預力損失對混凝土電桿強度影響之初步研究

近年由於地球的氣候暖化，引起全球氣候的異常，間接造成未來的颱風強度有越來越大的趨勢，嚴重威脅到架空線路之安全性。在製作電桿過程中，都會在混凝土內部之鋼筋上預先施加拉應力增加其抗拉強度，以抵抗側向風力等自然因素所對其造成之損害。本研究藉由程式模擬驗證傳統預應力計算之合理性，探討電桿內部鋼腱不同之預力損失方式；如單根預力損失、整體預力損失，以及混凝土內部鋼筋預力損失與強度之關係。研究之進行首先驗證以溫度效應模擬預應力效應的合宜性，其次以三維有限元素模型探討電桿斷面應力非均勻分佈情況之現象，參數研究發現電桿斷面最臨界之張應力狀態較之平均張應力狀態的差異性可達20%至30%左右，故以簡單線桿理論估計之張應力計算值具有潛在不保守性。研究中針對電桿同時受側向風壓作用之研究，發現典型9米電桿最大張應力發生位置大致落在距地面線處1.5米至2米處之區域，顯示該位置為檢討現有電桿設計方式時之重點探討區域。

關鍵字

有限元素法；電桿；預應力損失

並列摘要

Due to global warming, the intensity of typhoons tends to be stronger and thus seriously threatens the safety of power lines. To enhance capacity in resisting wind loads, prestressing technique has been applied to the fabrication of pole structures. As a result, this study aims to investigate the effect of prestress losses on the behavior of pole structures and the validity of formulas in the traditional analysis procedure. In this study, prestressing effect was simulated by temperature effect and the feasibility was confirmed. The realistic stress distribution of the cross section was then studied with 3-dimenional FEM models. Parametric studies showed that the difference between predicted tensile stresses by the FEM model and the uniform assumption can be as large as 20% or so. Therefore, the traditional simplified theory regarding line members may potentially result in non-conservative predictions. For case studies of 9m poles with wind loads acting on simultaneously, it was found that the critical region for tensile stresses is located within 1.5 to 2 meters from ground line. Modifications to design details at such region would then be of particular interests.

並列關鍵字

Concrete Electric Pole ； Prestress Losses ； ANSYS

參考文獻

【12】德泰水泥製品股份有限公司，9.0MB型預力電桿設計圖，圖號：TT-90-1，2005年2月。

【6】Bangash, M. Y. H. , Concrete and Concrete Structures: Numerical Modeling and Applications, Elsevier Science Publishers Ltd., London, England,（1989）。

【1】徐安、張曉萍，「環形鋼筋混凝土電線桿縱裂問題的探討」，漯河職業技術學院。