Study On Mechanical Behavior Of Steel-Concrete Composite Beam Bridge Considering Interface Slip?shear Lag And Shear Deformation

The steel-concrete composite beam is a new type of laminated beam composed of three parts: a concrete slab,a steel beam and a shear connector.Although it has been widely promoted since its introduction,there are still many technical problems in practical application.For example,there is no uniform calculation method for the ultimate bearing capacity and constitutive relation of shear connectors.The analytical solution method of deflection and stress is not comprehensive,and the calculation process is cumbersome and complicated.In this paper,the simply supported composite beam is taken as the research object,and the effects of slip,shear lag and shear deformation on its deflection and stress are mainly studied.At present,the formulas for the ultimate bearing capacity and the load-slip curve formula for many stud shear connectors have been developed.Through comparative analysis,the calculation method of the ultimate bearing capacity of the stud connectors of the "Code for Design of Steel Structures"(GB50017-2003)that is close to the experimental value and the formula of the load-slip curve of bi-fold lines proposed by Oethlers are selected in the calculation.Simple superposition method,conversion section method and reduction stiffness method are common calculation methods for steel-concrete composite beams.On the basis of these methods,firstly only the effects of the slip are considered,and the control differential equations and boundary conditions are obtained by using the principle of minimum potential energy,then,the formulae for calculating the deflection of a simple-supported composite beam under uniform and concentrated loads are considered when considering only the slip effect.Secondly,on the basis of considering only the equation of slip effect,the theoretical formulas for calculating the deflection of composite beams under uniform and concentrated loads with considering of double effects of slip and shear deformation,double effects of slip and shear lag and three heavy effects of slip,shear lag and shear deformation are derived.Compared with ANSYS results,the compliance is better.At the same time,theoretical analysis was performed on an experimental specimen of composite beams,and load deflection curves,stress of concrete slabs,stress of steel beams,and slip of concrete against steel beams were calculated.The theoretical calculation results are basically consistent with the experimental values and ANSYS simulation results.The correctness of the theoretical formula is explained,and it can be applied to practical engineering.In addition,the parameters of the composite beam deflection calculation formulae under the three effects of slip,shear deformation and shear lag are analyzed.The deflection of the composite beam mainly comes from the elastic deformation and slip effect.The deflection caused by the shear lag effect accounts for less than 1% of the total deflection and can be neglected.When the ratio of beam length to section height is less than 10-15,the deflection caused by the shear deformation effect accounts for more than 10% of the total deflection and should be considered.The wider the concrete slab,the more obvious the shear lag.When calculating the stress of concrete slabs,the influence of shear lag must be considered.