Study On Physical And Mechanical Properties Of Damage Concrete After High Temperature

When the fire resistance peiformance of concrete is studied, Most studies mainly take the new pouring concrete as the research object, ignore the surface damaged of structure in service processes which may effect on fire resistance of structure. Therefore, it is important to comprehensively considering the relationship between surface damage and temperature and other factors of concrete to get the residual mechanical properties of concrete after fire. It may procides basis for the structure fire resistant design and the restoration and reinforcement of fire structures.This paper researches the residual mechanical properties of the damaged concrete after heating and constant temperature time and different cooling-method. The auther also puts forward the residual stress-strain relation of damaged and undamaged concrete. The specific work of this paper are as follows:(1) Experimental researches were made on the variation of damaged or not concrete quality of different temperature and different constant temperature time and different cooling-method of specimen, obtained the degree of influence of damaged or not of mass loss after the high temperature.(2) Experimental researches were made on the variation of damaged or not concrete mechanical properties of different temperature and different constant temperature time of specimen, the relationship between the corresponding menchanical properties and temperature varying is established. Experimental researches were made on strength and deformation of damaged concrete with different cooling-method, the reason of residual mechanical behavior of concrete cooled by different methods are analyzed.(3) Based on theoretical analysis of damage evolution of the constitutive model of concrete at room temperature,taking the impact of damaged treatment on strength and the temperature weakening effect into account, derived constitutive model of damaded concrete after high temperature.(4) Preliminary assessment component surface temperature after fire.System, this paper introduces several kinds of commonly used to estimate component surface temperature methods, according to the existing data of the compressive strength of concrete after high temperature, the relationship between the strength degradation and temperature is estimated, which can be more convenient and accurately to determine the surface temperature, and lay a foundation for the damage assessment of building structure after fire.