以軸力梁理論提昇預力鋼纜傳統評估公式實用性之研究

Assessment of Prestressed Cables Using Improved Cable Formulas Based on Axially Loaded Beam Model

巫文勝(Wen-Sheng Wu)

指導教授 ： 余志鵬

朝陽科技大學/理工學院/營建工程系/碩士(2014年)

摘要

本研究旨在改良傳統繩索理論公式之應用方式，傳統繩索公式未考量撓曲剛度與邊界條件等因素，因此其正確性不佳。本文以軸力梁理論推導出兩種折減方式，分別對應於簡支梁與雙邊固定端梁模型。利用適當折減因子值，繩索理論公式可獲得符合鋼纜實際軸力之估算值。由於傳統的計算公式需事先知道鋼鍵撓曲剛度及長度等材料性質，因此，本文提出藉由任意兩頻率便能取得撓曲剛度之表示式，使得撓曲剛度為非已知的情況下也能由任意兩個振態頻率估算軸力之方法。此外，透過任意兩個頻率以數學方式進行重整，亦能獲得長度之替代計算式。最後，本文探討正弦函數假設下多點公式長度反算之機制，此類公式透過兩點或三點接收器之反應，利用頻率振幅值，推算鋼鍵長度。由數值模擬與實驗進行比較之單點、兩點及三點公式的實用性，可發現單點公式極具潛力，但多點公式之正確性顯然不佳。

關鍵字

鋼纜非破壞檢監測 ； 振動長度 ； 預力鋼索 ； 繩索張力

並列摘要

This work aims at improving the applicability of the traditional cable equations used in the cable assessment task. In a traditional analysis scheme, predictions are less reliable since effects due to boundary conditions and flexural rigidity are neglected. Based on the axially loaded beam, this work investigated two types of models, namely simply supported beam and fixed beam. By applying these beam models, the accuracy of predicted cable forces and lengths using only one sensor can be greatly improved. Moreover, both rigidity and length information are explicitly required in the traditional way of analysis, while such data can be implicitly replaced by additional mode frequencies in the proposed method. In this work, the theoretical background of the proposed formulas is first introduced and summarized, followed by a comprehensive parametric study carried out using an FEM program. The feasibility of the formulas are next verified and illustrated by lab experiments on two sets of 7-wired strand specimens. Finally, another approach for length recovery in which presumable sinusoidal shape and multiple sensors are used is also explored and compared to the proposed method. It was found that the proposed method gives promising results and more reliable length predictions over the ones based on multiple sensors.

並列關鍵字

Mode shape ； Mode frequency ； Cable Force ； Cable length

參考文獻

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【2】智能型儀器系統(Intelligent Instrument System)