【作者】 王娜；

【导师】 张文福； 吴国忠；

【作者基本信息】 大庆石油学院 ， 防灾减灾工程及防护工程， 2003， 硕士

【摘要】 由于钢管混凝土构件具有良好的抗火和抗震性能，在实际的工程中得到越来越广泛的应用。目前，国内外学者对钢管混凝土在常温下的力学性能研究已经比较广泛，但对其火灾后的抗震性能研究相对比较少，这使受火后钢管混凝土结构的修复、加固没有充分的理论依据。随着钢管混凝土结构在高层建筑中越来越广泛的应用，研究火灾后钢管混凝土结构的力学性能具有实际的工程意义。 本文主要研究方形与矩形钢管混凝土的力学性能。 本文主要研究工作为： 第1部分．采用有限元法分析四面均匀受火的方形与矩形钢管混凝土柱的温度场，编制了相应的计算程序，分析了截面尺寸、含钢率、防火涂料保护层厚度对方形和矩形钢管混凝土温度的影响，并比较了面积相同情况下方形和矩形钢管混凝土中心点的温度。研究表明，随着钢管混凝土截面尺寸的增大，截面内温度场降低；含钢率对钢管混凝土截面内温度场影响不是很大，如果方钢管混凝土核心混凝土的面积确定，则钢管壁厚对截面温度几乎没有影响；随着防火涂料保护层厚度的增大，截面内温度场大幅度降低；在截面面积相同的情况下，随着钢管混凝土截面面积的增大，中心点的温度逐渐减小；矩形钢管混凝土中心点的温度比方形钢管混凝土中心点的温度高；这主要是因为四面受火的矩形钢管混凝土短边方向传热途径较短，传热较快，从而导致其温度升高；随着钢管混凝土截面面积的增大，方形和矩形核心混凝土中心点的温度的差值也越来越大。 第2部分．选择了高温作用后钢管和核心混凝土的应力—应变关系；采用数值计算方法计算了钢管混凝土构件弯矩—曲率全过程曲线，通过对计算结果的分析，得到了常温下矩形钢管混凝土极限承载力的简化计算公式；通过与常温下极限承载力的比较，得到了高温后裸方钢管混凝土、防火涂料保护层方钢管混凝土、混凝土保护层方钢管混凝土的极限承载力影响系数Ψ的公式以及混凝土保护层矩形钢管混凝土的极限承载力影响系数Ψ的简化公式，通过模拟回归，得到了方钢管混凝土简化弯矩—曲率关系曲线的数学表达式，并给出了受火后钢管混凝土抗弯刚度的简化计算公式。分析结果表明：在面积相同的情况下，矩形钢管混凝土的抗弯承载力随着长宽比的增大而增加，但要保证有足够的侧向支撑；火灾后裸钢管混凝土的抗弯承载力影响系数Ψ只与截面尺寸、受火时间有关，加保护层(防火涂料或混凝土保护层)的钢管混凝土的抗弯承载力影响系数Ψ还与保护层厚度有关。 第3部分．采用时程分析法计算框架的水平地震作用，采用层间剪切模型作为所计算框架的力学模型，采用Newmark积分方法求解动力方程，并编制了相应的程序；给出了钢管混凝土柱P—Δ骨架曲线的简化公式，确定了其主要参数(弹性刚度、屈服荷载、屈服位移)，以供地震反应计算时所用，采用双线性滞回模型；利用所编制的程序计算了三个框架(8层、12层和16层)的弹塑性地震反应。分析表明：所给出的侧向力—位移简化公式所得结果与数值计算结果吻合良好，可以作为计算框架弹塑性地震反应的基本数据；所设计的三个框架在火灾前后都能够满足大震不倒的抗震要求；从三个框架火灾前后的地震反应分析得到；在常温下，对于质量和刚度比较均匀的框架结构，在地震作用下薄弱层发生在轴压比较大的底部两层；受火后一般薄弱层在底部两层和受火层，对于容易发生火灾的层要加强防火设计，以保证结构在发生火灾后不会造成太大的损失；从时程曲线中分析得到的薄弱层与极值响应图得到的薄弱层的结果基本一致，可以用这两种方法中的任一种来判断薄弱层。 本文的研究成果可为火灾后方钢管混凝土框架的抗震设计以及震后的加固、修复提供依据，并为深入开展火灾后钢管混凝土框架抗震性能的研究奠定了基础。更多还原

【Abstract】 Concrete-filled steel tube (CFST) members are applied in practical engineering more and more widely due to their excellent fire resistance and earthquake resistance properties. At present, mechanical behaviors of CFST at ambient temperature have been studied widely by Researchers both civil and abroad, but the researches about earthquake resistance properties of CSFT after fire are comparatively less, consequently, There are no sufficient academic backgrounds for strengthening and retrofitting of CSFT structures. With the widely use of CFST in high-rise buildings, there are practical engineering backgrounds to investigate CFST’ s mechanical behaviors after fire.Mechanical behaviors of square and rectangular CFST columns are investigated in this paper. The main investigations are summarized as follows:Part 1. Finite elements method is adopted to calculate temperature field of square and rectangular CFST sections, which is subjected symmetrical fire. Calculating program is developed. Influence of section size, steel ratio and protection thickness to square and rectangular CFST’ s temperature field are analyzed. Temperatures in the center of square and rectangular CFST are compared, whose areas are equal. The following conclusions are obtained: With the section size increasing, temperature fields decrease. Influences of steel ratio to temperature field are little. If the areas of square CFST is fixed on, the thickness of steel has no influence to section temperature. With the protection thickness increasing, The temperatures in section decrease rapidly. In the case of equal section areas, section areas increase, temperature in the center decrease. Temperature in the center of rectangular CFST is higher than that of square CFST. That is because short sides of rectangular CFST transmit heat more quickly. Differences of temperature in the center between square and rectangular CFST are greater with section areas of CFST increasing.Part 2. Stress-strain relations of steel and concrete after high temperature are chosen. The complete moment-curvature curves of CFST’ s members are calculated by numerical method. Mathematical expressions of ultimate capacity of rectangular at normal temperature are obtained. Mathematical expressions of Infection parameter of ultimate capacity of square and rectangular CFST after fire are given. Simplified moment-curvature curve and stiffness of square CFST is obtained. The conclusions are follows: in the case of equal areas, ultimate capacity of rectangular increase with the ratio of length and wideness. Infection parameter of ultimate capacity is related to section size, time of fire and protection thickness.Part 3 Time history method is used to calculate horizontal earthquake effect of frame. Mechanics model is story shear-form model. Newmark’ s integral method is used to solute dynamic equation, and Fortran program is offered. Simplified formula of P桝 framework curve of CFST is provided and make certain main parameters(elastic stiffness, yield load, yield displacement). Bilinear(Double linearity) hysteretic model is adopted. Elasto-plastic earthquake responses of three frames (8-story, 12-story, 16-story) are computed. Theconclusions are follows: The results calculated by simplified formula of P桝 curve is well accorded with numerical results. All the three designed frames satisfied with seismic resistance regulations. Analysis from earthquake responses of three frames, we can draw conclusions: at ambient temperature, weak-stories of structures with even mass and even stiffness locate in bottom two stories. After fire, weak stories usually locate in fire stories. So story of easy catching fire must strengthen design to resist fire. We can judge weak-stories from time history curve or extreme response figures.The achievements in this paper can be used as the basis of seismic design of square CFST frames after fire, and may provide theoretical basis for CSFT frames’ strengthening and retrofitting after fire. The results establish basis for further studying earthquake res更多还原