Finite Element Analysis And Research On Fire Resistance Of Reinforced Concrete Structures

Reinforced concrete structure in its life cycle, could face the threat of fire. Building fire caused huge economic losses and casualties every year. Research on high temperature performance of reinforced concrete structures and components is the basis for building structure fire resistance design and post fire structural repair and reinforcement and damage assessment. Among them, the temperature distribution within the structure and high temperature mechanical response of the whole structure under fire are intense and complex, It is affected by many factors, the research results exist a large discreteness. For a long time, fire researchers conducted in-depth research on the fire resistance of structures, that the important problem in the field of structural engineering. Because of the long period, high cost and difficult operation of fire test, making use of numerical simulation software analysis of the high temperature performance of reinforced concrete structure and components becomes particularly important. This article on the basis of predecessors’ theory and experimental study and finite element analysis software ABAQUS platform, to study the temperature field and mechanical properties of reinforced concrete beam, column and frame structure subjected to fire. The research achievement mainly includes:(1) Based on the thermal characteristics and high temperature stress-strain constitutive relation of steel and concrete, using ABAQUS to simulate the section temperature field distribution and deformation process of reinforced concrete beam subjected to fire. The dominant factors of affecting the section temperature field is analyzed, and study the influence of parameters on the high temperature mechanical properties of reinforced concrete beam, such as the cross section size, protective layer thickness, span ratio, load ratio, reinforcement ratio. The results showed that the fire way, aggregate type, and the time of fire had a significant influence on the temperature field of the beam section, and the effect of the section size on the temperature field of the beam section was relatively small. There will appear a obvious turning point between 100℃~200℃ by considering the influence of moisture content on the temperature curve of each points in the beam section. The cross section size, the thickness of the protective layer, span ratio, load ratio and reinforcement ratio have a great influence on ultimate bearing capacity of the beam under high temperature.(2) The reinforced concrete column as an important bearing component of structure, Its fire resistance under high temperature has a great influence on the fire resistance of the whole structure. In this paper, combined with the thermal property and high temperature stress-strain constitutive relation of the steel and concrete materials. Numerical simulation was made for reinforced concrete column by fire. Analysis of section temperature field distribution characteristics of reinforced concrete column under fire. To study the influence of parameters on the high temperature mechanical properties of concrete column, such as section size, reinforcement ratio, axial compression ratio, slenderness ratio, load eccentricity ratio. The results show that the above parameters have a great effect on deformation and limit bearing capacity of the column under high temperature.(3) Establish a single layer double span reinforced concrete frame model, and using ABAQUS finite element method to conduct heat-structure coupling analysis. In different fire conditions, to study the temperature field distribution characteristics and change law of internal force and deformation of beam and column members and whole structure. Results show that frame structure under the two different fire cases of the single span and double span of the fire. The temperature field of the double span beam and side column under fire is the same as that of single span under fire, and the temperature distribution of the central column and the joint core area is different. The temperature of the joint core area is obviously lower than that of the surrounding beam and column. The fire way and axial compression ratio of frame column plays a significant role in high temperature mechanics response of frame structure.