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Position: 鄭家齊 > ePortfolio > Project
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1. 以表面波群波波速頻散曲線評估鋼筋混凝土及道路結構剖面勁度/Using the dispersion curve of surface wave group velocity to assess stiffness profiles of reinforced concrete structure and pavement
2015-08 ~ 2018-07

本計畫將以單一敲擊源及單一接收器的方式進行試驗,經短時快速傅立葉轉換以及再分配頻譜求取混凝土結構及道路結構的群波波速頻散曲線,在混凝土表面劣化方面,將參考表面波譜法之反算方法,以表面波所造成之群波波速-波長關係求取沿混凝土厚度的勁度變化剖面,評估劣化深度及沿深度方向E值變化;在混凝土內部瑕疵方面,由於瑕疵將會產生繞射、撓曲振動及基頻外之模態訊號的改變,因此本計畫將發展快速訊號辨識的技術,由複雜的時頻譜轉換成簡易的指標,判定內部瑕疵的種類及尺寸;在道路結構部分,將利用上述評量混凝土結構的方式評判鋪面層之厚度及勁度分布,另外將以拉大敲擊接收間距以及使用重敲擊源的方式,求取道路含路基剖面的表面波群波頻散曲線,並反算分層深度及勁度。本計畫將以軟體自動判別方式,由表面劣化或路面結構的群波時頻譜或波長-波速譜求取分層勁度,以及簡易判別在混凝土內含空洞孔隙試體檢測之實驗時頻譜之不正常訊號,因此不僅單一敲擊及接收器試驗方式可增加檢測速度,檢測結果亦轉化為普通工程師能夠看得懂的物理特徵,此檢測技術發展成熟後可以大範圍快速檢測混凝土結構的問題及道路鋪面分層厚度。

 In this study, test with single impactor and receiver will be conduct on reinforced concrete structure or pavement structure and the spectrogram of group velocities will be obtained via short-time Fourier Transformation and Reassigned method. For the problem of surface degrading of concrete, the inverse methods developed for SASW method will be applied to calculate the stiffness profile from the group-velocity and wavelength relationship of surface waves. For problems with interior voids or cracks, as the inclusions may cause wave refraction, flexural vibration or changes on modal vibrations other than fundamental modes, identification techniques will be developed to transfer the complicated spectrogram into simple indicators for quick assessment of the type and dimension of inclusions. For the pavement structure, the previously mentioned methodology will also be applied to obtain the layering thickness and stiffness. For the instrumental setup of test on pavement, the interval distance between the impactor and receiver will be increased and the heavy impactor will be used to obtain the stiffness profile of pavement and base layers. As the project will develop software to automatically identify the stiffness profile or the simple indicator for abnormal signals, not only the speed of the test can be increased via single impactor and receiver setup. The testing results can be transferred into the physical characteristics that normal engineers can follow. Speedy tests can be performed in large area to detect the problems in RC structure and pavement stratified structure. 

 

2. 以板波群波速時頻譜快速大範圍檢測混凝土板內瑕疵及混凝土後方掏空狀況/文 Fast assessment of internal defects and underneath void for concrete plate using the reassigned spectrogram
2012-08 ~ 2015-10

 本計畫的預期目標為開發一表面波量測技術,以遠距單一敲擊源與接收器的配置快速檢測混凝土結構內部的問題,原本計畫中所述之研究三方向為混凝土板內部瑕疵的探測,混凝土澆置時品質不佳產生蜂窩孔隙或預力套管內部未填滿以及混凝土板下方掏空狀況檢測。在第一年研究數值分析結果顯示,此方法可迅速判別混凝土表面劣化時,劣化深度深度及劣化層波速,因此本計畫再加上快速檢測火害後或離析泌水狀況下混凝土品質的相關研究。

Two types of damages can be categorized for concrete plate like structure: Plate contains voids and delamination or hollow. Voids exist underneath the plate-like structure. In the study, lamb waves generated by applying an impact on the surface are used to evaluate the damage problems. The test is performed with one receiver positioned away from the impact. As different lamb wave modes traveled with different group velocities, spectrogram of the response of the receiver can be obtained by Short-Time Fourier Transformation and reassigned technique. As the technique only requires single impact and single receiver, large range and fast evaluation can be achieved. The project will be carried out in three years. For the first year, the dimensions of the impactors and the interval between the impactor and the receiver to obtain the optimized spectrogram for different plate-thickness would be explored. The characteristic spectrograms of plate containing delaminated cracks with different dimensions will be studied. For the second year, the effect of poor concrete quality, such as voids, honeycombs and unfilled prestressed tube, to the spectrogram would be explored. For the third year, the problem of voids under concrete plate-like structure will be examined. Software which can show the spectrogram real time would be developed also would the guidelines for fast identification of problems for concrete plate-like structure. Three subjects have explored using the finite-element modeling- proper choices for the impact duration and distance between impactor and receiver, the comparison of the spectrograms obtaining from a plate with and without the underlying soil layer and the response for two-layered concrete plate with weak upper layer.             

3. 結構材料性質老劣化之非破壞快速檢測技術開發-子計畫:老劣化鋼板補強混凝土結構快速檢測技術之開發(II)
2010-08 ~ 2011-07
鋼板補強在工程界應用已有十餘年的歷史,在施工作業方面已有完整的步驟流程。鋼板與混凝土完全黏結才能達到複合材料的補強效果,環氧樹脂或無收縮水泥漿必須灌注充滿於其間空隙。然而在補強後大部分之混凝土構件均被包覆於鋼板內部,由結構外表無法觀察到內部環氧樹脂是否注滿混凝土與鋼板之間隙、鋼板是否產生剝離,或內部混凝土是否存在裂縫或病變等問題。本研究將研發以藍姆波群波速之頻散曲線為基礎的檢測方法來檢測鋼板補強結構老劣化狀況,開發的利基是以群波波慢-頻率譜快速評估大範圍的鋼板介面黏結狀況,本研究是以單一接收器與單一敲擊源之位移或速度波形,由Matlab程式作計算,得到數值解短時傅立葉轉換計算之群波波慢頻散曲線圖,再以再分配法求取較精確之群波波慢頻散曲線圖,並與DISPERSE程式得到之理論解作比較分析。最後以複合版之再分配頻譜與單純版的差異性探討以單敲擊源及單接收器所求取之群波慢頻散曲線做鋼板與下方混凝土黏結狀況的可行性。

Structures strengthened by steel plate are popular in Taiwan. As full bonding between the steel and matrix concrete is essential for effectively strengthen the RC structure, the epoxy must be fully filled inside the gap of steel plate and concrete. During the serving lifetime of the steel strengthened structure, the possible defects inside the structures, which can not be observed from its appearance, may be induced by peeling of the steel plate, epoxy partially filling, or corrosion of steel bar inside concrete. The aim of the study is to apply multiple stress-wave-based nondestructive testing methods for evaluating the deterioration of structures strengthened by steel plate. In this study, the larger area of a strengthened structure is examined first by the dispersion curves of the Lamb modes generated in steel plate. The locally defected area is then evaluated by the simulated transfer function obtained from the impact-echo responses. The internal defect of concrete inside the shelled steel plate is evaluated by the SASW method. To achieve the aim of speedy testing, the spectrogram is obtained by single receiver using the short-time Fast Fourier Transform with reassigned technique. The project will be carried out in three years. For the first year, following the 1-year research project conducted on 2008, the feasibility of using single receiver to obtain the spectrogram will be evaluated by the finite-element method. Tests on steel plates with various thicknesses will also be conducted. For the second year, solid concrete plate specimens strengthened by steel plate were constructed for developing the proper testing procedures to obtain correct spectrogram. The effect of unbonded area between steel plate and concrete to the diagram will be studied. For the third year, beam specimens will be constructed. The specimens will be damaged by fire or mechanical loading and strengthened by steel plate. After strengthening, the specimens will be damaged again by four point bending test to create debonding between the steel plate and concrete. The non-destructive testing will be performed at each stage.

 

Keywords: concrete, steel plate, Spectrogram, Lamb wave, impact-echo method, SASW.

4. 敲擊回波檢測對大尺寸鋼筋握裹狀況之檢測評估
2010-07 ~ 2011-03

本案的目的是以敲擊回波檢測技術,評估大尺寸鋼筋握裹狀態改變或局部破壞情況下之混凝土破壞狀況,建立未破壞及破壞時檢測訊號/頻譜之變異特徵的定性比對資料,並提供作為力學實驗結果之對照比較。將利用其委辦計畫所建立之握裹實驗試件及樑,進行非破壞檢測系列試驗,主要檢測方法為敲擊回波法,在部分件上並配合核研所乾點式低頻超音波設備進行B-scan檢測。在握裹實驗試件試驗方面,首先建立#6#10#14#18鋼筋在「固定混凝土保護層厚度條件」下之基本檢測訊號/頻譜,並比較拉拔試驗前、載重至預估破壞強度之40%時及載重至握裹破壞開始發生階段,敲擊回波檢測對應之正規化頻譜差異性;其次在方面,在四點彎曲試驗前、每一次加/卸載循環之卸載期間或最終破壞後(視現場條件決定),進行敲擊回波法之B-scan檢測及主要生成裂縫之深度檢測,B-scan檢測結果做定性之比對。

5. 遠距微波動態位移量測系統於橋梁檢測應用之初步研究
2010-01 ~ 2010-12
檢測與維修橋梁一般分為三個步驟;第一步先進行目視調查以了解各橋梁基本狀況,如發現被掏空、劣化及橋面板損壞等,再進一步作較詳細的鑑定。第二步是以各種儀器進行監測,進一步分析橋梁狀況後,如需要修補,再進行第三步必要的工作,如封橋、修復或補強。國內目前常用之整體監測工具包括在橋梁上安置速度規或加速度規藉由橋體震動來計算橋梁結構共振頻率、阻尼、振形或衝擊係數等,或者以應變計、位移計、光纖光柵、線性位移計等量測橋體的變形,但這些方法均需固定參考點或必須進行數值積分方才能獲得絕對變位且儀器架設較費時,而新近發展之遠距微波動態位移測量儀(IBIS-S)即可使用遠距離以及非接觸之方式,採用靜態或動態模式擷取資料,可即時獲得受測物多點之絕對變位、速度、加速度等相關資訊,擷取之資料可供橋梁系統監測、檢測等多方法使用。

近年來橋梁之安全維護與評估越來越受管理單位重視,然而橋梁安全維護管理所依靠的是定期定點之監測與檢測作業,而本計畫即針對此目標,藉著儀器非接觸式遠距多點檢測特性,進行儀器裝置開發、與檢測流程研發,本計畫預期之成果如下:

(1)           研發出適於遠距微波動態位移量測儀之反射裝置

(2)           開發遠距微波動態位移量測儀應用於橋梁檢測之方法與檢測配置