Study On Three Dimensional Seismic Response Of Frame-Style Curved Girder Bridge With Hinges

Bridges are an important part of highways. When they are destroyed by earthquakes, the economic losses will be huge, the later repairs will be very difficult. More seriously, the damage of bridges will cause traffic paralysis, slow transportation to relief goods and delay to save wounded persons in disaster area. Obviously, it is very hard to estimate the indirect losses which come from the damage of bridges after earthquakes. With the rapid development of human science and technology, bridges with long-span, high-column and complicated structure shape are built and used continually. The dynamic response and nonlinear behavior of these complicated bridges have become the focus of academia and engineering.Frame-style curved girder bridges with hinges are widely used in American highways. The dynamic performance of the bridge in this style is very complicated because it does not only have high columns and long spans, but also contains the structural features of frame and hinge. In recent massive earthquakes, the damage of the bridge in this style was very serious. Therefore, the in-depth study of seismic response for this style will have important academic value, and the research results will greatly meet the demand of engineering background. The seismic response and nonlinear damage process for the bridge in this style are lucubrated in this thesis, based on an example of Yuba curved bridge in California and three dimensional Northridge earthquake waves next to the bridge site. The main research contents and innovative achievements are as follows:1. The establishment method and process of dynamic model for frame-style curved girder bridge with hinges are systematically summarized. The constitutive relation models of concrete and steel are introduced. The simulation theories and methods of nonlinear models for abutment soil springs, abutment shear keys, elastomeric bearing pads are summarized. The nonlinear models of pounding are compared, and Hertz model with hysteresis damping is finally used to simulate pounding elements. The detailed simulation method of hinge is creatively proposed.2. The nonlinear damage process for the span with a hinge and the impact of different longitudinal intervals between the two sides of hinge to damage process are discussed. The detailed model and the simplified model are used to simulate the span with a hinge respectively. The accurate degree and the scope of application for two models are obtained from the computing data of two models. The nonlinear process and damage sequence of elastomeric bearing pads, longitudinal restrained steels, transverse compressive pads, transverse and longitudinal pounding elements, and sections in the root of span with a hinge are researched by Pushover analysis. The longitudinal intervals between the two sides of hinge are changed in detailed model, the impact of different longitudinal intervals and different longitudinal pounding process to the nonlinear damage process of limiting devices in the hinge and the sections in the root of span with a hinge are obtained by Pushover analysis.3. The impact of mass moment of inertia to dynamic characteristic of curved bridge is discussed, and the optimal mass arrangement for curved bridge is confirmed. Four common forms of mass arrangement for the simulation of curved bridge are summarized. Based on eigenvalue analysis, the natural periods of vibration, the fundamental mode, the higher modes of the models with these four forms of mass arrangement are compared to discover the impact of mass moment of inertia to natural vibration of curved bridge. According to the result of nonlinear time history analysis under twice Northridge earthquake load, the impact of mass moment of inertia to displacements of girders, moment-curvature of columns and torques of columns are researched. Finally, the optimal mass arrangement for curved bridge is confirmed by above research results.4. The three dimensional seismic response to integral curved bridge is lucubrated. The impact of vertical earthquake wave to dynamic performance of curved bridge is obtained by comparing the displacements of girders and the moment-curvature of columns under three-dimension earthquake load and two-dimension earthquake load. According to the result of nonlinear time history analysis under three-dimension earthquake load, the seismic responses of girders, columns, abutments, hinges and every limiting device are obtained, the fragile locations in curved bridge are confirmed. The impact of symmetrical arrangement of columns and shortening arrangement of columns to dynamic characteristic of curved bridge are discussed by changing the arrangement of columns.