椭圆形FRP-混凝土-钢组合空心柱的截面优化和抗震性能研究

Fiber-reinforced polymer (FRP) composites have been widely used in civil engineering due to their excellent corrosion resistance, high strength as well as other advantages. Owning to the graceful shape and aesthetical appeal, elliptical columns are emerging gradually and have gained widely acceptance and popularity in practice. This research project focuses on a novel form of elliptical columns incorporating with FRP: elliptical FRP-concrete-steel double-skin tubular columns (EDSTC), which consist of an elliptical outer tube made of FRP, an elliptical/rectangular inner tube made of steel, and an annular layer of concrete filled in between. The novel elliptical column possesses many advantages, such as: light self-weight, excellent corrosion-resistance and exceptional seismic behavior, different bending stiffness around two axes of symmetry, which has a promising potential to be used as hollow bridge piers. Based on relevant findings of previous research conducted by the applicants as well as existing studies by other researchers, this research project will firstly optimize the cross-section of EDSTC by investigating affecting parameters such as elliptical aspect ratio, the thickness of FRP tube and the shape of inner steel tube. Through a comprehensive study combining both experimental and numerical approaches, the stress-strain model of confined concrete in EDSTC will be obtained. The stress-strain model will then be incorporated into fiber-element model for numerical simulation of the seismic behavior of EDSTC subjected to combined cyclic lateral loading and axial compression. This research project will provide theoretical design methods and pave way for the practical application of this novel elliptical column.

纤维增强复合材料（FRP）因其耐腐蚀、高强等优点在土木工程领域得到了广泛应用。椭圆形截面的结构柱，以其优美灵动的建筑外形，受到越来越多的青睐。本项目研究一种新型的应用FRP的椭圆形柱：椭圆形FRP-混凝土-钢组合空心柱。该椭圆形空心柱由椭圆形截面的FRP外管、椭圆形或矩形截面的钢内管、以及两管之间的填充混凝土构成。该椭圆形空心柱具有自重轻，优越的耐腐蚀性能和抗震性能等优点，并具有绕两对称轴不同的抗弯刚度，特别适用于桥梁结构中的空心桥墩。本项目在申请人前期相关研究以及其他已有研究的基础上，将对该椭圆形空心柱的截面形式进行优化，深入研究椭圆截面的长轴/短轴比，FRP外管厚度，钢内管形状等对其性能的影响；采用有限元分析和试验相结合的方法，建立该柱内填混凝土的应力-应变关系模型；建立基于纤维梁单元的理论模型，并结合侧向往复荷载试验深入研究其抗震性能。本项目将为其在实际工程中的应用提供重要理论依据。

纤维增强复合材料（FRP）因其耐腐蚀、高强等优点在土木工程领域得到了广泛应用。本项目主要研究了一种新型的应用FRP的椭圆形柱：椭圆形FRP-混凝土-钢组合空心柱。该椭圆形空心柱由椭圆形FRP外管、椭圆形或矩形截面的钢内管、以及两管之间的填充混凝土构成。椭圆形组合空心柱具有自重轻，优越的耐腐蚀性能和抗震性能等优点，并具有绕两对称轴不同的抗弯刚度，特别适用于桥梁结构中的空心桥墩。本项目进行了椭圆形空心柱的轴压性能和抗震性能试验，研究了椭圆形截面的长轴/短轴比，内部钢管的形状，空心面积率及FRP管厚度对其性能的影响，并提出了椭圆形空心柱的轴压承载力公式和抗震性能模拟方法。研究表明，椭圆形空心柱的长轴/短轴比对约束混凝土的抗压强度和极限轴向应变影响不大；具有椭圆形内钢管的试件比具有矩形内钢管的试件具有更高的混凝土约束强度和极限轴向应变；抗震性能试验中，随着长轴/短轴比的增大，椭圆形空心柱的延性先增大后降低。作为对比，本项目同时研究了矩形FRP-混凝土-钢组合空心柱（即FRP外管为矩形）的轴压性能和抗震性能，研究参数包括矩形截面的长边/短边比，内部钢管的形状，空心面积率和FRP管厚度。研究表明，椭圆形空心柱的性能均优于矩形空心柱的性能。另外，本项目研究了纤维缠绕角对于FRP-混凝土-钢组合空心柱的轴压性能和FRP-混凝土-钢组合空心梁的受弯性能的影响。研究采用了±45°、±60°和±80°纤维缠绕角的FRP管。研究表明，对于FRP-混凝土-钢组合空心柱，±80°纤维缠绕角的试件抗压强度最高，而±45°纤维缠绕角的试件极限轴向应变最大；对于FRP-混凝土-钢组合空心梁，所有试件均表现出优越的延性，而具有±45°纤维缠绕角的试件具有最佳的抗弯承载力。通过本项目的研究，将推动该新型椭圆形FRP-混凝土-钢组合空心柱在实际工程中的应用，为我国大规模的城市和基础设施建设提供一种外形美观，施工方便，同时具有优越耐腐蚀性能和抗震性能的高性能受压构件。

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