Study On Mechanical Properties Of Composite Reinforced Concrete Columns Under Fire

This thesis mainly studied the mechanical properties of reinforced concrete columns reinforced with thin-walled steel tubes,ring-shaped concrete and CFRP under fire.Based on previous studies,the thermal and thermodynamic properties of concrete,steel,and CFRP are summarized.Based on the standard heating curve,the temperature field and mechanical properties of ordinary reinforced concrete columns and composite reinforced concrete columns were analyzed.On this bases,the effects of fire duration,cover thickness,and stirrup spacing on the temperature field and mechanical properties of reinforced concrete columns and composite reinforced concrete columns were investigated.The main conclusions are listed as follows:(1)The temperature changes of the measured points of ordinary reinforced concrete columns and composite reinforced concrete columns are in good agreement with the actual test data.The temperature field cloud diagram accurately shows the temperature changes of the columns during the fire.After comparison between the two,it is found that the composite reinforced concrete column can effectively block the transmission of heat insulation and reduce the temperature of the reinforced concrete column under the dual protection of steel tube and ring concrete.(2)Through the analysis of the temperature field,it can be found that for the reinforced concrete columns: the fire time and the thickness of the protective layer have an influence on the temperature field distribution,and the change of the hoop spacing has little effect on the temperature field distribution.For composite reinforced concrete columns: the thickness of the ring-shaped concrete,the thickness of the steel tube,and the duration of the fire have an effect on the distribution of its temperature field.The influence of temperature field distribution is small.(3)Through the analysis of the change of its bearing capacity,it can be found that the bearing capacity of the composite reinforcement column gradually decreases with the increase of the fire time,and with the increase of the thickness of the steel pipe and the thickness of the ring-shaped concrete,the composite reinforcement under the same fire time The bearing capacity of the column gradually increases.(4)Put forward a new idea of safety factor,compare and analyze the safety factor of ordinary reinforced concrete columns and composite reinforced concrete columns,and find that the safety factor of composite reinforced concrete columns is greater than that of ordinary reinforced concrete columns,and the corresponding fire resistance time Increased about two times.In addition,the parameters of annular concrete thickness,steel tube thickness,and eccentricity were changed,and the influence law on the safety factor was studied in depth to provide a reference basis for fire rescue workers.