A Study on the Vibrations of Elevated Viaduct Induced by Rapid Transit Train
碩士 === 國立宜蘭大學 === 土木工程學系碩士班 === 97 === The purpose of this study is to analyze the train-induced vibration of bridges and surrounding soils during rapid transit train passing through elevated viaduct. The dynamic load considered is a series of moving axel loads produced by rapid transit train operat...
| Main Authors: | , |
|---|---|
| Other Authors: | |
| Format: | Others |
| Language: | zh-TW |
| Published: |
2009
|
| Online Access: | http://ndltd.ncl.edu.tw/handle/51328426806807525109 |
| Summary: | 碩士 === 國立宜蘭大學 === 土木工程學系碩士班 === 97 === The purpose of this study is to analyze the train-induced vibration of bridges and surrounding soils during rapid transit train passing through elevated viaduct. The dynamic load considered is a series of moving axel loads produced by rapid transit train operating at uniform speed. Because the objective of this study is aiming at the vibration responses of bridges and surrounding soils、therefore、the vibrations of train set、which are judged to have ignorable effects on the responses of the bridge structures、is not considered in this study.
In order to focus on structural dynamic characteristics of the elevated viaduct、the model of bridge structure need to be simplified somehow. Although an elevated viaduct must adapt its configuration to the environmental restrictions、economic considerations often lead to its setup consisted of a series of bridges with almost the same structure configurations. Thus、the starting point of this study is a spatially periodic structure model with every bridge spans having the same structure configuration. And then、a frequency domain structural dynamic analysis scheme based on spatially periodic characteristics is developed in this study. In this analysis scheme、only one characteristic span needs to be modeled using finite elements and formulate the discretized equations of motion using standard FEM assemblage procedures. A set of frequency domain periodic boundary conditions is developed based on the spatially periodic characteristics. Combining these equations of motion and periodic boundary conditions、the dynamic responses of the whole model can be solved. And then、an algorithm for numerical calculation of the dispersion curve of periodic structure can be developed based on the homogeneous equations of motion.
The periodic structure analysis scheme described above is applied to the dynamic response analysis of a typical configurations of rapid transit elevated viaduct structure system. Summarizing the results obtained、the behaviors of train-induced vibrations of the elevated viaduct can be categorized into two types、namely 「Type I」 and 「Type II」. For Type I vibrations、directions of motions of all nodes are all in parallel with the plain expanded by X-axis(along the moving direction of the train) and Z-axis(along the direction of gravity). The mechanism of this type of vibration can be attributed to the wave-guide effects of 「Track+Slab+Girder」. For Type II vibrations、directions of motions of all nodes are all vertical to the plain expanded by X-axis and Z-axis. The central mechanism of this type of vibrations is the eccentricity of track for the moving loads.
Concluding all the analysis here in、it is discovered that the three factors most critical for the dynamic responses of elevated viaduct and surrounding soils are (1) structural type、(2) train speed、and (3) supporting type of rail-track system.
|
|---|