基于截面纤维模型的UHPC-NC组合桥墩抗震性能研究

Study on Seismic Behavior of UHPC-NC Hybrid-piers Based on Fiber Element Model

针对传统钢筋混凝土桥墩在塑性铰区域损伤容限、耗能能力和变形性能的不足,提出将超高性能混凝土(UHPC)替代塑性铰区域普通混凝土(NC),并搭配高强钢筋,形成一种新型的UHPC-NC组合桥墩。为探讨这种组合桥墩的抗震性能,基于截面纤维模型编制了考虑轴力二阶效应的压弯构件非线性分析程序,通过与UHPC和NC桥墩低周往复荷载试验数据进行对比,验证分析程序的可靠性。在此基础上运用编制的程序分析轴压比、纵筋直径、纵筋强度和UHPC高度等参数对组合桥墩抗震性能的影响。结果表明:组合桥墩位移延性系数随着轴压比的增加而降低,随纵筋直径和纵筋强度的增大表现出先增大后降低的趋势,随UHPC替换高度的增加表现出先增大后逐渐平缓的特征,合适的UHPC替换高度是实现组合桥墩位移延性和经济性的重要前提。

In view of the limited damage tolerance, energy dissipation and deformability of the plastic hinge zone of traditional reinforced concrete piers, an innovative hybrid pier made of ultra high performance concrete(UHPC), normal concrete(NC) and high strength rebar was proposed. To discuss the seismic performance of this hybrid-pier, based on the fiber element model, a nonlinear analysis program was compiled for compressive and flexural members taking into account the second-order effect s of axial force. Based on the contrast analysis between cyclic loading test results of UHPC and NC pier samples under the invariable axial force and the calculation results, the precision of the program was proved. The factors affecting the seismic behavior of hybrid pier under different axial compression ratio, longitudinal bar diameters, longitudinal bar strength and UHPC height were analyzed. The results indicate that the displacement ductility coefficient of hybrid pier decreases with the increase of the axial compression ratio, increases first and then decreases with the increase of the longitudinal bar diameter and longitudinal bar strength, and increases with the increase of UHPC replacement height, but the curve gradually becomes horizontal when the replacing height amounts to a certain value, indicating that an appropriate replacing height on UHPC can balance the displacement ductility and economy.