以敲擊反應進行預力鋼鍵長度評估之初步研究

Preliminary Study on the Length Prediction of Prestressed Strands by Impact Responses

李雅玲(Ya-Ling Li)

指導教授 ： 余志鵬

朝陽科技大學/理工學院/營建工程系/碩士(2010年)

摘要

地錨為一般常見輔助邊坡穩定之設施，由於看不見完成錨碇後之預力鋼鍵的真正情況，通常地錨施工後之實際錨碇長度無法得知。然而地錨實際施工總長度可以掌握，倘能在不破壞結構體的情況下，經由特定的非破壞檢測法評估鋼鍵自由段的長度，便可藉此判斷錨碇長度，間接評估錨碇結構的安全性。
本研究利用1-D構件振動理論解，提出一開根號公式進行鋼鍵長度反算，並與繩索理論進行適用性比較。經實驗分析後可知，二種理論公式均可用於評估鋼鍵長度，但開根號公式在未知軸力及邊界條件之情況下仍可對鋼鍵長度進行評估，而繩索理論公式僅能在軸力為已知時，且僅由第一振態進行評估。此外，將開根號公式初步應用於鐵絲與預力電桿之實際案例中，開根號公式反算結果雖仍有差異，但顯示其具潛在可行性。

關鍵字

非破壞檢測技術 ； 地錨 ； 預力鋼鍵 ； 敲擊反應

並列摘要

Ground anchor is a common facility used in strengthening slope stability. The anchored length normally remains unknown after erection since the anchor is buried and can not be inspected. However, the total length of an anchor strand is normally a controlled value, it is then possible to recover the anchorage length by evaluating the unbonded segment through certain non-destructive testing techniques. With the anchorage information being recovered, the anchor strength can thus be assessed accordingly.
This study proposed a back-computing formula, derived from 1-D member theory, for the prediction of strand length from natural frequencies. Such formula was compared with the well-known cable formula in the prediction of lengths of prestressed strands. The proposed formula is superior to the cable formula since the former can be applied without knowing the level of axial forces and boundary conditions while the later requires axial force being a given parameter. The preliminary applications of the proposed formula to the determination of lengths of very thin steel wires and prestressed concrete poles indicate that the proposed formula can be a potentially useful tool yet further modifications in the analysis process are still in demand.

並列關鍵字

non-destructive testing techniques ； Ground anchor ； prestressed strands ； impact responses

參考文獻

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【17】 司裕仁，『預力斜吊鋼索之動力特性研究』，碩士論文，國立臺灣大學土木工程學研究所，2003年。

【2】 C. P. Yu, C. C. Cheng, S. T. Hsu, and J. Lai, “Deetermination Of Unbonded Length For Strands Of Ground Anchors Using Impact Responses Of 1-D Member Theories”, EASEC-11, 2008。

【11】 Federation Internationale de la Precontrainte (FIP) Corrosion and corrosion Protection of Prestressed Ground Anchorages, 1986.

【14】 陳佑嘉，『受軸力樑桿件之基本振動特性研究』，碩士論文，朝陽科技大學營建工程系，2009年。