损伤混凝土高温后的物理力学性能研究

发布时间：2018-05-30 21:05

本文选题：损伤混凝土 + 火灾(高温)　；参考：《西安建筑科技大学》2015年硕士论文

【摘要】：在研究混凝土抗火性能时,大多数研究是以新浇筑的混凝土作为研究对象,忽略了结构在服役过程中表面损伤对结构抗火性能的影响。因此,为了科学、准确评估火灾后结构的残余承载力,必须综合考虑混凝土力学性能与表面损伤、温度以及其他影响因素之间的关系,从而为建筑结构抗火设计和火灾后的结构残余承载力分析及修复加固提供一定的依据。本文对损伤处理的混凝土试件于不同温度、不同恒温时间、不同冷却方式的残余力学性能进行了试验研究与分析,并测出混凝土残余应力—应变曲线,对比分析损伤与未损伤混凝土高温后的残余力学性能的差异。具体工作如下:(1)通过试验对比研究了损伤与未损伤混凝土于不同温度、不同恒温时间及不同冷却方式下的质量变化情况,得出了损伤与否对高温后的质量损失的影响。(2)通过试验对比研究了损伤与未损伤混凝土于不同温度、不同恒温时间后混凝土试件的强度与变形性能的变化情况,根据数据拟合出了高温后相应的力学性能与温度之间的关系。研究了不同冷却方式对高温后混凝土的力学性能的影响情况,分析了高温作用后不同冷却方式下残余性能差异的原因,并根据数据拟合出了不同冷却方式下的残余抗压强度与温度之间的关系。(3)基于常温混凝土的损伤演化本构模型的理论推导,考虑损伤处理对强度的影响以及温度弱化效应,推导了损伤(碳化、冻融)混凝土高温后的本构模型。(4)火灾后构件表面温度初步评定。系统的介绍了几种常用估计构件表面温度的方法,并根据已有的高温后混凝土残余抗压强度的试验数据,建立了高温(火灾)后强度下降系数与温度之间的关系,从而能更方便、准确地对构件表面温度进行判定,为火灾后建筑结构损伤评定奠定基础。
[Abstract]:In the study of the fire resistance of concrete, most of the studies take the newly cast concrete as the object of study, ignoring the influence of the surface damage of the structure on the fire resistance of the structure during the service process. Therefore, in order to accurately evaluate the residual bearing capacity of structures after fire, the relationship between mechanical properties of concrete and surface damage, temperature and other influencing factors must be considered. Thus, it provides some basis for the fire resistant design of building structure and the analysis of residual bearing capacity of the structure after fire, as well as the repair and reinforcement of the structure. In this paper, the residual mechanical properties of concrete specimens treated with damage at different temperatures, different constant temperatures and different cooling methods are studied and analyzed, and the residual stress-strain curves of concrete are measured. The difference of residual mechanical properties between damaged and undamaged concrete at high temperature was analyzed. The concrete works are as follows: (1) the mass changes of damaged and undamaged concrete at different temperatures, different time of constant temperature and different cooling methods are studied by means of experiments. The influence of damage on mass loss after high temperature is obtained. According to the data, the relationship between mechanical properties and temperature after high temperature is fitted out. The influence of different cooling methods on the mechanical properties of concrete after high temperature is studied, and the reasons for the difference of residual properties under different cooling modes are analyzed. According to the data, the relationship between residual compressive strength and temperature under different cooling modes is fitted. (3) based on the constitutive model of damage evolution of normal temperature concrete, the influence of damage treatment on strength and the effect of temperature weakening are considered. The constitutive model of damaged (carbonized, freeze-thawed) concrete after high temperature is derived. Several commonly used methods to estimate the surface temperature of concrete members are introduced systematically. Based on the existing experimental data of the residual compressive strength of concrete after high temperature, the relationship between the strength decreasing coefficient and the temperature after high temperature (fire) is established. Therefore, it is more convenient and accurate to judge the surface temperature of the component, which lays a foundation for the damage assessment of the building structure after fire.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528

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