# Study on Mechanical Properties of Simply-Supported Composite Beams Considering Creep and Slip
## 1 Introduction
[14] from Tsinghua University studied and analyzed the steel-concrete composite beam, deduced the calculation formula of the long-term stress stiffness of concrete, and analyzed the influence of concrete shrinkage deformation on the steel beam section. In 2001, [PERSON] et al. [15] developed an analytical model for the shear-lag effect of composite beams with flexible shear connections, considering concrete's long-term performance, which was established using the virtual work principle. In 2001, [PERSON] et al. [16] analyzed and deduced the calculation formula for internal force redistribution and double constraints in steel-concrete composite beams under the action of concrete shrinkage and creep. The concrete cracking in the negative moment zone of a steel-concrete composite continuous girder bridge was analyzed and discussed through an example. In 2003, [PERSON] et al. [17] established a formula for calculating the stress redistribution of prestressed steel-concrete composite beams under creep and selected a T-beam example for analysis. In 2003, [PERSON] et al. [18] studied the degree of stiffness reduction in composite beams under specific constraints considering the slip effect. In 2003, [PERSON] et al. [19] defined the constitutive interface relation by the Goodman elastic interlayer hypothesis and established the theoretical calculation equation of deflection and slip considering slip and shear effects according to the principle of minimum potential energy and the variational method. In 2004, [PERSON] et al. [20] analyzed and measured steel-concrete composite beams considering the shrinkage and creep effect and the change in load structure in the construction process by using the effective modulus method adjusted by age and the finite element analysis method, and they proposed a new method to calculate the stress redistribution of steel-concrete composite beams under the action of shrinkage and creep. In 2004, [PERSON] et al. [21] established a particular element to consider the slip effect and a finite element analysis model of steel-concrete composite beams under shrinkage and creep effects using the age-adjusted effective modulus method. The long-term stress, deflection, and slip of steel-concrete composite beams were analyzed and calculated. The calculation results were reliable and consistent with the actual values. The creep effects, and the structural stress and strain, were numerically calculated and analyzed. In 2009, [PERSON] et al. [22; 23] studied the composite structure under shrinkage, creep, and cracking. In 2010 and 2016, [PERSON] et al. [24; 25] analyzed composite beams' linear and nonlinear time correlation considering the creep and shrinkage effects of concrete flanges. They gave accurate spatial and temporal discrete deflection solutions considering the slip effect. In 2011, [PERSON] et al. [26] considered the principle of minimum potential energy and the Goodman elastic interlayer hypothesis, and the analytic equation for the stress, deformation, and deflection of composite beam sections considering interlayer slip was derived. In 2019, [PERSON] et al. [27] studied the deflection calculation method of steel-concrete composite beams. The research showed that when the stiffness of the shear connectors was less than 1200 MPa, the additional deflection caused by the interlayer slip effect was more extensive, and the influence on the total deflection was also more significant. The influence of the slip effect on the deflection of composite beams should be considered, and the smaller the shear stiffness, the greater the effect of interfacial slip on the deflection, so it is necessary to consider the combined effects of both concrete creep and interfacial slip on the combined beam. There are many types of research on the finite element analysis of ordinary reinforced concrete beams, but there are few types of research on steel-concrete composite beams. The main reason is that many element forms exist in steel-concrete composite beams.