热激励环向驱动嵌入式形状记忆合金丝主动约束混凝土墩柱的加固机理及设计理论研究

The main failure type of piers is mostly caused by the shear failure in the plastic hinge region due to the insufficiency of the ductility and the shear resistance. How to improve the seismic resistivity of the piers is an emergency problem for researchers at home and abroad. This project proposes to embed spiral shape memory alloy (SMA) wires into the cover of the concrete in the plastic hinge region and to thermally prestress the wires to apply active confinement to piers. The advantages of such method could lie in that it solves the problems existing in current active confinement methods, including the protection issue, durability and aesthetics since the exposure of the retrofitting materials and anchorages. This research combines theoretical analysis, numerical simulation and experimental tests to achieve following goals. Firstly, the controlling method of the effective prestressing force within SMA wires and the mechanism of stress transfer are explored. Then the evaluation criteria and physical model of stress transfer are developed. Secondly, the constitutive model of the SMA confined concrete, the numerical model between mechanical parameters and material properties of confined piers and the crack-control model are developed to investigate the retrofitting mechanism of SMA confined concrete piers. Thirdly, the loading capacity and seismic resistivity of confined piers are studied, and the damage-evolution model is developed. Finally, the design theory and retrofitting technique of actively confined concrete piers using thermally prestressed spiral SMA wires are formed to facilitate the application of such new retrofitting method in civil engineering.

延性和抗剪能力不足造成塑性铰区的剪切破坏是桥墩最主要的破坏方式，如何对其进行抗震加固是国内外亟待解决的问题。本项目提出将形状记忆合金（SMA）丝环向嵌入塑性铰区混凝土保护层中，通过热激励驱动SMA丝产生预应力的主动约束加固方法，解决既有主动约束加固技术由于加固材料及锚具外露、需要张拉机具而存在的成品保护困难、耐久性和美观性差等难题。通过理论分析、数值模拟和试验研究结合，首先研究SMA丝有效预应力的控制方法和应力传递机理，建立其评价指标及应力传递物理模型；然后建立SMA丝约束混凝土本构模型，揭示加固墩柱的宏观力学参数与材料性能参数之间的力学计算规律，构建裂缝控制模型，明确SMA丝约束混凝土墩柱的加固机理；再研究加固后墩柱的承载能力和抗震性能，建立其损伤演化模型；最后形成基于性能的热激励环向驱动嵌入式SMA丝主动约束加固混凝土墩柱的设计理论及加固技术，促进此新型加固方法在国内外的工程应用。

延性和抗剪能力不足造成塑性铰区的剪切破坏是桥墩最主要的破坏方式，如何对其进行抗震加固是国内外亟待解决的问题。针对既有主动约束加固技术由于加固材料及锚具外露、需要张拉机具而存在的成品保护困难、耐久性和美观性差等难题，本项目提出将形状记忆合金（SMA）丝环向嵌入塑性铰区混凝土保护层中，通过热激励驱动SMA丝产生预应力的主动约束加固方法。首先，通过SMA丝的力学试验结合理论分析和数值模拟，研究了SMA丝有效预应力的控制方法和应力传递机理；然后，通过试验和数值模拟相互验证，建立了SMA丝约束混凝土本构模型，揭示了加固墩柱的宏观力学参数与材料性能参数之间的力学计算规律，明确了SMA丝约束混凝土墩柱的加固机理；最后，通过拟静力试验和数值模拟相互验证，研究了加固后墩柱的承载能力和抗震性能。本项目研究成果为促进此新型加固方法在国内外的工程应用提供了理论与技术支撑。