 40(10): 154-168. DOI: 10.6052/j.issn.1000-4750.2022.01.0083
DONG Zhao-xian, SUN Zhi-guo, LI Hong-nan, WANG Dong-sheng, SI Bing-jun. ANALYSIS ON RESIDUAL DISPLACEMENT OF REINFORCED CONCRETE BRIDGE PIERS STANDING IN LIQUEFIABLE FIELD[J]. Engineering Mechanics, 2023, 40(10): 154-168. DOI: 10.6052/j.issn.1000-4750.2022.01.0083
Citation: DONG Zhao-xian, SUN Zhi-guo, LI Hong-nan, WANG Dong-sheng, SI Bing-jun. ANALYSIS ON RESIDUAL DISPLACEMENT OF REINFORCED CONCRETE BRIDGE PIERS STANDING IN LIQUEFIABLE FIELD[J]. Engineering Mechanics, 2023, 40(10): 154-168. DOI: 10.6052/j.issn.1000-4750.2022.01.0083

液化场地钢筋混凝土桥墩残余位移分析

ANALYSIS ON RESIDUAL DISPLACEMENT OF REINFORCED CONCRETE BRIDGE PIERS STANDING IN LIQUEFIABLE FIELD

  • 摘要: 为探究场地液化对钢筋混凝土(Reinforced Concrete, RC)桥墩残余位移影响机理,首先基于OpenSees有限元计算平台阐述了液化场地-结构有限元数值建模方法,通过与离心机试验结果对比验证了建模方法的可靠性。其次以一座实际工程中的单桩单柱式桥墩为原型,发展了液化场地-RC桥墩建模方法,建立非液化场地-桩-RC桥墩数值模型(模型1)和液化场地-桩-RC桥墩数值模型(模型2),对两模型输入近断层地震动进行非线性动力时程分析。讨论了模型2场地液化情况,并对模型1与模型2的场地位移、桩身位移、桩身最大屈服曲率延性系数、墩顶残余位移及墩顶残余位移随地震动峰值加速度(PGA)变化情况进行对比。结果表明:地震过程中,模型2场地各深度出现不同程度液化现象;且土体中上部均达完全液化状态,土体水平极限抗力损失最大,对桩身侧向约束严重降低。液化导致场地震后残余位移显著增加,场地对桩身震后约束增强,导致桩顶残余位移增大。另外,由于地震过程中中上部液化土体对桩身侧向约束严重降低导致桩身塑性变形显著增大、桩身最大塑性变形位置明显下移以及桩身塑性变形区扩展,引起桩身更为严重的塑性损伤,进而增大桩顶残余位移。液化场地震后残余位移增大与地震过程中对桩身约束降低共同导致桩顶残余位移增加,经桥墩放大传递至墩顶,引起墩顶残余位移增大。液化场地墩顶残余位移随PGA增大速度明显大于非液化场地桥墩,主要原因可能是随PGA增加,场地液化程度加深。

     

    Abstract: To study the influence mechanism of site liquefaction on Reinforced Concrete (RC) pier residual displacement, the numerical simulation method of liquefied site-structure upon OpenSees finite element platform was described at first, and the reliability was verified by comparing with centrifuge test results. Then based on a practical extended pile-shaft, a liquefied site-RC pier simulation method was developed, the nonliquefied site-pile-RC pier numerical model (model 1) and liquefied site-pile-RC pier numerical model (model 2) were established, near-fault ground motions were inputted two models for dynamic time history analysis. Model 2 site liquefaction was discussed firstly, then site displacements, pile displacements, pile maximum curvature ductility coefficients, pier residual displacement and variation of pier residual displacement with peak ground acceleration (PGA) were compared between Model 1 and Model 2. The results show that liquefaction is different along depths in model 2 site during the earthquake. The upper-middle soil reaches a complete liquefaction state, soil loses most horizontal ultimate resistance, and pile lateral constraint is seriously reduced. Liquefaction results in a significant increment in liquefied site residual displacement post-earthquake, and pile top residual displacement may increase due to the enhanced post-earthquake constraints of pile body. The pile plastic deformation increases significantly, maximum plastic deformation position of pile downward obviously, and pile plastic deformation zone expands, which leads to more serious plastic damage to pile and further increases pile top residual displacement. The increase of residual displacement post-earthquake in liquefaction site and the reduction of pile constraint during the earthquake lead to an increment of pile top residual displacement, which is amplified by pier and transferred to pier top, causing increase of pier top residual displacement. The pier residual displacement in liquefied site is significantly faster than that in non-liquefied site with the increase of PGA, which may be due to the deepening of site liquefaction with the increase of PGA.

     

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