Experimental Research On Mechanical Of Reinforced Concrete With Sustained Axial Load After Exposure To High Temperature

More attention has been focused on fire resistance of buildings since1980s. Researchers mainly investigated the behaviors of concrete under high temperatures and fire resistance as well as mechanical properties of un-loaded concrete members and structures in fire. However, due to limitation of test facilities, little research work considered the effects of the initial loads during the tests. It did not comply with the actual loading condition of structures under fire. The mechanical properties of un-loaded concrete after high temperature could not be used to reasonably evaluate the mechanical properties of reinforced concrete structures after the interaction of high temperature and stress. So reasonable damage assessment and repair scheme have not yet be put forward to provide references for reinforced concrete structures after high temperature. Therefore, in this paper, the mechanical properties of axially restrained reinforced concrete after high temperature were studied and the main work was summarized as follows:(1) Tests on temperature distributions of specimens heated by an electric furnace were carried out and section temperatures were tested by using built-in thermocouples during the fire exposure and cooling phase. And temperature field was numerically simulated by ABAQUS in cases of heated by electric furnace during the fire exposure and cooling phase. An equivalent heating regime was established using the method of the temperature field test combined with the finite element simulation and was proved feasibility by contrast test and numerical analysis.(2) Experimental study on mechanical behaviors of concrete with axial load during the entire high temperature exposure was carried out. The experimental study mainly focused on the effects of axial load level and high temperature on residual compressive strength, modulus of elasticity, stress-strain relations of concrete after high temperature.(3) Experimental study on mechanical behaviors of reinforced concrete columns with axial load during the entire high temperature exposure was carried out. The experimental study mainly focused on the effects of axial load level, high temperature as well as cooling regimes on residual axial bearing capacity, axial stiffness as well as ductility of fire-damaged reinforced concrete stub columns after high temperature.(4) Reasonably selecting constitutive relation models and residual compression strength models, mechanical behaviors of reinforced concrete were numerically simulated by MATLAB programme. The effects of axial load level on mechanical behaviors of reinforced concrete were analysed.