機械式螺紋植筋錨栓於非開裂混凝土之基本性能試驗

化學(植筋)錨栓與機械式錨栓廣泛使用於房屋修復 (繕)、補強、改建及新舊混凝土結構物之連結，而目前台灣以化學(植筋)錨栓為主要選用之材料。然而，預鑽孔的清理、植筋膠的混合狀態、混凝土的溼度、養護時的氣溫與時間等重要因素皆影響化學(植筋)錨栓的工程特性。因此，機械式錨栓成為另一替代材料，而過去扭距式膨脹錨栓因有完整的試驗數據與資訊可供設計時用，所以廣泛被採用，但工程師對於該型錨栓之長期抗震能力信心缺乏，故，機械式螺紋錨栓被發明並成為結構物補強之材料。本研究目的為評估新發明的材料：機械式螺紋植筋錨栓，是否能成為另一替代化學(植筋)錨栓之材料。因此，選擇#4、#5化學(植筋)錨栓、國內自行研發之植筋膠及機械式螺紋植筋錨栓於設計強度20.6和34.3 MPa非開裂混凝土中執行抗張及抗剪試驗。化學(植筋)錨栓的埋入深度約為10倍錨栓直徑。除此之外，本研究亦針對機械式螺紋植筋錨栓之熔接處執行熔接處強度試驗。 #4及#5機械式螺紋植筋錨栓熔接處強度皆大於鋼筋破壞強度，而#4及#5化學(植筋)錨栓於20.6和34.3 MPa之混凝土抗張強度分別為85 kN & 86 kN，及103 kN & 117 kN；抗剪強度則分別為57.4 kN & 56.7 kN，及94.8 kN & 92.1 kN。從試驗結果顯示機械式螺紋植筋錨栓抗張強度與抗剪強度隨混凝土強度上升而提升約40至50 %。#4和#5機械式螺紋植筋錨栓在設計強度20.6 MPa之混凝土抗張強度為81.6 kN與121.8 kN，其破壞模式以錨件拔出為主要破壞，並藉由ACI 355.2-07分析公式計算之k值介於9.0至9.3，略小於規範值 (10-13)；然而，#4和#5機械式螺紋植筋錨栓植入設計強度34.3 MPa混凝土時其抗張試驗破壞模式皆屬於鋼筋拉斷，其對應抗張強度分別為91.1 kN與131.2 kN，其對應k值為9.3 至11.7，由上述k值顯示，#4機械式螺紋植筋錨栓於整體設計上仍有改進空間。且機械式螺紋植筋錨栓植入20.6 MPa及34.3 MPa設計強度混凝土時之抗剪破壞模式皆為錨栓剪斷，其抗剪強度由鋼材特性決定。由以上結果顯機械式螺紋植筋錨栓之抗張強度或抗剪強度為大於或等於化學(植筋)錨栓之抗張及抗剪強度。因此#4與#5機械式螺紋植筋錨栓應可成為替代化學(植筋)錨栓應用於混凝土結構之補強及修復之材料。

關鍵字

錨固技術；混凝土修復；後置式錨栓；機械式螺紋植筋錨栓；化學(植筋)錨栓

並列摘要

Chemical bonding gels and mechanical anchor bolts are widely used for remediation, rehabilitation, retrofit, and innovation between the existing and post-construction concrete structures. Currently, chemical bonding anchors are commonly used in local rehabilitation projects. However, the engineering properties of chemical bonding anchors are significantly influenced by several factors, such as cleaning process of the drill hole, mixture condition of bonding gel, moisture condition of concrete, curing temperature and duration. Therefore, mechanical anchor bolts are another alternative for the application of remediation and retrofitting of concrete structures. Torque control expansion anchors are the most popular mechanical expanded anchors that were commonly used in the past. These anchors consist of extensive tests data and technical information as reference for design and construction. However, the strength and durability of these anchors were concern by the engineers during earthquake condition, therefore, screw anchor bolt was invented for concrete structure rehabilitation recently. The objective of this study is to evaluate the engineering properties of this new invented screw rebar anchor whether it is adequate as a replacement product of chemical bond anchor for concrete structure rehabilitation purpose. Therefore, a series of tensile and shear tests of typical chemical bond anchors and the developed rebar anchors were conducted. The test materials included #4 and #5 rebar anchors, a local make chemical bonding gel with #4 and #5 steel rebars, and 20.6 and 34.3 kPa compression strength concrete blocks. Only uncracked concrete was considered in this study. The installation depths of chemical anchors were equivalent to 10 times of rebar diameter. In addition, a series of tensile test was also conducted to evaluate the fusion strength of the rebar anchor product itself. The fusion point strengths of #4 and #5 rebar anchors were found to be greater than that of steel rebar strengths. The tensile strengths of the #4 and #5 chemical anchors for 20.6 MPa and 34.3 MPa concrete were 85 kN & 86 kN, and 103 kN & 117 kN, respectively. The shear strengths of the #4 and #5 chemical anchors for 20.6 MPa and 34.3 MPa concrete were 57.4 kN & 56.7 kN, and 94.8 kN & 92.1 kN. The test results indicated that rebar anchor tensile strengths and shear strengths increased about 40 % to 50 % as the concrete compression strength increased from 20.6 MPa to 34.3 MPa. The average tensile strengths of #4 and #5 rebar anchors installed in 20.6 MPa concrete blocks were 81.6 kN and 121.8 kN, respectively. The primary failure mode was pullout. The average analyzed k values based upon the tensile strengths for the #4 rebar anchors were ranged from 9.0 to 9.3 which were slightly less than the values (10-13) specified by ACI code. It is implied that a minor revision of anchor bolt design may be required. However, the steel breakage failure mode was observed for the tensile tests of 34.3 MPa concrete for both #4 and #5 rebar anchor. The average tensile strengths for #4 and #5 rebar anchor were 91.1 kN and 131.2 kN, respectively. The associated k values were 9.3 and 11.7 which were within ACI code specified range. In addition, steel shear failure modes were observed for the rebar anchors installed in both compression strength concrete blocks. The tensile strengths and shear strengths of the test rebar anchors were equivalent or greater than that associated with the test chemical bond anchors. The test #4 and #5 rebar anchors can be considered as a replacement product of chemical anchor for the rehabilitation of concrete structures.