Large Span Concrete Filled Steel Tubular Arch Bridge Dynamic Characteristics Of The Composite Element Method

With the merits of high strength, long spanning ability, good seismic behavior and convenience of construction, the concrete-filled steel tubular (CFST) arch bridges have become commonly used in recent decades. However, the research work on CFST arch bridges is not far more enough, especially in the dynamic analysis.In this thesis, the arch rib of CFST arch bridges is firstly discetized into the curved beam element. Reasonable spatial displacement models of the curved beam element are conceived and the elemental stiffness matrix and mass matrix of such a curved beam element are also derived. Secondly, a new compound element for arch bridges is constructed. Such a compound element is composed of different structural elements of arch bridges such as suspenders, floor beams and arch ribs (curved beams). Based on the energy principle and the forming matrix method proposed by Professor Qing-Yuan Zeng, the stiffness matrix and mass matrix of such a compound element are derived in details in the thesis. The corresponding Matlab-based computer software is developed. Lastly, the proposed compound element formulation is used to carry out the dynamics characteristics analysis of the Ji An CFST arch bridge in Jangxi Province, China. Meanwhile, the dynamics characteristics analysis of the same bridge is carried out by the commercial finite element software Ansys and field ambient vibration testing. Both frequencies and mode shapes of the bridge are obtained and compared. The obtained results agree well. In such a way, the proposed compound element method for arch bridges is verified.It is demonstrated that the proposed compound element method for arch bridges has many advantages such as less element numbers and enough accuracy. It is easy to obtain the global dynamic behavior of CFST arch bridges. More importantly, it is expected that this method can be an effective approach for the further dynamic response analysis of CFST arch bridges under all kinds of dynamic loads such as earthquakes, winds and vehicles.