【作者】 霍静思；

【导师】 韩林海；

【作者基本信息】 福州大学 ， 结构工程， 2005， 博士

【摘要】 随着钢管混凝土结构在实际工程中应用的日益增多,深入研究其火灾后的力学性能和损伤规律显得愈来愈重要,但以往国内外对该方面的研究尚少见报道。本文研究钢管混凝土结构节点在火灾作用后的力学性能和实用计算方法,具体进行了以下几个方面的工作: (1) 进行了火灾作用后钢管混凝土轴压和纯弯构件的力学性能的实验与理论研究,分析了火灾后钢管混凝土轴压和纯弯构件荷载-变形全过程关系曲线,理论结果与实验结果总体上吻合较好。采用理论分析模型,对影响火灾后钢管混凝土轴压和抗弯承载力、轴压刚度和抗弯刚度的影响因素进行了分析,在此基础上推导出轴压和抗弯承载力、轴压刚度和抗弯刚度实用计算方法。(2) 首次进行了一系列火灾作用后钢管混凝土柱-钢梁节点在恒定轴压力和往复水平荷载作用下滞回性能的实验研究。试件的升温按国际标准化委员会标准ISO-834和我国《GB9978-88 建筑构件耐火实验方法》所规定的建筑火灾标准升温曲线进行。通过实验,研究了常温下和火灾后、不同梁柱线刚度比和轴压比情况下、以及常温下与经修复后节点的力学性能变化规律。(3) 在确定了高温后钢材和混凝土材料本构关系模型、以及结构构件截面温度场的基础上,本文提出了可计算火灾作用后钢管混凝土结构节点在单调和往复加载情况下荷载-位移关系的理论分析模型,该模型考虑了结构在荷载作用下的物理和几何双重非线性。算例分析结果表明,该理论模型的计算结果与实验结果总体上吻合较好。(4) 利用所提出的理论分析模型,对影响火灾作用后钢管混凝土柱-钢梁节点P-? 关系的影响因素,如长细比、截面尺寸、含钢率、梁柱线刚度比、梁柱弯矩比、轴压比和受火时间等参数进行了分析。在此基础上推导出了火灾作用后节点的承载力,以及P-?恢复力模型的简化计算方法。更多还原

【Abstract】 With the increased use of concrete-filled steel tubular columns in building structures, it is becoming more and more significant to further the research studies on the mechanical behaviour and potential damage after exposure to fire. But there is very little research work on postfire behavior of this kind of structure at home and overseas. The paper describes the research studies on the mechanical behaviours and practical calculation on concrete-filled steel tubular structural connections after exposure to fire. The main achievements can be summarized as follows: (1) The paper presents theoretical and experimental studies on the axially loading and flexural bending behaviours of CFST members after expure to fire. The load versus deformation relations, which is on the whole in good agreement with tested results, of the CFST members under axial loading or flexural bending moment after fire was analyzed theoretically. The theoretical model was used to analyze the potential factors influencing the compression resistance, the bending moment capacity, axial stiffness and flexural stiffness of CFST after fire. On the base of the parametric analysis, the practical calculation of the postfire compression resistance, bending moment capacity, axial stiffness and flexural stiffness was obtained. (2) A series of experimental study on the hysteretic behaviour of steel beam to concrete-filled steel tubular column connections after exposure to fire were conducted for the first time under combined constant axial load and cyclically increasing flexural load. The specimens was heated following as closely as possible the ISO-834 standard fire curve or the standard fire curve prescribed by the Regulation of GB9978-88 (Structural Member Fire-Resistant Experimental Method). According to the experimental results, comparisons was made with the changing mechanical behaviours of the joints between at ambient temperature and after fire, under different beam-column stiffness ratios and different axial load levels, and between at ambient temperature and after repaired. (3) Based on the determinated stress-strain relations for steel and concrete after high temperatures and the temperature fields in the structural member, a finite element model, in which geometrical and material’s nonlinearity are taken into account silmultaneously, was presented to calculate the load versus deformation relations of CFST connections after exposure to fire under monotonic and cyclic loading. With the validation of relative exemples, the calculated results using the FEA model are on the whole in good agreement with the experimental results. (4) Based on the theoretical model, the influences of the slenderness ratio, sectional dimension, steel ratio, beam-column stiffness ratio, beam-column moment ratio, axial load level and fire duration time on the P-? relation of the steel beam to concrete-filled steel tubular column connection after exposure to fire are discussed. The load bearing capacity and the simplified method for calculation of the P-? hysteretic model of the joint after exposure to fire is put forward based on the parametric analysis results.更多还原