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標題: | 橋梁結構之健康診斷:受沖刷效應之影響 In Situ Structural Health Monitoring for Bridges Under Ambient Stimulus : Effect of Scouring |
作者: | Fong-Ming Wu 吳豐名 |
指導教授: | 羅俊雄(Chin-Hsiung Loh) |
關鍵字: | 橋樑沖刷,短時傅立葉變換,Wigner-Ville Distribution,Novelty Index,相關係數分析, Bridge scouring,Short Time Fourier Transform,Wigner-Ville Distribution,Novelty Index,Correlation coefficient, |
出版年 : | 2011 |
學位: | 碩士 |
摘要: | 在台灣每當到颱風季節時許多座橋梁因為強烈的暴風雨而倒塌。這些橋梁的倒塌其主要原因可能是橋梁受沖刷作用使橋柱沉陷並使橋梁承載能力降低與破壞橋梁基礎。由於缺乏橋樑監測系統以及沖刷監測技術,比較難在橋梁倒塌(損害)發生之前做提早預警避免災難發生。
我們認為橋梁結構受沖刷作用的過程,橋梁的基礎邊界會受到改變而且其結構的動力行為(特性)可能會因為上述行為發生改變。在本文中於水工實驗場進行橋梁基礎沖刷的試驗。在實驗監測的過程中將重點放在沖刷深度變化與橋梁受沖刷作用結構的特性之間的關係。量測結構動力反應(震動訊號)將被應用於不同的結構特徵分析技術。(1)短時傅立葉變換(STFT)是比較直接的方法看結構特徵隨時間變化,(2)小波封包轉換將訊號分解並排列重建再以Hilbert 振福表示,(3) Wigner-Ville Distribution (WVD) 結合奇異譜分析可以看出頻率隨時間的變化, (4)遞迴隨機子空間識別也同樣用來做數據監測,(5) Novelty Index 分析能將損害程度以量化的形式來表達,(6)相關係數分析比較不同監測點並找出可能損害位置,(7)CVAC能夠在結構發生損害之前看出徵兆。發展出一套結構健康診斷工具將其應用於現地橋梁量測。 In Taiwan during the typhoon season there were several bridges were collapse due to heavy storm. The major reason for these collapses of bridges is due to the bridge scouring which may induce the settlement of bridge piers, reduce the bridge bearing capacity and damaged the bridge foundation. Because lack of bridge monitoring system as well as the scouring monitoring techniques, it is impossible to send an early warning message before the collapse of bridge so as to prevent the disaster happened. It is believed that structure subject to the scoring process the boundary condition of the bridge-foundation system is changing and the dynamic characteristics of the bridge structure may be modified due to this change. In this study experiments on bridge foundation scouring is conducted in hydraulic lab. During the tests monitoring will focus on the scour-depth variation in relating to the dynamic features of the bridge structure during scouring process. Different feature extraction techniques are applied to the vibration measurements of the structural responses. (1) The STFT (Short Time Fourier Transform) is the most direct method to identify the time-varying system feature. (2) WPT decomposes the signal to many components after arrange and reconstruct every components express by Hilbert amplitude. (3) The combination of moving window singular spectrum analysis (SSA) with the Wigner-Ville Distribution (WVD) is used to identify the time-varying system dominant frequencies. (4) The recursive stochastic subspace identification (RSSI) is also used on the monitoring data. (5) Novelty Index analysis is implemented to quantify the damage severity. (6) Correlation coefficient compares with different sensor and locate the damage. (7) The CVAC also can see the structural feature before damage occurred. Application of the developed structural health monitoring tools on the field data of bridge vibration subject to ambient stimulus is examined. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/47918 |
全文授權: | 有償授權 |
顯示於系所單位: | 土木工程學系 |
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