以藍姆波群波速之頻散曲線檢測鋼板補強混凝土結構完整性之初步研究

Preliminary Study on Evaluation of the integrity of RC Structure Strengthened by External Steel Plates using the Dispersion Curves of Lamb Wave Group Velocity

柯盈慈(Ying-tzu Ke)

指導教授 ： 鄭家齊

朝陽科技大學/理工學院/營建工程系/碩士(2010年)

摘要

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，開發的利基是以頻率-時間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表面波分析法取得頻散曲線，利用有限元素分析，以動態有限元素法建立鋼板模型模擬鋼珠敲擊並擷取不同節點的反應位移波形，取得數值解之波慢頻散曲線圖，再與DISPERSE程式所得到之理論解作比較分析。研究中模擬單一純鋼板、兩層複合板(鋼板+混凝土)作分析比較。模擬分析結果顯示，敲擊接觸時間以3μs為最佳選擇，敲擊接收間距最好能達到40.05至50.05 cm，其頻譜圖訊號解析度最佳，可於頻率時間譜圖中顯示與A0、S0及A1理論解相符之高振幅影像。此外，兩層複合板數值模擬影像顯示，當混凝土層存在時，純鋼板反對稱模態A0頻散曲線附近的影像在高頻區域之波慢會較理論解低，而接近S0、A1以及於低頻區域的A0頻散曲線之影像均會消失。下層波速越接近鋼板於低頻位置接近A0頻散曲線之影像會較明顯。

關鍵字

藍姆波 ； 頻散曲線

並列摘要

Concrete structures strengthened by steel plate have been used for more than a decade. As full bonding between the steel and matrix concrete is essential for effectively transmitting loading, infilling must be fully filled inside the gap between steel plate and concrete. The defects which are enclosed inside the steel plate may not be observed by visual observation. Present research is a preliminary study on using the dispersive characteristics of the Lamb wave modes traveling within the steel layer to assess the bonding condition between steel plate and substrates. The advantage of the technique is the capability on investigating large range of the interfacial condition with fast speed. The dispersive curves are obtained by analyzing the surface waves recorded by one receiver and generated by one impact source. In present study, numerical models were constructed to simulate an impact applying on the surface of a steel plate. The spectrogram contains image of the numerical dispersion curves were obtained from the dynamic responses of the receiver. These images were compared with the theoretical solution obtained from a software DISPERSE. The numerical models include steel plate and steel-concrete bi-layered plate. Numerical results show that the most suitable parameters for obtaining the best image are 3 μs for impact-duration, and 40.05 to 50.05 cm for the impact-receiver instance. The high-amplitude images corresponding to A0, S0 and A1 theoretical modal dispersion curves of the steel plate can be found. In addition, numerical images corresponding to steel-concrete composite plate show that the high-amplitude image close to the dispersive curve of fundamental antisymatric mode(A0) of the steel plate becomes lower in slowness. The images of S0, A1 and A0 at lower frequency range cannot be found.

並列關鍵字

Dispersion curves ； Lamb wave

參考文獻

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