受車載影響樑型結構之系統識別及損傷偵測:利用隨機子空間與小波包轉換法

Abstract

本研究的目的在於利系統識別方法:協方差隨機子空間識別法(Covariance-driven stochastic subspace identification, SSI-COV)與小波包轉換法(Wavelet packet transform)識別橋梁受車橋互制系統並考慮隨機路面粗糙度之影響。本研究第一部分利用有限元素數值模擬方法(Finite element method)，模擬兩跨連續橋梁受到移動車載引致互制外力影響並考慮路面粗糙度。從不同量測點的訊號反應，利用SSI-COV識別橋梁的頻率。為了排除互制效果(tuned effect)在穩態圖(Stability diagram)上出現的僞系統極點(spurious pole)的現象，採用小波包轉換法重建可能為僞系統極點的訊號並觀察不同量測點訊號的相位差。第二部分是將上述SSI-COV方法應用於關渡大橋(Guan-Du bridge)的參數識別，並探討不同量測時間所繪製的穩態圖分析。此外，損傷分析方法應用於樑型結構上包括: (1) Subspace、Null-space damage index (DIn,DIs,DI) (2) Hilbert Amplitude Assurance Correlation (3) Change in flexibility。 透過模擬兩種破壞形式包括: (1) 橋梁元素(element)勁度折減(2) 橋梁支承勁度折減。上述之損傷分析均應用於橋梁的損害評估上。

Application of system identification technique, known as Covariance-driven stochastic subspace identification (SSI-COV), cooperated with Wavelet packet transform (WPT), to identify the dynamic characteristics of bridge under bridge-vehicle interaction with considering random road surface roughness. In the first portion of this study, numerical simulation of a two-span continuous bridge using finite element model is presented with the consideration of bridge-vehicle interaction and road roughness. From the response signal collected in different locations, SSI-COV was applied to identify the bridge vibration frequencies. In order to eliminate spurious poles due to the tuned effect of bridge and vehicle vibration phenomenon, wavelet packet transform was used to reconstruct signals of possible spurious modes and observed the phase difference among the measurements. The second part of this study is using the proposed SSI-COV method to identify the dynamic characteristics of a bridge in its operating condition: Guan-du Bridge. Discussion on the stability diagram from different measurement time is discussed. In addition, damage detection of bridge-like structure are also proposed: (1) Subspace-Null space damage indices (DIn、DIs、DI), (2) Hilbert Amplitude Assurance Correlation, and (3) Change in system flexibility. Through numerical simulation of damage scenarios: (1) Stiffness reduction in one of the bridge element, (2) Stiffness reduction on the bridge bearing system, the proposed damage indices were applied for damage assessment of the bridge.