新型带肋中空薄壁方钢管混凝土的静力和滞回性能研究

Due to saving more steel and its simple joint, the square concrete-filled stiffened thin-walled steel tubular columns received extensive attention from academy and engineering. However, researches indicate that the square concrete-filled stiffened thin-walled steel tubular columns have many disadvantages such as bad ductility, big weight and bad fire resistance. An effective method, which can be used to improve the ductility and fire resistance, reduce the total weight of the structure and the number of welding seams, is to weld cold-formed thin-walled angle steels to be the outer steel tube and set the inner steel tube at the hollow section. This kind of specimens collectively called the hollow concrete-filled stiffened cold-formed thin-walled square steel tubular (HCFSCTSST) column. However, researches about the HCFSCTSST column have not yet been reported so far. Using experimental method and numerical simulation method, the calculating ways of the speciman under the static or dynamic load were investigated. Based on experimental study, numerical mechanism analysis and parameter analysis, the influence of inner steel tube on the ductility of the speciman is clarified and simplified calculation methods of the bearing capacity of the stub column and the beam-columns are presented. In addition, the effect of the dynamic load on the capacity of energy dissipation, stiffness and ductility of the beam-column is studied and the practical restoring force model is proposed. The above work can be used to supply scientific evidence for helping this innovative speciman to be applied to actual projects and relative criterion revision.

带肋薄壁方钢管混凝土柱由于用钢量少、节点简单等优点已受到学术界和工程界的广泛关注。但研究表明，带肋薄壁方钢管混凝土柱存在延性差、自重大和耐火性能较差等缺点。外钢管采用冷弯薄壁角钢焊接而成、在中空截面内置钢管被视为一种有效的方法,可提高该类构件的延性和耐火性能，同时还可有效的减小结构自重和焊缝数量。该类构件统称为"带肋中空冷弯薄壁方钢管混凝土柱"。但时至今日，尚未见和该类构件相关的研究报道。本项目拟采用试验方法和数值模拟法，对该类构件在单调和滞回荷载作用下的计算方法开展应用基础研究。基于试验研究、数值机理分析和参数分析，明晰内钢管对构件延性的影响规律；建立该类轴压、偏压构件承载力的简化计算方法；研究往复荷载作用对该类压弯构件的耗能能力、刚度和延性的影响规律；确定该类构件的实用恢复力模型。以上工作为该类新型构件在实际工程中的应用和相关规范的修订提供科学依据。

本项目研究了中空夹层薄壁钢管混凝土构件和复式薄壁钢管混凝土构件在单调加载下的力学性能。同时还进行了中空夹层薄壁钢管混凝土压弯构件的滞回性能研究。具体进行了以下几个方面的工作：.(1)分别以径厚比、径宽比、长细比、偏心距等为主要变化参数，较系统地进行了一系列轴压、纯弯和压弯试验。.(2)用ABAQUS有限元软件建模方法对轴压、纯弯和压弯构件进行受力全过程模拟，模拟结果和试验结果吻合较好。.(3)运用该模型对轴压、纯弯和压弯构件受力全过程中各部分的荷载-变形关系曲线、应力分布、钢管约束力和破坏模态进行机理分析。.(4)运用该有限元模型对构件的荷载-变形曲线和N-M相关曲线进行参数分析，主要包括如下参数：截面含钢率、径宽比、材料强度、长细比及偏心率。.(5)在以上机理分析和参数分析的基础上，提出了中空夹层薄壁钢管混凝土构件和复式薄壁钢管混凝土构件的轴压、纯弯和压弯构件承载力的实用计算方法。.(6)共对9根压弯构件进行滞回试验，其中包括6根薄壁中空夹层钢管混凝土构件和3根普通薄壁钢管混凝土构件。研究表明：试件破坏表现为钢管局部屈曲、混凝土压碎和钢管开裂；随着轴压比的增大，试件延性、耗能能力随着减小；中空夹层薄壁钢管混凝土构件的耗能能力明显高于普通薄壁钢管混凝土构件。.(7)利用ABAQUS有限元软件建模法对中空夹层薄壁钢管混凝土压弯构件进行数值模拟，模拟结果与试验结果较吻合。运用该模型对此类构件受力全过程进行机理分析。主要对各部分纵向应力及钢管与混凝土间的相互作用进行分析。钢管约束力主要集中在角部，因此角部混凝土强度有显著提高。.(8)运用该有限元模型对中空夹层薄壁钢管混凝土压弯构件滞回曲线的骨架线进行参数分析。研究发现：随着混凝土强度、钢管强度的增大，构件的承载力变大；随着长细比的增大，构件承载力减小；随着轴压比的增大，构件的延性显著降低。构件的承载力随着径厚比的增大而减小。.(9)最终在机理分析和参数分析基础上，提出了中空夹层薄壁钢管混凝土压弯构件的恢复力模型。