得益于强度优势，高强钢在满足结构工程设计要求时可有效减小结构自重，在超高层建筑和大跨结构等工程领域逐步得到应用。高强薄壁钢管混凝土作为一种典型的高强钢-混凝土组合结构形式，具有承载力高、自重轻和延性好等优点，在结构工程领域具有良好的应用前景。目前，部分地区（如宁波地区）受限于加工设备和技术限制，采用折弯工艺加工成型的钢管弯角外圆弧半径R与钢材厚度t（弯角外径厚比R/t）比值低于规范《结构用冷弯空心型钢》（GB/T 6728-2017）的下限值。为研究折弯工艺对高强薄壁钢管混凝土构件力学性能的影响，本文通过试验和有限元模拟分析不同折弯工艺对钢材的材料性能和弯角区残余应力分布规律的影响，并对不同折弯工艺下高强薄壁钢管混凝土柱开展轴压和抗震力学性能研究。主要研究内容如下：1. 对90个Q460高强钢材试件进行单轴拉伸试验，考察不同折弯工艺、钢材厚度、厚度损失和取样部位对高强钢材轴拉力学性能的影响，研究各试件的破坏模态、应力-应变曲线以及钢材性能指标，基于试验结果提出折弯工艺下冷弯空心型钢弯角区高强钢材的强度计算公式；2. 对壁厚为3mm和6mm的高强薄壁钢管试件进行残余应力试验与有限元研究，采用“盲孔法”对高强薄壁钢管试件的弯角区进行残余应力测试，研究试件残余应力的分布规律，运用ABAQUS有限元软件模拟不同折弯工艺下高强钢材的加工全过程，基于试验与有限元结果分析不同折弯工艺对钢管弯角区残余应力分布的影响；3. 对8个高强薄壁方形钢管混凝土柱进行单调轴压试验，考察试验柱的荷载-位移曲线、承载力和变形能力，建立采用不同折弯工艺的高强薄壁方形钢管混凝土柱的有限元模型，分析残余应力、加工效应、厚度损失和弯角外径厚比R/t对轴压试件的影响，基于试验研究和有限元分析结果提出外圆弧半径R的工程设计建议值；4. 对4个高强薄壁方形钢管混凝土柱开展低周往复加载试验研究，获得试件的破坏形态和滞回曲线，分析试件的承载力、延性系数、滞回耗能、强度和刚度退化等力学性能指标，并结合应变数据分析折弯工艺对高强薄壁方形钢管混凝土柱抗震性能的影响。
Beneficial from steel strength, high strength steel can effectively reduce the structural weight when meeting the requirements of structure design, and it is gradually applied in super high-rise buildings and long span structures. As a typical high-strength steel-concrete composite structure, high-strength thin-wall concrete-filled steel tube possesses the advantages of high bearing capacity, light dead weight and good ductility, so it has a good application prospect in the field of structural engineering. At present, due to the limitation of processing equipment and technology in some areas (such as Ningbo), the ratio of corner outer arc radius (R) to the thickness (t) of cold-formed steel tube does not meet the requirements of the specification "Cold forming hollow sectional steel for general structure" (GB/T 6728-2017). To investigate the influence of press-baking on the mechanical properties of high-strength thin-walled concrete-filled steel tubular columns, tests and finite element methods are applied to study the influence of press-baking on material properties and residual stress distribution in the corner area are investigated. And the axial compression and seismic properties of high-strength thin-walled concrete-filled steel tubular columns applying different press-baking method are figured out. The main contents of this paper are as follows:1. The uniaxial tensile test of 90 Q460 high-strength steel specimens were tested. The influence of press-baking method, steel thickness, thickness loss and sampling position on the material properties of high-strength steel specimens were investigated. Based on the experimental results, the material strength calculation formula of cold-formed hollow steel tube corner formed by press-baking method was proposed.2. The residual stress test and finite element study were carried out on high-strength thin-walled steel pipe specimens with wall thickness of 3mm and 6mm. The residual stress of high-strength thin-walled steel tubular specimens were tested by “blind hole method”, and the distribution law of residual stress was studied. The different press-baking method were simulated by ABAQUS. Based on the experiment and finite element model, the influence of press-baking method on the residual stress distribution in the machining corner was analyzed.3. A monotone axial compression test was carried out on 8 high-strength thin-walled square concrete-filled steel tubular columns, and the load-displacement curve, bearing capacity and deformation capacity of the test columns were studied. High-strength thin-walled square concrete-filled steel tubular column finite element models formed by different press-baking method were established to investigate the effect of residual stress, machining effect, thickness loss and the ratio of corner outer arc diameter (R) to thickness (t) in the corner area on axial compression specimens. Base on the result of test and finite element model, the design suggestion of the limit of outer arc radius (R) applied in the investigated press-baking method was put forward.4. An experimental study with low-frequency cyclic loads was carried out on 4 high-strength thin-walled square concrete-filled steel tubular columns, and the failure forms and hysteretic and skeleton curves of the specimens were obtained. The bearing capacity, ductility coefficient, hysteretic energy dissipation, strength degradation and stiffness degradation of the specimens were analyzed. And the influence of press-baking method on the seismic performance was analyzed based on the strain data.
