利用空間位移訊號進行結構局部�系統損壞評估

Application of Spatial Displacement Measurement on Damage Assessment from both Local and Global Structural System

李其航(Chi-Hang Li)

指導教授 ： 羅俊雄

國立臺灣大學/工學院/土木工程學研究所/碩士(2012年)

https://doi.org/10.6342/NTU.2012.00330

摘要

現今結構物健康監測技術多經由普通接觸式量測計（如：加速度規、速度規…等）裝設於結構物量取反應訊號進行分析判斷。為獲取結構細部反應資訊而大量安裝儀器的情況下，此種量測法將會有佈線繁雜以及裝設位置選項過少等問題產生。然而受惠於光學科技之進步，此問題可有效解決。光學量測方法是將待量測位置標示上一可經由影像辨識之目標點，藉由攝影裝置觀測目標移動情況進行三維動態分析。只要目標位於裝置監控範圍內，此方法將能進行大規模位置點計算。
本研究重點在探討此光學量測位移訊號應用於結構系統識別及破壞診斷的適用性。分析方法分為兩大類。第一類是整體系統識別方法，對於1.只需結構反應的斜方差型隨機子空間識別 (Covariance driven Stochastic Subspace Identification, SSI-COV)，和2.需系統輸入輸出資訊的子空間識別 (Subspace Identification, SI) 作探討，應用光學多維訊號進行自然頻率與阻尼比分析。再來是研究3.主成分分析 (Principal component analysis, PCA) 應用此訊號進行結構模態識別。第二類是局部系統評估，在將光學量測點網格化為數個單元後，應用幾何分析概念進行4.奇異譜分析 (Singular spectral analysis, SSA) 獲取單元之主要動態做進一步幾何處理。另外應用5.連續小波轉換 (Continuous Wavelet Transform, CWT) 分析訊號不連續性，對破裂做動時間點進行判斷。單元也可由6.有限元素法 (Finite element method, FEM) 計算其應變動態行為。本研究將會針對單層雙垮鋼筋混凝土桁架的振動台實驗進行實際應用。此實驗使用集成式光學量測儀器DMM (Dynamic Measuring Machine) 量測中間柱三維位移訊號。分析結果顯示應用此種空間位移訊號，整體系統識別方法可有效的獲取結構物資訊，並對結構變化進行描述；網格化之動態行為分析也能為結構局部破壞提供重要資訊。

關鍵字

結構健康監測 ； 空間位移 ； 訊號處理 ； 奇異譜分析 ； 有限元素

並列摘要

In this research, the capability of advance spatial displacement measurement for structural health monitoring (SHM) is studied. The method for obtaining this kind of data is different from regular measuring system. It utilizes the optical processing technique to calculate the specific particles’ locations (called targets) within an image. While taking image and compute the locations over time, the dynamic motion can be estimated. This research employed the three dimensional displacement from optical sensors to identify system and perform damage assessment.
The applied signal analysis methodologies can separate into two categories, global system identification and local element motion detection. For global system, two subspace methods including 1.covariance-driven stochastic subspace identification (SSI-COV) and 2.recursive subspace identification (RSI) are examined. They can obtain the system natural frequency and damping ratio based on different condition. The other method is 3.principal component analysis (PCA), which the system normal modes can be briefly calculated while the measured locations are distributed along the system. For local motion, we can discretize the targets into a set of local elements. These elements motion is detect by 4.singular spectral analysis (SSA), 5.continuous wavelet transform (CWT), and 6.finite element method (FEM). The extracted information is used to describe the structural local properties and detect the damage occurrence. To examine the applications of these methodologies on real three dimensional displacement data, a shake table test of one-story two-bay RC frame performed in the NCREE is selected. This experiment installed a totally integrated optical measuring system (DMM, by NDI Inc.) on its central column to obtain the displacement. The analysis results show that this kind of data is capable for system identification, and the detection of damage is also feasible. Detail analyzes the discrete elements. The damage location may be obtained.

並列關鍵字

Structural health monitoring ； spatial displacement ； signal processing ； singular spectral analysis ； finite element method

參考文獻

16. Mao, C.-H., Nonlinear System Identification Method for Structural Health Monitoring: Techniques for the Detection of Nonlinear Indicators, in Department of Civil Engineering,2009, National Taiwan University.

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