以藍姆波群波速之頻散曲線偵測混凝土品質與混凝土表面劣化深度

The Preliminary Study of Using the Dispersive Velocities of Lame Waves to Detect the Quality of Concrete Plate and Depth of Surface Deterioration

魏信怡(Shin-Yi Wei)

指導教授 ： 鄭家齊

朝陽科技大學/理工學院/營建工程系/碩士(2014年)

摘要

研究中主要以應力波原理為基礎的檢測方法來檢測混凝土板老劣化狀況，將以頻率-波慢譜呈現之板波模態(Lamb wave modes)評估混凝土板損壞狀況、並以波長-頻率圖推估混凝土板劣化深度。
利用單一敲擊源及單一接收器的反應位移波形，取得試驗之頻率-相位波速頻散曲線圖，再與DISPERSE程式得到之理論解做比較分析。研究中以單層混凝土板(牆)、純混凝土板、純水泥漿+混凝土雙層複合板及表面火害試體，進行試驗及分析比較。單層混凝土板(牆)試驗結果顯示，較長之敲接距離及較大之敲擊源，所激發出之波慢譜與理論解A0板波波慢相符，但只能分辨波長為0.2 m以上之波速，而淺層混凝土波速需縮短敲接間距才可取得。
純水泥漿+混凝土雙層複合板試驗結果顯示，弱層厚度0.06 m及0.1 m時，實驗結果顯示波長為劣化層厚度的1.5倍以內其波速約為定值，且接近弱層水泥漿體P波波速的一半。
表面火害試體試驗結果顯示，不同於水泥漿-混凝土雙層複合板試體高頻的能量可經由水泥漿體傳遞，而有明顯的低波速訊號，由於短波長的高頻波被表面裂縫阻擋，短波長的波速並不明顯，波速成穩定值處的最小波長大約為劣化厚度的1.5倍。

關鍵字

劣化深度 ； 混凝土

並列摘要

The study is based on stress wave method to detect deterioration of concrete slab. The dispersion curves in frequency-slowness spectrum generated by Lamb wave modes of the slab are used for the assessment. The depth of the deterioration of the concrete slab is estimated by the wavelength - frequency diagram.
Using the displacement waveforms obtained by one impactor and one receiver, the group velocity dispersion curves, and then with the theory DISPERSE program get the solution to do comparative analysis.
Research to single concrete slab (wall), pure concrete slabs, and concrete surface layer composite panels and fire damage specimens, were tested and analyzed. Single concrete slab (wall) test results showed that the longer the distance, and then choosing a large source of percussion, the slowness spectrum would be more consistent with the theory of slow wave solution A0 mode. The group velocity can only be obtained for the wave with wavelength larger than 0.2 m. The velocity of shorter wavelength required shorten impactor-receiver distance.
The experimental results corresponding to the cement-concrete layered composite panel showed that group velocity is approximately constant for the wave with the wavelength of less than 1.5 times the thickness of the deterioration and closes to half of the P-wave velocity of the weak layer of cement paste for the cases with 0.06 m and 0.1 m thick weak layer.
For the specimen with surface damaged by fire, the results show that, the short wave-length waves are blocked by the surface cracks and is not obvious in the wavelength-velocity graph, unlike cement layered specimen where high-frequency energy can pass through the cement paste and induce signal of low velocity. The minimum wavelength of the wave with constant velocity is about 1.5 times the thickness of the deterioration.

並列關鍵字

Depth of Deterioration ； Concrete

參考文獻

6. 倪勝火，「表面波譜分析法（SASW）之分析原理與應用」，地工技術，第86期，第5-18頁，2001。

25. 林進興、蘇百加，「表面波譜分析法（SASW）之實務與應用」，地工技術，第86期，第19-28頁，2001。

2. Roberts, T.M. and Haji-Kazemi, H., ‘Theoretical study of the behavior of reinforced concrete beams strengthened by externally bonded steel plates’, Proc. Instn.Civil Engrs, Part 2, 87, 1989, 39-55.

3. Swamy, R.N., Jones, R., and Bloxham, J.W., ‘Structural behaviour of reinforced concrete beams strengthened by epoxy-bonded steel plates’, The Structural Engineer, 65A (2), 1987.

4. Jones, R., Swamy, R. N., Charif, A., ‘Plate separation and anchorage of reinforced concrete beams strengthened by epoxy-bonded steel plates’, The Structural Engineer, 66 (5), 1988.