Study On Mechanical Properties Of Reinforced Concrete Slab-Column Joints Under Fire

Reinforced concrete slab-column structure is composed of floor slab and column,which is widely used in practical engineering because of its advantages of fast construction speed and low inter layer height.However,the weak link of reinforced concrete slab-column structure is slab-column joints,which are prone to brittle failure and consequent continuous collapse of slab-column structure.At present,there are some research results on the mechanical properties of reinforced concrete slab-column structures at room temperature at home and abroad.However,the mechanical properties of slab-column structures at high temperatures are still shallow.Therefore,in-depth study of the fire resistance of slab-column joints has strong engineering application and theoretical significance.In this paper,reinforced concrete slab-column joints and reinforced concrete slab-column structures are studied.The mechanical properties of slab-column joints under fire and the continuous collapse resistance of slab-column structures at room temperature are studied in depth.The main research work is as follows:Firstly,the temperature field analysis of plate-column joints at high temperature is studied.Based on the experiment of Anberel,Ghent University,Belgium,the temperature field analysis of plate-column joints is numerically simulated by using ABAQUS finite element software.By comparing the simulation results with the experimental phenomena and the experimental data,the accuracy of the finite element model is proved.Furthermore,the effects of different heating curves,the fire surface of slab-column joints,the fire time of slab-column joints,the size of column section and the thickness of floor protective layer on the temperature field of slab-column joints are discussed.The simulation and analysis of the temperature field of slab-column joints is an important data basis for the analysis of the thermal-mechanical coupling of reinforced concrete slab-column joints at high temperatures.Secondly,based on the analysis of temperature field of reinforced concrete slab-column joint section,the thermal-mechanical coupling analysis of Anberel's test is simulated by ABAQUS software.By comparing the simulation results with the experimental phenomena and the experimental data,the accuracy of the finite element model is proved.Furthermore,the failure process and failure mechanism of slab-column joints are analyzed,and the law of mechanical decline of slab-column joints under uniform load is obtained.The influence of different fire time,fire surface,section size and reinforcement ratio on the ultimate bearing capacity of slab-column joints is further analyzed.The results show that the time of fire,the reinforcement ratio of floor and the fire surface have greater influence on the ultimate bearing capacity of slab-column joints,while the section size has little effect on the ultimate bearing capacity of slab-column joints.Finally,oblique reinforcement is installed in the neutral layer of slab-column joints to study the improvement rate of punching shear and penetration resistance of oblique reinforcement at high temperature.Based on the analysis of slab-column joints,the finite element model of slab-column structure is established,and the mechanical properties of the slab-column structure after the failure of the middle column and the side column are analyzed and predicted respectively.The results show that the punching shear resistance and penetration resistance of the slab can be improved by setting oblique reinforcement in the slab at high temperature.The oblique reinforcement in the middle of the slab is most suitable when the relative reinforcement ratio is 100%,and the increase rate of penetration time is the most.lt reveals the mechanical properties of slab-column structure with oblique reinforcement and delays the continuous collapse time of column structure,which provides a reference for slab-column structure design.