# Study on Mechanical Properties of Simply-Supported Composite Beams Considering Creep and Slip
## 1 Introduction
Therefore, different elements should be selected to simulate various element components in steel-concrete structures, such as concrete, connectors, and steel beams. At the same time, the slip between concrete and steel beams and the concrete cracking in the negative moment zone of continuous composite beams should be considered. Therefore, most of the tests focus less on theoretical analysis for the study of steel-concrete composite beams. In 1997, [PERSON] et al. [28] proposed a two-dimensional nonlinear finite element differential method based on the principle of virtual work to simulate simply-supported beams and continuous composite beams. In 1998, [PERSON] et al. [29] proposed a new finite element method for composite beam elements with an unknown force. The Hermitian interpolation polynomial was used to cause the curvature to be linearly distributed, which reduced the solution's accuracy to a certain extent. Therefore, the force-based model was more accurate than the displacement-based model. In 1999, [PERSON] et al. [30] further proposed a four-node element in which each node has three degrees of freedom in the composite beam element. This assumption is different from other models in that the shear connector transfer is considered to be discontinuous and to fit the actual engineering state better. In 2000, [PERSON] et al. [31] established an inelastic element based on the hybrid method. They analyzed the action of partially shear-connected composite beams under monotonic and cyclic loads. The model assumes that the spring is located at the element's end, and the connection force is assumed to be linearly distributed within the element. In 2003, [PERSON] et al. [32] adopted the double-layer beam element analysis method, which regards the shear connector as a particular beam element. The two ends are rigidly connected with the steel beam and concrete to ensure that the two are bent together. [PERSON] et al. [33] used the shear connector of the cantilever beam element to artificially increase the cross-sectional area of the connector to avoid excessive vertical deformation between the steel beam and the concrete slab. [PERSON] [34] and others began to use spring elements to simulate shear connectors. Concrete and steel beams use three-dimensional solid elements to analyze composite beams' deformation and elastic bearing capacity. In [PERSON] et al. 's work [35], the viscoelastic response of four steel concrete composite beams affected by changing environmental conditions was studied using a finite element model. The simulation results were basically consistent with the current formula, proving the applicability of the finite element model. In [PERSON] et al. [36], the effects of crack separation and the bridge area on the tensile behavior of concrete were studied experimentally and numerically through the Brazilian tensile test. The visually observed failure process gained through numerical Brazilian tests was found to be very similar to that obtained through the experimental tests. [PERSON] et al. [37] established a finite element model (FEM) of simply-supported composite slabs while considering the impacts of non-uniform shrinkage, cracking in the concrete, and the creep of the concrete; then, the reliability of the FEM was verified against the experimental data in the literature. In summary, there are many experimental and theoretical studies on the slip problem of composite beams and the creep problem of concrete, proving that the study of slip and creep in the study of composite beams is very important. However, there are few studies on coupled creep and slip effects in composite beams. Most of the articles that have studied the creep of composite beams assume that the shear stiffness tends to infinity and ignore the effect of slip, but the results calculated in this way are subject to error. There is no formula for composite beams' internal force and deformation considering the coupling calculation.