Composite Beam Negative Moment Flexural Test And Shear Strength Of Angle Connectors

The steel-concrete composite beam is a new type of composite structure,which consists of shear connectors linking two materials,concrete and steel beams,into one,which gives the two materials full play to their compressive and tensile properties,and compared with the traditional composite beam,it has the advantages of higher the loading capacity and better anti-seismic performance.As a form of steel-concrete composite beam,the composite beam with precast slabs has advantages such as a short building cycle.During the construction of the precast slabs in composite beam,the precast slab needs to be reinforced to enhance the laminated performance.However,precast slab with extruding reinforcement increases the difficulty of shipment and installment,which increases the building cost.In this paper,a kind of angle steel connector embedded in the prefabricated base plate in the stacked plate combination beam is proposed,which aims to replace the traditional prefabricated plate reinforcement by embedding the angle steel connector.According to this,two sets of flexural tests on the composite beam with precast slabs under the action of negative bending moment were carried out,and the variable is whether there is a buried angle steel connector,and two groups of specimens with negative bending moments are compared and analyzed for their load strength.At the same time,due to the embedded position of the connector,it can show good transverse shear resistance.On this basis,a simulation of the transverse push-out test was carried out,and the transverse shear strength provided by the angle connector was investigated.In addition,based on the fact that there are fewer and large differences in the shear strength of angle connectors,the calculation equation of shear strength of angle steel connectors is proposed in combination with the test phenomenon and simulation results.In this paper,the main efforts and findings are as follows:（1）In the negative bending moment bending test,due to the reason of the angle steel connector,the shear connection of the superimposed plate combination beam with angle steel is higher than that of the traditional stacked plate combination beam.This increases the stiffness of the specimen and reduces the slip,but the ultimate bending bearing capacity does not change much.（2）In the bending test,the superimposed surface of the two stacked plate combination beams has never cracked.This shows that,as with traditional laminated panel combination beams,stacked plate combination beams with angle steel connectors can still achieve good overall performance.At the same time,the prefabricated plate with angle steel does not need to be ribbed when making,which is more convenient for the transportation and installation of the stacked plate combination beam.（3）The FEM model established by using ABAQUS software can simulate the flexural strength of the composite beam in negative bending moment conditions and the shear strength of the push-out test more accurately.Composite beams with angled steel connectors have the same good bending resistance compared to traditional reinforced stacked plate combination beams.At the same time,the composite beam did not have cracks in the superimposed surface of the concrete slab during the whole test process,which indicates that the composite beam possesses good integral performance.By welding angle steel connectors to achieve the effect of replacing the reinforcement,so as to facilitate construction and facilitate its promotion.（4）According to the simulation results,the single angle steel connector proposed in this paper can provide a transverse shear bearing capacity of 142.2k N.When the main beam spacing is far away and the lateral connection is weak,the effect of improving the transverse shear resistance of the stacked plate combination beam can be achieved by increasing the angle steel connector of the prefabricated plate.（5）According to the simulation results,the shear strength of the angle connectors is related to the yield strength of the connector and the thickness of the flange.Based on this,this paper proposes an equation for calculating the shear strength of the angle connector on the foundation of the previous research.In contrast to the Chinese empirical equation and the design of foreign norms,the equation’s calculation results are closer to the analog values.At the same time,the standard deviation and coefficient of variation of the formula are the smallest and closest,0.047 and 0.046,respectively.This suggests the reliability of the calculation equation.The test results show that for the two sets of composite beam with precast slabs,the difference between the bending bearing capacity and the ability to resist slip is very small,and the stiffness of the test beam with angle steel is slightly larger.At the same time,the precast slabs with angle connectors can replace the traditional precast slabs with extruded reinforcement and lower the installation cost.In addition,a new equation for calculating the shear strength of the angle connector is proposed,which consider the yield strength of the connector and its flange thickness,which is not uniform in the current national norms.Compared with domestic and foreign normative and empirical formulas,the calculation results of this equation are more accurate and have certain feasibility.Figure [42] Table [5] Reference [66]...