Analysis And Calculation Of The Shear Capacity Of The Oblique Section Of Reinforced Concrete Beams After Fire

Reinforced concrete structures are widely used in building structures.After experiencing fire,the performance of steel and concrete materials deteriorates,which leads to the deterioration of the bearing performance of reinforced concrete members.Therefore,there is important theoretical and practical significance in the research of the remaining bearing capacity of reinforced concrete structures and members after fire.In this thesis,based on the results of the completed experimental research on the shear capacity of the reinforced concrete beams subjected to fire,the shear bearing mechanism and failure mode of the reinforced concrete beams after the fire are analyzed.The results of the research have established a calculation method for the residual shear bearing capacity of reinforced concrete beams after fire.The main research contents and results are as follows:(1)The main research results on the properties of steel and concrete materials affected by high temperature were analyzed and summarized.The process and results of the experimental research on the shear resistance of the inclined section of reinforced concrete beams after fire were briefly introduced,and the bearing mechanism and failure mode of the test beams were analyzed.The analysis laid the foundation for theoretical and experimental research.(2)Based on the experimental research results and referring to the shear resistance mechanism of the reinforced concrete beam diagonal section at room temperature,the load-bearing mechanism and failure mode of the reinforced concrete beam inclined section after fire were analyzed and studied,and the reinforced concrete beam inclined section after fire was discussed.The calculation model and the calculation method of the shear capacity of the reinforced concrete beam oblique section after the fire is established.Then the calculation results are compared with the test results,the error is about 10%,and the calculation results are less than the actual test.As a result,the calculation result is conservative.(3)Based on the calculation and analysis of calculation examples,the relationship between the ratio of the overall bending capacity and shear capacity of the reinforced concrete beams subjected to different fire time based on the bending capacity and shear capacity of beam cross section is discussed.The analysis results show that within 120 minutes of the analyzed fire time,with the increase of the fire time,the reinforced concrete beam designedaccording to the principle of "strong shear weak bending" at room temperature can still maintain.