Experimental Research On Shear Behavior Of Reinforced Concrete Restrained Beams At High Temperature

In the process of application,buildings will not only face the damage caused by the earthquake,but also face the threat of fire that may occur at any time.Once a fire breaks out,if the building structure cannot undergo the safety test of high temperature damage,it will inevitably lead to enormous socio-economic losses and casualties.In recent years,building fire cases around the world have shown that high temperatures often lead to a decrease in mechanical properties of building materials,cracking of concrete and softening of steel bars,and finally cause sudden collapse of the building.In this paper,the mechanical properties of the beam before and after the fire are tested.The full-scale test pieces are used for the experimental study.The fire resistance of the restrained beams under different shear-to-span ratios(1.2,2.0 and 3.4,respectively)is carried out.Through the fire test under the condition of constant beam temperature of the restraint beam,the temperature field distribution along the section of the restrained beam under fire,the change of the temperature of the steel bar with time,the curve of the beam deflection time,the shear failure mode of the beam and the fire resistance limit are obtained.Through the residual mechanical properties test of the constrained beam after fire,the load-deflection curve,residual shear capacity,residual stiffness and shear failure morphology of the restrained beam are obtained.Contrast and analyze the influence of constraints on the fire resistance,residual shear capacity and stiffness of reinforced concrete beams.The results show that the greater the shear span ratio under fire is,the more severe the redistribution of internal force is;the effect of shear-span ratio on the stiffness of the restrained beam is greater than that of temperature;the refractory limit of reinforced concrete restraint beams with the same shear span ratio is greater than the fire endurance of the simply supported beam;the residual stiffness of the reinforced concrete beam is higher than that of the simply supported beam,and the shear-span ratio is small,and the reinforcement of the residual stiffness is more obvious.Figure62;Table26;Reference 47...