高墩柱橋樑懸臂工法拱度控制研究

Abstract

懸臂工法運用於橋梁工程上已是很成熟工法之一，由於其具有結構上跨徑長之特性且具自動化效率，因此在受地形地物之障礙影響時，如跨越山谷、既有公路和鐵道時該工法即具備施工上之優點，使得此工法在國內橋梁建造上日漸廣泛應用。 然而場鑄懸臂工法施工過程中之預拱值控制，是相當重要之一環。 若相鄰兩墩柱在施工過程中兩側拱度差異過大時，將無法在相接時順利閉合，屆時將額外施加外力強制閉合，如此強制閉合將引致額外應力於結構上，恐對結構安全上恐有疑慮；其次各節塊拱度控制不好時其完成面為達設計高程時，必須加舖AC將增加自重，或刨除已完成之混凝土過高面，這些都將造成橋體結構上之損傷影響其耐久性。因此場鑄懸臂工法在預拱值管控上關係到施工成功與否之重要課題。 本文拱度發展趨勢分析，採用最小二乘法並以直線線性迴歸方式，來預測低墩柱之拱度發展趨勢，經施工完成閉合後達到符合精度要求(跨度1/4000)之橋面結構體品質，進而應用該線性迴歸方式在高墩柱施工時之控制，使其在閉合後仍可符合該精度要求，以證明該方式是可提供施工單位在懸臂工法上拱度控制預測之參考公式使用。

Cantilever method is one of the proven techniques applied to bridge construction. Due to its long span on structure and high effeciency in automation, this methods owns unique advantages when construction is affected by obstacles of topography, such as spanning valleys and existing roads and railways. Therefore this method has been widely used in domestic bridge constructions today. During the condution of the cast-in-place cantilever method, camber precontrol is a big part of the construction. If two adjacent pier studs share large disparity on camber values, then they may not be joint when connecting two sides. On that occasion, they shall be connected by compulsory means, which may cause extra stress on the structure and bring risks on structure safety. Moreover, when various segments under poor controlling, a layer of AC, which will increase the self-weight, shall be added; or the exorbitant parts on completed concrete surface shall be reduced in order to meet the designated elevation. All these measures may cause damages on bridge structure and affect its persistence. Therefore, when conducitng cast-in-place cantilever method, camber precontrol is the improtant matter relating to the success of construction or not. In this study, based on the analysis of the camber development trend, we use least square method and liner regression method to make predication on the camber development trend of low pier stud. When the quality of completed bridge construction has met with accuracy requirement (with span of 1/4000), we will apply the liner regression method in construction of high pier stud to make this construction meetwith accuracy requirement as well. Based on the results, we try to prove this method can provide references to construction units on camber prediction and controlling when conducting cantilever method.