英文篇名
THE QUALITY CHECK-UPS OF THE PRESTRESSED ANCHOR AND ITS IMPROVEMENT IN THE ROUTINE ACCEPTANCE TEST
作者
張清秀、王文禮
摘要
台灣近年來隨著經濟之繁榮與需要,建築物地下基礎之開挖規模逐漸增大,地下工程之設計日趨複雜,造成地下結構體之構築與基礎開挖時內部支撐配置愈趨困難,因此,採用地錨背拉支撐工法之可行性則廣泛被考慮。惟台灣工程界鑑於過去少數預力地錨工程失敗之經歷,因此對採用此種施工方法總是持著特別謹慎之態度,其實在國外已有工程採用背拉式地錨施工,開挖深度達地下33公尺深者(歐晉德等,1983),相信只要增進施工時對地錨之品管,加上配合開挖工程進行中周詳之觀測,以檢核地錨之預力強度是否合乎設計之安全標準,地錨背拉式支撐工法之效果在許多深基礎開挖情況下必較內部支撐工法為有效。本文針對地錨之施工品管作概略的介紹,引述有關預力地錨拉力實測之案例,予以整理分析,以期獲得一有效之預力地錨負荷值之檢核與改善方法,使工程人員對地錨之施工品管有進一步的認識,俾能破除心理障礙,樂於接受及採用此一經濟有效的支撐方法,則亦是筆者撰寫本文所樂於期盼獲得的一些成果。
英文摘要
As part of the quality control procedure, all the prestressed earth anchors are to be checked to see if the prestress loads meet the design requirements. This step is usually called acceptance tests for the prestressed earth anchors.
In general the prestress load applied on the prestressed earth anchors is measured by the pressure gage of the hydraulic jack during the acceptance tests. However, due to tendon friction and other operation difficullies, the reading from the pressure gage usually does not correctly reflect the load transferred to the earth anchor. Therefore, load cells are introduced to measure the prestress load and serve as a check to those measured by the pressure gage. Nevertheless, because of the accuracy of the load cell and its measuring apparatus, the incorrect arrangement of the load cells in contact with the anchor plate, or the insufficient stiffness of the anchor plate itself, the accuray of prestress load measurement using load cells remain to be a problem. Three cases of earth anchor acceptance tests are described in this paper. The problems encountered in those cases are discussed and analyzed by the authors. An improved method which can measure the prestress load more precisely is also presented.