Study On The Fire Performance Of Reinforced Concrete Frame Structures

Fire is one of the most common disasters. It could cause the collapse of fire architectural structure and harm people's life and properties' safety. Therefore, the fire resistant design of structures is especially crucial. As a result of the integrity of a building's structure, components of a reinforced concrete frame structure have relatively great interaction between each other, and their mechanical properties and isolate members are quite different when they suffer from fire. At present, it is a lack of the research which takes both end constraint and fire resistance of restrained T-beams into account. At the same time, the fire resistance properties of high-level reinforced concrete frames are not discussed deeply.Based on the ABAQUS, this paper established solid element model of the coupling thermal-mechanical of reinforced concrete T-beams and ten layer reinforced concrete frames model based on beam elements separately. Then this paper analyzes the fire resistance properties of constrained components and the framework itself of the reinforced concrete frame structure. In this paper, the main research contents and research results are as followed:(1) According to many scholars' researches about characteristics of steel and concrete materials under high temperature, finite element model of reinforced concrete structure is established. And the coupling thermo-mechanical analysis of reinforced concrete structures is done. Then the results are compared with the existing experiments. The results are in good agreement, thus the thermal and mechanics parameters of finite element calculation model of the reinforced concrete are sum up;(2) A reinforced concrete T-beam is designed and its finite element model are set up. Then though the changes the T-beam constraints, the fire endurance, failure model, deformation feature and redistribution phenomena of internal forces are studied. The results show that with the increase of constraints spring stiffness, the fire resistance limit of constraint beam increases; fire resistance limit within the scope of commonly used engineering is quit different from that of approximate simply supported beams and the beams with fixed direction axial. The boundary conditions should be considered when stress distribution of constraints beam under high temperature is simulated; beam end constraint makes a great influence on stress distribution of T-shaped beam as a whole. The internal force redistribution phenomenon is obvious.(3) A finite element model of reinforced concrete plane frames under local fire high temperature is established. Deformation and failure mechanism, distribution of plastic hinges, development of the internal forces and stress of the frame and fire resistance limit are studied. How the fire location affects the fire resistance performance of plane frame structure is analyzed. The results showed that the top limit of fire resistance of high-level reinforced concrete frame structure is related to fire positions; there are generally two kinds of destruction forms of reinforced concrete frame structure under local fire: one is that underlying framework is destroyed by fire pillar and the lead to the overall destruction of the frame. The other one is that the fire girder of the rest floor structure is so damaged that local structure is damage; the higher floor suffers from fire, the earlier the peak value of axial compressive force of across beam appears, and the smaller the peak value of axial compressive force is The mutual restraint between beam and column has a large effect on the change of axial force of column section.