Experimental Research On Fire Performance And Strengthening After Fire Of Key Members Of Industrial Buildings

In order to learn the fire performance of key members of industrial bulidings,,mechanical performance after fire and strengthening method after fire,9 full-scale RC crane beam specimens were subjected to fire test,strengthening test after fire and fatigue performance test,and 5 scale RC lattice column specimens were subjected to fire test and strengthening test after fire.And finite element numerical simulation and theoretical calculation were also made.The main research contents and conclusions are shown as follows:? The fire test was carried out on 7 full-scale RC crane beam specimens and 4 scale RC lattice column specimens.The ISO834 equivalent fire time was 60 min and 90 min respectively.At the same time,ABAQUS finite element software was used to simulate the temperature field.The research shows that the temperature variation trend of concrete and steel bar is consistent with the furnace temperature;the numerical simulation results can reflect the temperature field distribution of the section well;the mid-span deflection of the crane beam specimen changes linearly with the fire time;after fire,the RC crane beam specimens are no failure,in the range of strengthening.? The static load tests were carried out on 5 full-scale RC crane beam specimens,and the crack development,signature load,initial stiffness,material strain,ductility coefficient and failure modes of the specimens were analyzed.The research shows that the bearing capacity and the safety reserve of the fired specimens decrease.the bearing capacity of the strengthened specimens is improved and the deformation capacity is weakened.Different strengthening methods have different degrees of improvement on the bearing capacity of the crane beam specimen.The steel plate strengthening effect is better than the two layers of CFRP sheets.? The fatigue tests were carried out on 4 full-scale RC crane beam specimens,and the relationship between the crack development,the mid-span deflection and the material strain with the number of fatigue cycles and the static performance after fatigue were analyzed.The research shows that the crack development,mid-span deflection and material strain show a three-stage change with the increase of the number of fatigue cycles.The specimens aren't damaged after 2 million fatigue loads,and the static load failure mode isn't changed after fatigue.The unstrengthened specimens after fire are close to failure After experiencing 2 million fatigue loads.The fire effect adversely affects the fatigue properties of the specimens.The fatigue performance of the specimens strengthened by CFRP sheets is improved.? The eccentric compression tests were carried out on 5 RC lattice column specimens,and the initial stiffness,ductility coefficient,load-displacement curve and failure modes of the specimens were analyzed.The research shows that the bearing capacity and stiffness of the fired specimens are significantly reduced;the overall stress of the strengthened specimens is significantly increased,and the bearing capacity,rigidity and deformation ability are significantly improved,exceeding the pre-fire level.? On the basis of considering the fire damage of the material properties,the theoretical calculation formula of the static bearing capacity of both specimens and the fatigue checking formula of the RC crane beam specimens were derived,and the finite element software ABAQUS was used to nonlinearize the force performance.The results show that the theoretical calculation formula can accurately calculate the static ultimate bearing capacity of the fired and strengthened specimens;the calculation results of the fatigue calculation formula are consistent with the experimental results;the load-displacement curves and failure modes analyzed by ABAQUS finite element software are in good agreement with the experimental results.