Study On Mechanical Properties Of Simply-Supported Composite Beams Considering Creep And Slip

In the current industry,steel-concrete composite structures are widely used in bridges and super high-rise building structures due to their excellent overall performance.In addition,the ’guidance’ issued by the Ministry of Transport in 2016 also clearly pointed out that the construction of bridge structures such as steel box girders,steel truss girders and steel-concrete composite girders should be strengthened in the future.The creep effect of concrete and the slip effect of shear connectors between interfaces in steel-concrete composite structure will have adverse effects on the composite structure,thus affecting the safety of bridges or buildings.Therefore,it is necessary to study the creep and slip effects in composite beams.In this paper,the mechanical properties of steel-concrete composite beams under creep and slip coupling are further studied.Firstly,based on the energy variational method and the principle of minimum potential energy,the energy equation of composite beams considering creep and slip coupling is established by introducing basic assumptions,and the second-order differential equation of axial force of steel-concrete composite beams is further derived.Then,by using different boundary conditions,the formulas for calculating the axial force,deflection and slip of simply supported composite beams under uniform load and concentrated load in the middle of span are obtained.Secondly,the creep criterion in ANSYS finite element software is used to simulate the creep effect of composite beams with time-varying concrete material parameters,and the slip effect of composite beams is simulated by selecting appropriate elements.Then the two are combined to verify the correctness of the calculated values and numerical simulation values.Finally,by analyzing the factors affecting the mechanical properties of composite beams,a general conclusion is drawn.The influencing factors include the strength of concrete,environmental humidity,stud stiffness,stud spacing and the section size of steel beam.The results show that the error between the calculated value of the formula derived in this paper and the numerical simulation value is very small,which can be applied to engineering calculation.Simply supported composite beams considering both slip and creep effects will have a significant impact on the structure and should not be ignored in engineering structures.The higher the concrete strength grade,the greater the environmental humidity,the smaller the influence of the creep effect of concrete in the composite beam on the composite beam.The greater the stud stiffness,and the greater the influence of the creep effect of concrete in the composite beam on the composite beam.The creep effect will lead to the stress redistribution of the composite beam section,which will reduce the bending moment and axial force in the concrete slab and increase the bending moment in the steel beam.The research results can provide a theoretical basis for the calculation of mechanical properties of composite beams considering the coupling of slip and creep in practical engineering.