【作者】 张玉芬；

【导师】 赵均海；

【作者基本信息】 长安大学 ， 结构工程， 2010， 博士

【摘要】 钢管混凝土经过多年的发展,在传统钢管混凝土的基础上,已经出现了多种新的结构形式。由于钢管混凝土在高层建筑、大跨桥梁等结构工程中广泛的应用,柱承受的荷载越来越大,因此出现了内置型钢、内置钢管或多管以及CFRP筒增强的新型钢管混凝土重载柱,本文统称之为复式钢管混凝土结构。该结构在有效减小构件截面面积的同时,又可明显提高承载能力和抗火能力,而且具有更好的延性。近几年的理论研究和工程实践表明,应用复式钢管混凝土是切实可行的,并且有很大的发展潜力。本文以复式钢管混凝土作为研究对象,为方便分析和便于设计应用,将复式钢管混凝土分为内圆钢管、型钢、CFRP增强型钢管混凝土及复式空心钢管混凝土四种形式。对各种截面的复式钢管混凝土的轴压性能进行理论分析和数值计算,拟建立统一可行的刚度和承载力计算方法。另一方面,节点是钢管混凝土体系中非常重要而又薄弱的环节。而我国大多数建筑的楼盖采用钢筋混凝土梁板结构,推广应用钢管混凝土柱的关键之一是解决钢管混凝土柱与钢筋混凝土梁的连接。因此本文设计了一种新型复式钢管混凝土柱与钢筋混凝土梁的连接形式——外钢管不连通环梁节点,由于楼层间外钢管不连通,梁纵筋可在节点区内贯通,传力路径明确,节点整体性强,施工简便,具有良好的应用前景。本文主要研究工作有：1.抗压刚度和承载力是结构构件重要的力学性质。本文基于简单叠加、钢管混凝土统一理论和弹性力学的方法对复式钢管混凝土轴压刚度进行了研究；分析了混凝土横向变形系数、钢管泊松比和含钢率是影响组合柱轴压刚度的主要因素。2.本文提出了组合约束效应系数,把钢管混凝土统一理论研究成果推广应用于复式钢管混凝土轴压强度计算中,所得到的承载力计算公式形式统一,计算简便；同时,运用双剪统一强度理论分析各种工况下复式钢管混凝土组成部分的极限承载能力,根据极限平衡原理得出组合柱的轴压承载力。以上两种方法均取得了较好的结果,并对复式钢管混凝土承载力的影响因素进行了分析。3.根据轴压性能研究,分析复式钢管混凝土的性能影响参数,并对各类型的复式钢管混凝土进行参数优化设计,得出最优的复式钢管混凝土设计理念。通过对各种截面复式钢管混凝土在受力性能和经济性上的对比,以及出于对其梁柱连接形式的考虑,认为内圆外方双钢管混凝土是比较理想的复式钢管混凝土结构,在实际工程中具有广阔的应用前景。4.对四个复式钢管混凝土外钢管不连通环梁节点试件进行低周反复荷载试验,分析研究该类型节点在恒定轴力和反复剪力作用下的抗震性能,对结构的破坏形态、破坏机制、滞回曲线、骨架曲线、位移延性、刚度退化、耗能能力等性能进行了较为深入系统的研究。建立了该新型外钢管不连通环梁节点的恢复力模型,可以较好地反映其滞回性能,可作为结构弹塑性地震反应分析时参考。5.采用有限元软件ANSYS对复式钢管混凝土节点进行三维非线性有限元模拟,得到了节点单调加载的荷载-位移曲线,并与试验的骨架曲线进行比较。同时对该节点的轴压性能进行研究,分析节点的内部受力机理,讨论了混凝土强度,内钢管尺寸及环梁配筋对节点轴压受力性能的影响。结合试验研究和有限元结果对该新型节点承载力验算、设计方法和构造措施提出一些建议。更多还原

【Abstract】 Concrete Filled Steel Tube (CFST) has already experienced several structural forms from the traditional ones after many years of development. As CFST has been used widely in high-rise buildings, long-span bridges etc, the columns are required to increases not only high bearing capacity but also good ductility. Therefore, one new CFST column reinforced by circular steel tube or steel column or CFRP cylinder, has arisen as heavy-loaded columns which is called composite CFST structure in this thesis. This structure can effectively reduce members’ cross-section area, and also significantly improve the load capacity, anti-fire capabilities with better ductility. In recent years, the composite CFST structure has been verified its feasibility in theoretical research and engineering practice, showing a great potential for more development.To facilitate the analysis and design applications, the composite CFST was classified as four forms, i.e. inner-steel-tube-enhanced CFST, steel-column-enhanced CFST, CFRP-enhanced CFST and hollow composite CFST. For various sections of the composite CFST, this paper established a unified calculation method of the compressive stiffness and bearing capacity by theoretical analysis and numerical calculation. On the other hand, the connection is the very important and weak part in CFST system. While the reinforced concrete beam-slab structure is applied in the majority of Chinese buildings. Therefore, to solve the problem of connection between CFST and RC beams is one of the keys to apply CFST structure. This paper put forward one new connection——Ring Beam Joint with Discontinuous Outer Tube between composite CFST and RC beams. The outer tube is discontinuous in joint zone, longitudinal reinforcement of RC beam can be run through to ensure loads transferred in the joint core zone, and the construction can preserve the structural integrity, so this new joint has a good application prospects.The mayor contributions of the work presented in this thesis are listed as follows:1. Compressive stiffness and bearing capacity are the important mechanical properties of structural elements. Based on simple superposition, unified theory of CFST and method of elasticity, axial compression stiffness of composite CFST has been studied. The main factors such as coefficient of lateral deformation of concrete, Poisson’s ratio of steel and steel ratio, evidently influenced the axial compression stiffness of the composite column.2. This paper presented the composite confinement factor in order to apply unified theory of CFST into the strength calculation of composite CFST, and the formula can be easily used for all the sections included. Meanwhile, every component of the composite CFST under the ultimate state was analyzed by the Twin Shear Unified Strength Theory. Then according to principle of superposition, the compressive bearing capacity of the composite columns can be calculated by the method of limit equilibrium. The both methods have achieved good agreement with the experimental results, and the influencing factors to the axial bearing capacity were also analyzed.3. Optimal design was obtained for every type composite CFST columns by Parameter Optimization according to the axial behaviors analysis. With consideration of the connection with RC beams, the section of circle inside and square outside was considered as more ideal one among the various sections of composite CFST columns by comparison of mechanical properties and steel ratio among all the sections of composite CFST. This optimal composite CFST structure can be widely applied in practice engineering.4. In order to study the seismic behavior of this new connection system, the thesis carries out the experiment of 4 specimens under the cyclic loading. Failure modes, damage mechanism, hysteresis curve, skeleton curve, displacement ductility, stiffness degradation and energy dissipation capability of the joint under fixed axial force and repeated shear force were analyzed in detail. The restoring force model of the Ring Beam Joint with Discontinuous Outer Tube was established with consideration of the better hysteretic behavior, which can be available of the elastic-plastic seismic response analysis as references.5. A three-dimensional nonlinear finite element analysis was performed to simulate the joint behavior by software ANSYS. The obtained load-displacement curve of monotonic loading simulation was compared with the skeleton curve of experimental results. At the same time the axial properties was studied in order to analyze the joint’s internal mechanism. The axial behaviors were discussed under the influence of the strength of concrete, inner steel tube and reinforcement of ring beam. Coming from the results of experiment and finite element method, some suggestions were put forward for checking the bearing capacity, and some design method and construction measures were also given for the new joint.更多还原