Simulation study on anti-shear performance and structural mechanical response of assembled composite beam

Abstract

With the development of national economy, the requirements for traffic structure facilities are increasing, which need to meet the increasing demand of traffic load while minimizing the adverse impact on traffic and environment during the construction cycle. The assembled structure not only has the characteristics of energy saving and environmental protection, which can reduce the pollution caused by the construction site during the construction period, but also can guarantee the construction quality and meet the demand of traffic load through factory prefabrication, so the assembled structure has been widely used. The assembled composite girder is a new type of structure in bridge engineering, with good mechanical characteristics, and convenient construction and outstanding economy, which fits well with the concept of sustainable development in China. Steel-concrete composite beam is the main structural form of assembled composite beam. When external load is applied, the upper concrete beam mainly bears the pressure, while the lower steel beam mainly bears the tensile force, which skillfully plays the mechanical characteristics of the material. The concrete beam and the steel beam are connected by shear connectors, which are commonly used in the form of bolted connections. However, it is found in the actual project that the common damage point of the bolted assembled beams in the process of use is near the connectors, so it is necessary to study the shear resistance of the bolted connectors of steel-concrete assembled beams. In addition, the analysis of shear joints as part of the assembled composite beams is not comprehensive for the joints alone. Moreover, steel and concrete beams tend to crack as well as yield during service, so it is also crucial to investigate the mechanical response of the overall and local members of the combined girders under load. In the actual service of the combined girder bridge, the shear joints, as the weak link, often cause local damage not only due to cracking of the anchorage points, but also to local bond failure, resulting in the relative slip of the pins and concrete. Based on the above considerations, this paper investigates the bond slip characteristics of concrete and pinned joints. In this paper, the above problem is investigated by ABAQUS, a large commercial finite 吉林大学硕士学位论文 IV element analysis and computational software, based on the consideration of material nonlinearity and contact nonlinearity. The mechanical response of the shear joints under static and dynamic loading is first analyzed; then the damage pattern, seismic performance and ductility of the shear joints are investigated by combining the peg strength, concrete strength and the friction coefficient between the steel beam and concrete block. In addition, the load and deformation analysis of the overall and local components of the steel-concrete composite beam based on shear connectors is carried out by various external load forms, and the evolution trend of stiffness, energy dissipation and ductility of the composite beam under repeated load is also studied. Based on the above study, the following conclusions are obtained: the damage area of concrete block of bolted composite beam is significantly smaller than that of bolted connection under static load; with the increase of concrete strength level, the damage area of concrete block under the same compressive damage condition gradually decreases, and the damage area is concentrated in the area of bolted or bolted connection. With the increase of friction coefficient between steel beam and concrete block, the damage area of concrete block gradually increases. The damage area of the bolted connection mode is slightly higher than that of the bolted connection mode. And the Mises stress of the shear connection gradually decreases with the increase of the friction coefficient. With the increase of repeated load action time, the stiffness of the combined steel-concrete beam degrades continuously and the overall damage energy dissipation rises continuously. The bond damage at the peg-concrete interface mainly presents three stages, namely elastic stage, elastic-plastic stage and elastic-plastic peeling stage, and the change of load form will lead to different deformation of the structure, which will affect the bond at the peg-concrete interface.