Natural Dynamic Characteristics And Seismic Response Analysis Of Curved Girder Bridges

Highway interchange is an important component of the lifeline engineering. The failure of highway interchange during a severe earthquake can not only cause the heavy economic losses and casualties but also delay the rescue operations because the communication is broken. In this dissertation, the curved bridge with small curvature radius is researched. The natural dynamic characteristics of out-of-plane vibration of the curved beam and the seismic response of the curved bridge are studied.(1) Based on the force-displacement relationships and the geometrical relationships, the dynamic equations of out-of-plane vibration of the curved Timoshenko beam and the curved Eular beam are deduced using the d'Alembert's principle in this dissertation. Then the improved differential quadrature method (DQM) is applied in solving the out-of-plane vibration of the curved beam, and the processes of this method with simply supported/simply supported and clamped/clamped end are concluded. By using of improved DQM, the natural frequency parameters of curved beams with circular and rectangular cross section are respectively calculated under different conditions of slenderness ratios and central angles and the results are compared with the exact results. The method presented in this paper gives a good accuracy while the numbers of grid points are only limited. At last, respectively according to the Timoshenko beam theory and the Eular beam theory, the effects of shear deformation and rotary inertia on the natural frequencies of curved beams with simply supported/simply supported and clamped/clamped end are researched under different slenderness conditions.(2) A dual-beam stick finite element model is presented to analyze the dynamic characteristics and response of curved box girder in highway interchanges. The modes of the girders are computed respectively based on the discrete 3-D straight beam model, the shell element model and the solid element model. The results are respectively compared with the dual-beam stick model's to evaluate the reliability of the dual-beam stick model. The natural dynamic characteristics of curved box girders with the same radius of circle and different curved length are studied. The contributions of torsion modes to the dynamic response of the curved beam are researched. The influences of the distance between two sticks and the distance between two diaphragms are also researched.(3) The dynamic equations of the curved bridge under the earthquake ground motions of translation are deduced. It is indicated that the structure may rotate across the normal axis under the ground motions of translation. Taking the curved bridge in the trestle of Nanjing Railway Station Square Engineering for example, the natural frequencies of the structure, the Time-History response of the displacements and the internal forces in some key locations are...