Analysis Of Failure Mode And Bearing Capacity Of Oblique Section Of Reinforced Concrete Beams Indirectly Loaded By Fire

In actual structural engineering,the load on many reinforced concrete beams is not directly applied on the top surface of the beam,but is transferred to the web of the main beam as its bearing through the secondary beam.This loading method is usually called the indirect loading method.The research shows that the load-bearing performance of the oblique section of the beam under the indirect loading method is more unfavorable than the direct loading method.However,under the effect of thermal-mechanical coupling or after fire,due to the deterioration of material properties,the shear resistance of the reinforced concrete beam by indirect loading may be further weakened.Therefore,it is of great theoretical and practical significance to carry out the research on the shear behavior of oblique section of reinforced concrete beams under thermal-mechanical coupling and after fire.There are few research results in this field at present,this article will study the load-bearing performance of the oblique section of reinforced concrete beams under thermal-mechanical coupling and after fire.To explore the calculation method of the oblique section bearing capacity by indirectly loading reinforced concrete beams under thermal-mechanical coupling and after fire.(1)Firstly,it analyzes and summarizes the main domestic and foreign research results of the mechanical and thermal properties of steel and concrete materials under and after high temperature.It analyzes the shear bearing theory of oblique section of beam under direct and indirect loading,and the influence of position changement of secondary beam along the main beam section to the shear bearing capacity of the oblique section of the beam.(2)It briefly introduces the completed experimental research process and results of the shear bearing capacity of the oblique section of the reinforced concrete beam under indirect loading under fire.It analyzes the bearing mechanism and failure mode of the test beam,which has the foundation for the experimental research for the analysis of the shear capacity of oblique section the reinforced concrete beam under the thermal-mechanical coupling and indirectly loaded reinforced concrete beam.(3)Drawing on the calculation model of shear bearing capacity of oblique section directly loaded reinforced concrete beams at room temperature,a calculation model of shear bearing capacity of the oblique section which indirectly loaded under the thermal-mechanicalcoupling and after fire is proposed.Based on the compressive shear strength criterion of concrete at room temperature,the compressive shear strength criterion of considering the influence of fire on concrete was established and then the calculation method of the shear capacity of the diagonally loaded beam under thermal coupling and after fire was established.Analyzed and compared with the test results.(4)It calculates and analyzes the change trend of the ultimate load of the beams based on the shear capacity and the flexural capacity of the reinforced concrete beams under thermal-mechanical coupling and after fire,and discusses the indirect loading designed under the "strong shear weak bending" at room temperature.Whether the beam still meets this design principle under the thermal-mechanical coupling and after the fire,the calculation and analysis results show that the reinforced concrete beam under the thermal-mechanical coupling and after the fire indirectly loads still meets the design principle of "strong shear weak bending".