| Summary: | 博士 === 國立成功大學 === 土木工程學系碩博士班 === 92 === The bridge vibrates when a high-speed train passes. Thus, how to reduce the vibrations induced by high-speed trains is an important issue. In this thesis, a simple finite element model of the moving wheels and cars was developed to simulate the moving high-speed train problems. Then, a three-dimensional finite element method was used to analyze the relationship of resonance between train speed and bridge. The bridge types include multi-simply supported bridge, arch bridge and cable-stayed bridge. According to the finite element results, the resonance is one of the important factors to the bridge vibration. To avoid train-bridge resonance for multi-simply supported bridges, the first dominated train frequency and the first bridge natural frequency in each direction should be as different as possible. If the two first frequencies are similar, the bridge resonance will be very serious. For arch and cable-stayed bridges with long spans, the resonance will produce the maximum response when the train velocity equals 0.88Lf2 and 0.5Lf4, respectively. Thus, the train velocity should be appropriately chosen to avoid train and bridge resonance.
The train speed is generally lower than the Rayleigh speed of soil. If the train moves on a soft ground, its speed may exceed the soil Rayleigh speed, and it may produce large ground vibration. This study used the three-dimensional finite element method to simulate this problem. Additionally, two efficient schemes of the vibration isolation were studied, including the construction of the concrete slab and soil improvement. This thesis aims to find how the building foundation affects the vibration reduction; therefore, dynamic field experiments were performed to investigate this topic. The result of the experiment shows that the foundation slab can significantly reduce the horizontal vibration transformed from soil. But for the vibration isolation of the vertical direction, the reduction is limited.
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