|
碩士論文公告區 |
||
| 年度： | 92 | |
| 姓名： | 李佳龍(Jia-Lung Li) | |
| 論文題目(中)： | 敲擊所得表面波振幅之衰減率檢測混凝土表面老劣化程度之初步研究 | |
| 論文題目(英)： | Evaluate Surface Condition of Aged Concrete using Amplitude Decaying Rate of Surface Wave Produced by an Impact | |
| 摘要(中)： | ||
| 混凝土表面由於風化中性化以及乾濕循環等效應容易產生微細裂縫造成表面劣化的問題，本研究欲以量測混凝土表面波(雷利波)振幅的衰減率為指標，來評估混凝土表層微細裂縫深度範圍。實驗變數包括改變敲擊元尺寸及接收器距離對檢測的影響。研究是以理論、數值分析及實驗三種方法進行。首先在理論方面推導出半無限域彈性體在不同敲擊接觸時間及材料性質時表面波振幅關係式之理論解，可推導出在混凝土表面未受損時，同ㄧ次敲擊、不同敲擊源—接收器距離所得之表面波振幅比之理論比值，此比值與敲擊之鋼珠接觸時間及混凝土波速有關。在數值及實驗方面，製作混凝土模型及試體，利用不同之鋼珠接觸時間均驗證出在未損壞之砂漿及混凝土試體之敲擊回音試驗結果與理論值非常接近，證明可利用理論解之比值為標準，在比值大於理論比值時，代表混凝土表面裂縫散射表面波傳能量，使表面波衰減率增加。 研究之第二階段於混凝土試體表面上，以人工於表面40公分長度範圍切割間距一公分之多重的均佈表面裂縫以及不規則裂縫，以初步模擬混凝土老劣化所造成之裂縫，並於此範圍施作敲擊試驗。表面裂縫深度由0.25公分變化至2公分，以建立表面不同深度範圍與表面波振幅衰減率之關係。由規則及不規則裂縫的實驗結果得知，在裂縫深度0.75cm以前表面波振幅比與深度走勢是呈線性上升的趨勢，但在裂縫深度大於1.0cm以後由於切割後之混凝土條因敲擊產生共振現象造成表面波振幅比無法呈線性上升趨勢，因此裂縫深度大於1.0cm以後則無法使用此法估計混凝土表面老劣化程度，但本研究實驗結果可利用於檢測粗糙表面，實驗結果其平均誤差在15%以內，初步證明可利用本研究結果估計表面粗糙程度。 |
||
| 摘要(英)： | ||
| Because of the effect of weathering, neutrality as well as dry wet cycling, very small cracks on surface of concrete can easily be produced and cause surface deterioration. This study aims at measuring the amplitude decaying rate of surface wave (Rayleigh wave) as the index for quantitatively evaluating depth of the very small cracking on surface of concrete. The test variables include the effects of changing the size of impactor and distance between impactor and receiver. The study is preceded by the ways of theoretical analysis, numerical analysis and experiments. First, for semi-infinite elastic body the theoretical relations among amplitude of surface waves, the duration of the impact and material properties were solved. The theoretical ratio between the amplitudes of two R-waves recorded from receivers at certain designed distance is calculated. It was found the ratio is varied with the impact-duration and P-wave speed. In numerical analysis and experiment, the ratio of R-wave amplitude is very close to theoretical solution for the numerical model and for both undamaged concrete and mortar specimens. Thus, the ratio solved in theory can be used as a standard for undamaged concrete. When the ratio of experiment is larger than the theoretical one, it represents the cracks scatters propagation energy of surface wave and increases the decaying rate of surface wave. The second stage of the research is studying the effect of multiple cut-slots on surface of concrete specimens to the impact responses. The slots are used to preliminarily simulate the cracking condition of aged concrete. With the range of 40 cm in length, some of the slots are uniform distributed with 1 cm intervals and the others are cut irregularly. Cracking depth is varied from 0.25 cm to 2 cm for establishing the relation between the surface cracking depth and amplitude decaying rate of surface wave. It was found in the experimental results, for the depth of cracks less than or equal to 0.75cm, the decaying rate of surface wave is linearly increase with crack depth. However, for the depth of cracks larger than 1.0cm, the decaying rate of surface wave is not linearly increase with the crack depth because a resonant vibration of the concrete slots were triggered by the impact. Thus, when the depth of cracks is larger than 1.0cm, it is unable to use the method to estimate the surface condition of aged concrete. The test method can be applied for measuring the coarse surface condition. The experimental results show that using the surface wave amplitude to predict the depth of the dip on the surface, the error for average depth of the dip is less than 15%. |
||
| 檔案： | 沒有相關檔案 | |
| 相關連結： | http://ethesys.lib.cyut.edu.tw/ETD-db/ETD-search-c/view_etd?URN=etd-0809104-032032 | |