A New Composite Truss Bridge and a Study on Its Dynamic Characteristics with FE and Experimental Methods

Improvements to the dynamic characteristics and stiffness of composite girder bridges are necessary to expand their applications and capabilities. The natural frequency of a bridge directly reflects the dynamic characteristics of a structure. From the calculation principle for the natural frequency, the natural frequencies of a bridge can be significantly increased if the load increases slightly while the structural stiffness increases significantly. Based on this, a new type of concrete-steel composite truss bridge is proposed. The new bridge has a reasonable new arrangement for the position of the concrete and steel, according to the bending moment law for continuous girders. The mechanical analysis of the new bridge shows that it has the characteristic of adding a small amount of load at a reasonable position, which can significantly improve the stiffness. Therefore, it is possible to achieve the purpose of improving the dynamic characteristics so that they are far better than those of a conventional composite truss bridge. To further study the dynamic characteristics of the new composite truss bridge, the finite element (FE) method was used to analyse the new bridges, and the results are compared with those of conventional composite truss bridges. Furthermore, several parameters that influence the dynamic characteristics of the new composite truss bridge were studied. Finally, the dynamic characteristics of the small-span new bridge were studied by finite element analysis (FEA) and experiment. The results show that the new composite truss bridges with different span arrangements and different second-stage dead loads always have better natural frequencies and stiffness advantages. Therefore, the new composite truss bridge is suitable for girder bridges with strict requirements for their stiffness and dynamic characteristics, especially for super-long span high-speed railway girder bridges.