後置式化學錨栓在低強度混凝土中之錨定行為

Abstract

植筋工程經常於於建築物補強中應用，補強工程之種類繁多，於翼牆補強以及剪力牆補強等工法中，植筋工程更是被廣泛運用。藉由對既有建築物結構進行植筋，進而將補強增設之結構體與既有建築構件相連接，以期發展出良好的結構耐震行為。國家地震中心於台灣校舍補強中發現老舊校舍結構物常有混凝土強度偏低的問題，平均混凝土強度大約為17MPa，因此探討錨栓在低強度混凝土中的錨定行為以及其適用性便成為本研究之課題。 錨栓可依其施工時機分為預埋式錨栓以及後置式錨栓兩種。預埋式錨栓為混凝土進行澆置前便完成安裝，適用於新建結構物；後置式錨栓為混凝土固化後進行錨栓安裝，於工程上具有許多應用方式。後置式錨栓於補強時可依其需要以及施工性選擇埋設孔位，對於新增耐震構件至現有結構體較具機動性及經濟性，於是本研究於錨栓之選擇上採用後置式化學錨栓作為試驗之用。 本研究規劃在混凝土強度分別為5MPa、10MPa、15MPa中，根據Hilti固定技術手冊以及NCREE校舍耐震補強植筋參考圖說之植筋深度建議，進行一系列的單向植筋拉拔測試，共計105組。實驗結果顯示， 對Hilti固定技術手冊建議之植筋深度，應注意其允許抗拉強度之規定；NCREE校舍耐震補強植筋參考圖說之植筋深度則可以予以縮減為65%即可滿足設計需求。

In order to increase seismic capability of structural system, retrofit techniques are usually applied. Traditional RC retrofit methods include adding RC shear wall, wing wall and RC jacketing. In addition to connect new structural members to old structural members anchor bolts (bar implant) are used. From the investigation results by NCREE, we can find that concrete strength of old school buildings is pretty low due to poor structural system and quality. Therefore, the behavior of post-installed anchors in low strength concrete is very important. Anchor system can be categorized into two kinds. Cast-in anchor is installed before placing concrete and post-installed anchor is installed in hardened concrete. Therefore, post-installed anchor is suitable in retrofitting structures. Low strength concrete specimens were designed for rebar-implanting. Through pulling out embedded steel bars from hardened concrete, the failure modes of embedded steel bars are investigated. The influence of the depth of steel bars, concrete strength and detail of specimens is analyzed. Test results indicate that Hilti’s suggestion embedment should be carefully used in accordance with it allowable tensile forces. In addition, NCREE’s suggestion embedment is too conservative we can reduce its length to 65%.