钢管混凝土柱的非线性剪扭复合效应研究

Concrete filled steel tube column is a kind of steel-concrete composite column with excellent mechanical property, which has been widely used in city viaducts, girder bridges in expressway and high-speed railway. From survey results of earthquake disaster recently, the compression-bending-shear-torsion complicate non-linear mechanical state always exists in piers with small ratio of shear span to height, leading to more serious damage, and the earthquake emergency rescue will be greatly affected. However, little literatures can be available about the influences of non-linear combined shear and torsion effect on the mechanical behavior of structural members, and the relevant theory and design method need to be proposed. Therefore, the quasi-static test on concrete filled steel tube columns subjected to combined compression-bending-shear-torsion load will be carried out, and the failure modes and seismic behavior of concrete filled steel tube columns under complex mechanical state can be obtained. Then the fiber beam-column model considering non-linear shear and torsion combined effect on the section will be proposed based on test results and theoretical derivation. The seismic analysis and evaluation on steel-concrete composite girder bridge structures with complex layout will be carried out using the dynamic time-history analysis method, and the key design factors will be also proposed. The non-linear mechanism and theoretical model of concrete filled steel tube columns will be comprehensively studied in this project.

钢管混凝土柱是在钢管内填充混凝土所形成的钢-混凝土组合构件，由于其力学性能优越，在我国城市立交桥、高架桥和高速公路、铁路高架桥中的应用日益增多。在地震作用下，空间布置复杂的梁式桥中剪跨比较小的墩柱由于处于压-弯-剪-扭非线性复合受力状态，其震害严重且修复困难，严重影响震后救援工作。目前关于非线性剪切和扭转复合效应对钢管混凝土柱力学性能的影响研究较少，相关分析理论和设计方法尚需完善。针对上述问题，本项目拟开展钢管混凝土柱在轴力-弯矩-剪力-扭矩复合受荷状态下的拟静力试验，研究其破坏机制和滞回特性，并结合试验结果和理论推导，建立可同时考虑非线性剪切和非线性扭转效应的钢管混凝土非线性杆系模型，然后采用开发的模型对空间布置复杂的钢-混凝土组合结构梁式桥体系进行抗震分析和初步评价。本项目研究成果将有助于完善钢管混凝土的非线性受力机理研究和分析模型。

为研究钢管混凝土柱在弯剪扭复合受力作用下的力学性能和破坏模式，本文进行了以下工作：.①开展了10个钢管混凝土柱在纯扭、弯剪和弯剪扭荷载作用下的拟静力往复加载及单调加载试验，得到了钢管混凝土柱在纯扭往复荷载及单调荷载作用下的荷载-变形曲线和钢管应变分布规律，钢管混凝土柱在弯剪及弯剪扭单调加载时的荷载-变形曲线和钢管应变分布规律，以及钢管混凝土柱在纯扭、弯剪和弯剪扭荷载作用下的破坏模式。试验结果表明，钢管混凝土柱在弯剪扭荷载下具有良好的承载能力和塑性性能，破坏模式取决于弯扭比和剪跨比，在弯剪及弯剪扭复合受力下，截面的轴向变形基本满足“平截面假定”，钢管混凝土柱在往复纯扭荷载作用下的骨架曲线与单调纯扭加载曲线基本重合。.②采用通用有限元程序ABAQUS进行了钢管混凝土柱的精细有限元建模及计算分析。在建模过程中重点探讨了材料的本构关系模型，然后将限元计算得到的荷载-变形曲线与试验得到的荷载-变形曲线进行比较，验证了有限元模型的准确性，为后面参数分析提供依据。.③通过进行大量有限元参数分析，考虑钢材屈服强度、混凝土强度、截面尺寸等因素对钢管混凝土柱的抗扭、抗弯、抗剪承载力的影响规律，得到了钢管混凝土柱的在纯扭、纯弯、纯剪荷载作用下的荷载-位移曲线和应力应变分布规律，并通过回归分析得到钢管混凝土柱的纯扭、纯弯、纯剪承载力和刚度的简化计算公式。在钢管混凝土柱抗扭承载力计算中考虑了钢管混凝土柱的长径比对抗扭承载力的影响。.④在大量有限元计算结果的基础上，研究了钢管混凝土柱在弯剪扭复合受力下的承载力相关关系，得到了考虑剪跨比影响的钢管混凝土柱的弯剪扭承载力相关方程。