曲线形不锈钢管混凝土桁架结构失效机理与失效控制研究

It is believed that there is great potential to apply curved concrete-filled stainless steel tubular (CFSST) truss formed by two or more curved CFSST components with stainless steel tubular braces in large-span spatial structures, such as roof structures, sports stadiums and exhibition centers, not only for excellent structural properties and corrosion resistance but also for aesthetic appeals. However, seldom research has been conducted on curved CFSST truss, and the existing codes, for example, AISC (2005), AISI (2007), GB50017-2003, do not specify the design method for curved CFSST truss, this limits application of curved CFSST truss. This program will develop a multi-scale nonlinear finite element analysis (FEA) model to simulate the behaviour of curved CFSST truss. Firstly, a stainless steel-concrete composite fiber beam macro model, which can divide the composite sections into fibers and the user-defined material constitutive model can be incorporated in subprogram UMAT provided by ABAQUS, will be established to perform chords of curved CFSST truss. Then, interaction between the stainless steel tube and the core concrete will be study in order to build microscopic model in joint of curved CFSST truss. At the end, methodology of connecting microscopic finite element model to macro model will be proposed.The multi-scale nonlinear finite element analysis model will be verified through a number of experiments. Based on the modified material constitutive model of the core concrete, the influence of variations in the initial curvature ratio, nominal slenderness ratio, load eccentricity, distance of adjacent webs on the load capacity and failure modes of curved CFFST truss, characteristics of load versus deformation curve, nonlinear influence of locally deteriorating on structural response, stress and strain distribution, contact stress and internal force transfer mechanism, will understood by means of the multi-scale FEA model.Based on the parametric analysis, the limit state equations of curved CFFST truss will be proposed, which may be referred for practical engineering design.

曲线形不锈钢管混凝土桁架结构对于大跨度、大空间、建筑美观要求高的公共建筑具有良好的适用性，但目前对该类结构工作性能的研究尚少见报道，也没有系统的设计方法，制约了其推广应用。本研究拟根据纤维模型理论，建立曲线形不锈钢管混凝土弦杆纤维梁宏观模型，确定不锈钢管与核心混凝土的界面接触，寻找有限元微观模型与宏观模型的连接方法，构建曲线形不锈钢管混凝土桁架结构一致多尺度非线性有限元模型，并进行试验研究，验证模型的正确性。在明确不锈钢和混凝土材料本构的基础上，基于多尺度非线性有限元法，考察初始弯曲度、名义长细比等参数对曲线形不锈钢管混凝土桁架结构承载力和失效模式的影响规律，分析结构荷载-变形全过程关系曲线的特征，阐明局部损伤演化、应力应变分布、不锈钢管与混凝土相互作用以及杆件传力机制等受力机理，提出曲线形不锈钢管混凝土桁架结构失效极限状态方程。本研究可为曲线形不锈钢管混凝土桁架结构的应用和设计提供参考。

曲线形不锈钢管混凝土桁架结构对于大跨度、大空间、建筑美观要求高的公共建筑具有良好的适用性，本项目对曲线形不锈钢管混凝土单杆及桁架结构进行了较为系统的研究。.在曲线形不锈钢管混凝土单杆研究方面，进行了弯曲力学性能试验研究与分析，得到了初始弯曲度对该类构件的受弯力学性能的影响规律，并比较了曲线形不锈钢管混凝土受弯构件与直不锈钢管混凝土受弯构件、曲线形空不锈钢管受弯构件的受力特性、破坏模态及刚度与承载力异同。基于弹性理论推导了初始弯曲度对曲线形不锈钢管混凝土受弯构件弹性抗弯刚度和抗弯承载力的影响，而后通过参数分析回归修正了初始弯曲度对曲线形不锈钢管混凝土构件抗弯承载力和抗弯刚度的影响系数，提出了该类构件抗弯承载力和抗弯刚度的实用计算方法。.在曲线形不锈钢管混凝土不锈钢混凝土桁架结构研究方面，进行了双肢曲线形不锈钢管混凝土桁架受弯力学性能试验研究与分析，并与直不锈钢管混凝土桁架、曲线形空不锈钢管桁架进行了对比。得到了初始弯曲度、弦杆是否填充混凝土、腹杆布置形式等参数对该类桁架结构受弯力学性能的影响规律。建立了曲线形不锈钢管混凝土弦杆和空不锈钢管腹杆纤维梁宏观尺度模型，节点区域不锈钢管和核心混凝土分别采用壳单元和实体单元建立微观尺度模型，采用多点约束方程实现不同尺度单元之间的耦合，构建了曲线形不锈钢管混凝土桁架结构一致多尺度非线性有限元模型。应用该模型进一步分析结构荷载-变形全过程关系曲线的特征，桁架结构局部损伤演化、应力应变分布、不锈钢管与混凝土相互作用以及杆件传力机制等受力机理。在直不锈钢管混凝土桁架结构抗弯刚度和承载力计算方法的基础上，通过参数分析，提出了曲线形不锈钢管混凝土桁架结构抗弯刚度、抗弯承载力计算方法，并提出了相应的弦杆及腹杆设计方法。本研究可为曲线形不锈钢管混凝土桁架结构的应用和设计提供参考。