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碩士論文公告區 |
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| 年度： | 92 | |
| 姓名： | 李憲裕(Hsien-Yu Li) | |
| 論文題目(中)： | 以應力波速衰減評估混凝土表面老劣化程度之初步研究 | |
| 論文題目(英)： | Preliminary Study on Evaluation of the Surface Damaging Degree of Aged Concrete by Measuring Stress Wave Speed Formation | |
| 摘要(中)： | ||
| 本研究針對核設施巨積混凝土結構元件開發一系統性的檢測流程及分析方法，使混凝土表面由於風化中性化以及乾濕循環等效應產生微細裂縫造成表面劣化的問題，以敲擊回音法量測表面縱波與雷利波波速的損失率及抗壓強度，作為老劣化程度的判定指標。研究由數值及實驗的方法進行，製作混凝土模型及試體其表面以人工方式均佈切割不同深度之裂縫群；此外亦量測以人工海水進行乾濕循環加速老劣化試體之波速及抗壓強度。於老劣化試體波速量測表面劣化關係方面，加速劣化圓柱試體由頻域量測之P波波速與混凝土強度呈正比關係，時域方面則與強度較無關聯。在梁試體方面P波及R波波速與強度間也無明顯關係。在表面切割人工裂縫群方面，雙接收器與可感測時間原點之儀器配置下量測其波速，於數值模擬及實驗得知裂縫深度在0.5cm之前波速損失隨裂縫深度變大但在其後波速損失率較不穩定。從數值模擬均佈裂縫波形圖中發現當裂縫深度為1cm、1.5cm及2cm時敲擊會引發裂縫部分混凝土明顯共振效應，而利用懸臂梁之共振理論推導出頻率與裂縫深度平方成反比的關係，計算數值模擬及實驗結果中得知相關係數(R2)接近1，因此若於現地檢測時有類似梳形裂縫時有機會由裂縫間距及其共振頻率反推裂縫深度。 | ||
| 摘要(英)： | ||
| In this study, a systemic test procedures and analysis methods for evaluating degree of deterioration of mass concrete nuclear facilities caused by weathering, neutral effect and dry-wet circulation are developed. Surface longitudinal and Rayleigh waver speed measured by impact-echo method and compressive strength are used as indexes. Numerical and experimental studies are used. Models and specimens of concrete plate containing evenly distributed surface cracks with various depths were constructed to simulate fine cracks produced on concrete surface while aging. In addition, P-wave speed and compressive strength were measured for concrete cylindrical and beam specimens cured in circulated artificial sea water and oven-dry environments for speeding the aging process. For the accelerating degraded cylindrical specimens, the P-wave speed evaluated in frequency domain was closely proportionally related to the corresponding compressive strength. The P-wave speed measured in time domain has less correlation with the compressive strength. For beam specimens, there is no obvious relation between P-wave or R-wave speed to the compressive strength. For specimens with artificial surface cracks, P-wave and R-wave speeds were measured by two kinds of instrumental setup- namely dual receivers, and one recordable impactor with one receiver. Both numerical and experimental results show the P-wave and R-wave speed decrease with the depth of cracks up to 0.5 cm. For the cases larger than 0.5 cm, the speed and crack-depth have no correlation. It was also found in the numerical simulation that, for crack depths 1, 1.5 and 2 cm, the impact can generate resonant vibration in the sliced concrete. Using the resonant theory for column clamped at base, it can be found that the resonant frequency is inversely proportional to the square of crack depth. The relation was testified in both numerical and experimental results with correlation coefficient close to 1. Thus, it is possible to evaluate the depth of comb-shape multiple cracks using the distance between cracks and the corresponding measured resonant frequency. | ||
| 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-0824104-104925 | |