椭圆形FRP-混凝土-钢双壁空心管柱力学性能及设计方法研究

A novel type of elliptical FRP-concrete-steel double-skin tubular columns (EDSTCs) was proposed in the proposal for the research objects of high-rise bridge piers under severe corrosive environment. The proposed EDSTCs possess many advantages, such as excellent corrosion resistance, big flexural rigidity around major axis of symmetry as well as excellent seismic behavior. Experimental study, theoretical analysis and numerical simulation of the proposed EDSTCs for mechanical behavior and design method were conducted. Firstly, monotonic axial compression performances of stub EDSTCs were studied, the interaction mechanism among elliptical FRP tube, elliptical steel tube and the core concrete was revealed, the stress-strain model of confined concrete in EDSTCs under axial compression was proposed and practical bearing capacity formula for stub EDSTCs under axial compression was present. Secondly, cyclic axial compression performances of stub EDSTCs were studied, and the stress-strain model of confined concrete in EDSTCs under cyclic axial compression was proposed. Thirdly, eccentric compression performances of stub EDSTCs were studied, the stress-strain model of confined concrete in EDSTCs under eccentric loading was proposed and practical bearing capacity formula for stub EDSTCs under eccentric loading was present. Fourthly, axial and eccentric compression performances of long EDSTCs were studied, and the bearing capacity formulas of long EDSTCs under axial and eccentric loading were proposed, respectively. Fifthly, seismic behaviors of EDSTCs were investigated, and practical bearing capacity formula for EDSTCs was obtained. A set of mechanical performance analysis, testing and design methods for EDSTCs was built through the above researches.

以处于恶劣腐蚀环境下的桥梁高墩等为研究对象，本项目提出一种耐腐蚀、抗弯刚度大（绕强轴方向）和抗震性能优越的新型构件——椭圆形FRP-混凝土-钢双壁空心管柱，并对其力学性能和设计方法进行系统深入的试验研究、理论分析和数值模拟。首先，研究短柱的单调轴压力学性能，明晰椭圆形FRP管、钢管与核心混凝土之间的相互作用机理，提出单调轴压下椭圆形非均匀约束混凝土的应力-应变关系，建立轴压承载力公式；第二，研究短柱的循环轴压力学性能，提出循环轴压下椭圆形非均匀约束混凝土的应力-应变关系；第三，研究短柱的偏压力学性能，提出偏压下非均匀约束混凝土的应力-应变关系，建立偏压承载力公式；第四，研究长柱的轴压和偏压力学性能，分别提出长柱的轴压和偏压承载力公式；第五，研究空心管柱的抗震性能，提出实用的抗震设计方法。通过上述研究，建立一套实用的椭圆形双壁空心管柱的受力性能分析、试验与设计方法，为其工程应用提供科学依据。

对于处于恶劣腐蚀环境下的桥梁高墩等研究对象，为克服传统构件形式（如矩形钢筋混凝土空心柱、矩形中空夹层钢管混凝土柱等）的缺点，本项目提出了一种耐腐蚀、抗弯刚度大（绕强轴方向）和抗震性能优越的新型构件——椭圆形FRP-混凝土-钢双壁空心管柱，并对其力学性能和相关设计方法进行了系统深入的试验研究、理论分析和数值模拟。本项目的主要研究内容及结论如下：. (1)椭圆形双壁空心管短柱的单调轴压力学性能：通过短柱的单调轴压试验研究和理论分析，明晰了单调轴压下椭圆形FRP外管、钢内管与核心混凝土之间的相互作用机理，提出了面向设计的单调轴压下组合短柱中约束混凝土应力-应变关系模型，建立了短柱的单调轴压承载力计算公式，所提模型和计算公式与试验结果吻合较好。. (2)椭圆形双壁空心管短柱的循环轴压力学性能：对短柱进行了循环轴压试验研究和理论分析，研究结果表明：截面比对加卸载曲线的塑性应变和应力退化的影响较小，提出了具有较高精度的循环轴压下椭圆形双壁空心管短柱中约束混凝土的应力-应变关系模型。. (3)椭圆形双壁空心管短柱的偏压力学性能：通过短柱的偏压试验研究、理论分析和数值模拟，明晰了偏压下椭圆形FRP外管、钢内管与核心混凝土之间的相互作用机理，提出了面向设计的偏压下组合短柱中约束混凝土的应力-应变关系模型，建立了具有较高精度的短柱偏压承载力计算公式。. (4)椭圆形双壁空心管中长柱的轴压和偏压力学性能：基于OpenSees的精细化有限元模拟方法，分析了多个关键参数对中长柱稳定系数的影响规律，分别建立了中长柱的轴压和偏压稳定承载力计算公式。. (5)椭圆形双壁空心管柱的抗震性能：通过组合柱的抗震性能试验研究和精细化有限元模拟，考察了截面比、FRP管厚度以及侧向力加载方式等参数对其抗震性能的影响规律，建立了椭圆形双壁空心管柱的侧向荷载-位移恢复力模型。. 上述研究建立了一套实用的椭圆形双壁空心管柱受力性能试验、分析与设计方法，为其工程应用提供了科学依据。