ANALYSIS ON NATURAL VIBRATION CHARACTERISTICS OF A RAILWAY STEEL-CONCRETE COMPOSITE BEAM BRIDGE

摘要

Steel-concrete composite beam bridges have a lot of advantages, such as faster construction speed and stronger span ability when compared with concrete beam, and better dynamic and stability performance when compared with steel girders. Due to the relatively small live loads, they are very suitable for medium span bridges in high-speed railway. However, further study is still necessary for the dynamic behaviors of steel-concrete beams. Considering the flexibility of the headed studs between the concrete slab and steel girder, the natural vibration characteristics of a 3-span railway steel-concrete continuous composite beam are studied by finite element model, and then the numerical results are compared with test results. The influence of the connector's shear stiffness on the natural vibration characteristics of the composite beam is emphatically analyzed. The results show that there exist phase differences between the mode shapes of the concrete slab and steel girder. With the increase of the connector's shear stiffness, the lateral, vertical and torsional first order natural frequencies of the composite beam all increase, and the mode shape sequence is changed correspondingly. When the connector's shear stiffness reaches to infinity, all kinds of frequencies become stable, the natural vibration characteristics are just as a beam with no relative slip at the interface between the concrete slab and steel girder.