温度冲击作用下钢管混凝土界面特征与性能优化

发布时间：2018-03-03 10:45

  本文选题：钢管混凝土　切入点：温度冲击　出处：《武汉理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：钢管混凝土是在钢管内浇筑混凝土且由钢管和混凝土共同承担荷载的构件。其优异性能依赖于钢管与混凝土间的复合增强作用,钢管对核心混凝土的套箍作用提高了混凝土的塑性和延性,增加了钢管的整体和局部的稳定性。然而,钢材和混凝土的热工性能差异明显,这导致在服役环境下钢管混凝土界面产生脱粘和脱空现象,影响钢管混凝土的工作性能与结构安全。本文结合温度冲击试验、有限元数值分析方法、热弹性力学理论、非线性拟合理论等,完成了温度冲击作用下钢管混凝土截面温度场、界面性能与界面优化理论等方面的研究工作。研究成果形成了基于核心混凝土膨胀性能精细化设计的钢管混凝土界面优化方法。主要研究内容如下:(1)开展钢管混凝土温度冲击试验研究。试件的长径比、径厚比、套箍指标、材料强度等重要参数能够满足工程实际中的构造要求,试验结果能够较好的反应实际钢管混凝土构件的服役状态。得到了试件截面温度场分布和变化规律,结果显示钢管和混凝土界面存在温度差,有限元分析中需考虑钢管与混凝土界面的接触热阻作用。可运用实测温度场与后期有限元模拟温度场进行对比,以校验有限元模型的有效性和精确性。(2)进行钢管混凝土温度冲击和热力耦合有限元分析研究。建立了有限元分析的试件传热模型和力学模型,并探讨了钢管混凝土温度冲击和热力耦合有限元分析理论。数值计算得到了截面温度场、界面响应和补偿温度引起的界面间隙所需的混凝土自由膨胀率。对比分析了实验温度场和计算结果,结果表明可以利用有限元模型进行钢管混凝土界面特征的参数化分析和界面性能优化设计。试件截面最大非线性温差可达18.2℃,降温阶段钢管Mises应力和混凝土径向应力可分别达36.6MPa、-3.39MPa,环境温度升高将劣化试件界面性能,适量的膨胀率掺量可缓解界面脱空和提高承载力,超过0.5Nu可使钢材和混凝土产生的相对变形弥补温度冲击实验中温度变化引起的界面间隙,超过0.7Nu导致钢管进入屈服阶段且其承载力有所下降。(3)提出了钢管混凝土界面优化设计方法,建立了补偿温度冲击引起的界面间隙所需的混凝土自由膨胀率公式,,,。首先,提出利用钢管混凝土膨胀性能设计来实现钢管混凝土界面优化。然后,采用Python语言编写了参数化分析程序,进行了270个不同几何尺寸和温变条件的未添加膨胀剂的钢管混凝土温度冲击数值分析,分别得到构件所对应的最大界面间隙,并换算得到补偿界面间隙所需的混凝土自由膨胀率。最后,利用270个自由膨胀率离散数据拟合得到混凝土自由膨胀率公式。
[Abstract]:Concrete-filled steel tube (CFST) is a kind of concrete filled steel tube, whose excellent performance depends on the composite reinforcement between steel tube and concrete. The hoop effect of steel tube on the core concrete improves the plasticity and ductility of concrete, and increases the overall and local stability of the steel pipe. However, the thermal properties of steel and concrete are obviously different. This leads to the phenomenon of debonding and voids at the interface of concrete-filled steel tube (CFST) in service environment, which affects the working performance and structural safety of CFST. In this paper, combined with temperature shock test, finite element numerical analysis method, thermo elastic mechanics theory, The temperature field of concrete filled steel tube (CFST) section under the action of temperature shock is completed by nonlinear fitting theory. Research work on interface performance and interface optimization theory. The research results have formed a concrete filled steel tube interface optimization method based on the fine design of core concrete expansion performance. The main research contents are as follows: 1) Steel tube mixing. Experimental study on temperature shock of solidified soils. Ratio of length to diameter of specimens, The important parameters, such as diameter thickness ratio, hoop index, material strength and so on, can meet the construction requirements in engineering practice, and the test results can better reflect the service state of concrete filled steel tube members. The distribution and variation law of the temperature field of the section of the specimen are obtained. The results show that there is a temperature difference between the steel tube and concrete interface, and the contact thermal resistance between the steel tube and concrete interface should be considered in the finite element analysis. The measured temperature field can be compared with the later finite element simulation temperature field. By checking the validity and accuracy of the finite element model, the coupled finite element analysis of temperature shock and thermal mechanism of concrete-filled steel tube (CFST) is studied. The heat transfer model and mechanical model of the finite element analysis are established. The finite element analysis theory of temperature shock and thermal-mechanical coupling of concrete-filled steel tube (CFST) is discussed. The temperature field of section is obtained by numerical calculation. The free expansion rate of concrete required for interface gap caused by interface response and compensation temperature is compared and analyzed. The results show that the finite element model can be used to parameterize the interface characteristics of concrete-filled steel tube (CFST) and to optimize the interface properties. The maximum nonlinear temperature difference of the specimen section can reach 18.2 鈩，

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