Numerical Simulation Experimental Research On The Fire Resistance Of The Reinforced Concrete Structure

Since the 20th century, the construction industry has developed rapidly, the reinforced concrete structure occupies more and more proportion in the engineering structure. Reinforced concrete become the first choice of building materials due to the good fire resistance. However, when there is a fire, the mechanical properties of steel and concrete decline with the rising of temperature due to high temperature. In addition, the temperature gradient near the structure increased due to the thermal inertia of concrete, and cross section of component formed the nonuniform temperature field, resulting in the difference of temperature stress and the stress redistribution of the interior of the component, causing structural damage or overall collapse. Therefore, it is necessary and urgent to study the fire resistant properties of reinforced concrete. Based on the national natural science foundation of China, "The fire-resistance research of reinforced concrete structure based on ’residual strength’ thermal damage model (NNSF:51178474)", this paper mainly studies the numerical simulation experiment of full scale reinforce concrete portal frame structure under high temperature. The main contents are as follows:First of all, combined with the research achievements and the status quo of fire resistance of reinforced concrete structure of domestic and foreign literature, analysis the influence factors which influence the fire resistance of reinforced concrete’s structureal, to determine the change rule of the thermal performance and mechanical properties which related to temperature of building materials in the process of numerical simulation.Second, consider change of materials thermal properties and mechanical properties in the process of heating, based on temperature change of standard temperature curve, finite element analysis software ANSYS is applied to the temperature load, aiming at the three temperature levels (600 ℃,800 ℃,1000℃) and three load levels (21kN,28kN,35kN) complied 9 sets of nonlinear analysis program, the temperature changes of structures under fire is analyzed by hot-force-structure coupling analysis, obtained the temperature nephogram and displacement distribution cloud of horizontal and vertical and the stress distribution cloud of the frames under fire, analyzed three dimensional temperature field distribution of the concrete structure, the temperature curves, changes in displacement and stress and strain and so on of the concrete structure after fire, to discuss the fire resistance of concrete structures.Finally, creep simulation experiment was carried out after the fire for the reinforced concrete structures under room temperature, vertical static load was applied in the beam span length L/3 and 2L/3 as creep load and creep total time was set to 8h, creep process is divided into two stages, the initial creep stage and steady-state creep stage,9 sets of nonlinear analysis program were complied to solve and obtain corresponding results. To creep simulation of structures at room temperature, and draw creep curve of reinforced concrete, and then compared with the creep curves of physical experiment and analyze the stress-strain curves, reached relevant conclusions.The study provides an important numerical simulation test basis for the fire resistance of the reinforced concrete research, for relevant in-depth study and application provides the beneficial reference.