- 學位論文
混凝土用新型螺紋植筋錨栓動靜態之性能評定
Concrete Use New Type Rebar Screw Anchor Assessment under Static and Seismic Loads
摘要
新型螺紋植筋錨栓，屬於後置式螺絲型錨栓，此螺紋植筋錨栓主要含二部份構件，一端為螺紋錨栓，另一端為與錨栓同尺寸鋼筋，在採用磨擦焊接技術連接為一金屬構件，可採用混凝土鑽尾，於混凝土先預鑽植筋鑽孔後，再以適當施工工具將此新型螺紋植筋錨栓植入現有混凝土，達成後續施工結構物與現有混凝土結構物連結之功效。然土木營建工程結構物之生命週期都很長，且混凝土錨固件連結之荷載均很大，一但失效會引起重大之工安事件，因此歐洲與美洲地區均會要求土木營建工程使用之錨固件，需提供完整評定技術資料。 然我國仍未建立適當錨固件評定制度，本論文研究將以新型螺紋植筋錨栓為例，採用歐盟EOTA EAD 330232及美洲ACI 355.2錨固件評定準則，考量我國位於環太平洋地震帶之因素，針對此新型螺紋植筋錨栓，植入無開裂與開裂低強度(20.6 MPa)與我國工程常採用較高強度(34.3 MPa)之混凝土，執行部分動靜態拉力之試驗及特性評定，並詳細探討此範圍之美洲ACI與歐盟EOTA錨固件評定準則之差異性，以利評估此錨栓是否也具備化學錨栓之結構補強功能。由初步分析結果顯示，EOTA EAD 330232規範計算之特性強度值較ACI 355.2來的保守，並期許本論文試驗結果與建議，可供我國機械螺紋錨栓相關設計規範與評定準則建立之參考。 本研究先執行參考性評估試驗，研究試驗新型螺紋植筋錨栓於植入之埋入深度為201 mm (13d)，在其螺牙段之有效埋入深度為150.5 mm，鋼筋段為#5鋼筋(直徑15.9 mm)，螺紋植筋鋼筋段採用抗張強度為420 MPa之#5鋼筋，混凝土試驗構件標稱抗壓強度包括植入無開裂與開裂低強度之C20/25 (20.6 MPa)混凝土及高強度之C35/43 (34.3 MPa)混凝土。執行動靜態拉力試驗特性評定，經試驗結果顯示，新型螺紋植筋錨栓於C20/25混凝土正規化拉破壞特性抗張強度，採用ACI及EOTA評估準則分析結果，於無開裂混凝土強度分別為82.073 kN 與76.614 kN，而於開裂混凝土分別為54.782 kN 與45.980 kN，如無束制抗張試驗分析結果，兩者皆於EOTA之分析較ACI為保守。另新型螺紋植筋錨栓於C35/43混凝土正規化拉破壞特性抗張強度，採用ACI及EOTA評估準則分析結果，於無開裂混凝土強度分別為113.349 kN與96.365 kN，而於開裂混凝土分別為65.404 kN與50.702 kN，如無束制抗張試驗分析結果，兩者皆於EOTA之分析較ACI為保守。綜合上述，當低強度C20/25混凝土產生裂紋時，錨栓之抗張能力將下降為非裂紋之混凝土約為60~70 %，於高強度C35/43混凝土產生裂紋時，錨栓之抗張能力將下降為非裂紋之混凝土約為55~60 %。 並根據ACI規範計算此螺紋錨栓有效力k-value，以低強度C20/25混凝土之無開裂與開裂條件下，分析k-value分別為9.8與6.7。以高強度C35/43混凝土之無開裂與開裂條件下，k-value分別為10.5與6.1。於無開裂條件下混凝土變化率較穩定，兩者不同強度混凝土皆接近符合規範要求值，而開裂條件下則皆勉強符合規範要求值，仍須執行更多組試驗確定其特性值。 經完成參考性試驗項目，進而執行ACI 355.2 表4.1b第9項開裂混凝土週期性動態可靠性試驗，以#5新型機械式螺紋植筋錨栓一系列C20/25開裂混凝土無束制抗張試驗，結果顯示201 mm(13d)埋入深度，8筆試驗中發生6次為混凝土拉破破壞加拔出破壞及2次鋼材斷裂，採用ACI355.2評估準則分析結果顯示#5新型機械式螺紋植筋錨栓拉出k值為6.7，接近符合規範要求；另#5新型機械式螺紋植筋於C20/25混凝土正規化拉出破壞特性抗張強度，採用ACI與EOTA評估準則分析結果分別為55.644 kN與39.5864 kN，綜合比較此項開裂混凝土無束制抗張試驗分析結果顯示，EOTA之分析較ACI為保守。 綜合比較分析，ACI 355.2表4.1b參考性第3項試驗與第9項開裂混凝土週期性動態可靠性試驗之結果，於錨栓類別之鑑定以開裂C20/25混凝土，執行參考性與可靠性試驗之結果，以F5%特性強度值分別為65.686 kN及56.549 kN，再採用ACI 355.2第十章-鑑定錨栓等級之分析，帶入公式 Nb,r/Nb,o = 可靠性/參考性 = 56.549/65.686 = 0.861 > 0.8，結果顯示，此種錨栓植於C20/25開裂混凝土，其F5%特性強度比值可達0.861，即可靠性之動態試驗在不利條件下可達參考性試驗80%以上之錨栓承載力，鑑定此錨栓達Anchor category No.1。
並列摘要
The new type rebar screw anchor belongs to the post-installed screw-type anchor bolts. It consists of two main components: one end is the threaded anchor bolt, and the other end is a steel bar of the same size as the anchor bolt. These two components are connected as a single metal component using friction welding technology. The new type rebar screw anchor can be used for drilling into concrete by first pre-drilling rebar holes in the concrete and then inserting the anchor bolt into the existing concrete using appropriate construction tools. This achieves the effect of connecting the subsequent construction structure to the existing concrete structure. However, civil engineering construction structures have long life cycles, and the loads on concrete anchorage connections are significant. If these connections fail, it can lead to serious construction safety incidents. Therefore, both Europe and America require comprehensive technical evaluation data for anchor bolts used in civil engineering construction. However, in our country, an appropriate anchor firmware evaluation system has not yet been established. This research will take the new type rebar screw anchor as an example and adopt the European Technical Approval (EOTA) EAD 330232 and the American Concrete Institute (ACI) 355.2 criteria for anchor firmware evaluation. Considering our country's location in the Pacific Ring of Fire seismic zone, this study focuses on the new type rebar screw anchor implanted in both non-cracked and cracked low-strength (20.6 MPa) and higher-strength (34.3 MPa) concrete, conducting partial dynamic and static tensile tests and characteristic evaluations. The research will also thoroughly investigate the differences between the ACI and EOTA anchor firmware evaluation criteria within this scope, in order to assess whether this anchor can serve as a structural reinforcement function similar to chemical anchors.Preliminary analysis results indicate that the characteristic strength values calculated according to EOTA EAD 330232 are more conservative than those of ACI 355.2. It is hoped that the experimental results and recommendations of this thesis can provide valuable references for the establishment of relevant design specifications and evaluation criteria for mechanical threaded anchor bolts in our country. This study first conducted reference assessment experiments on the new type rebar screw anchor to investigate its embedment depth at 201 mm (13d), with an effective embedment depth of 150.5 mm in the threaded section. The steel reinforcement used was #5 rebar with a diameter of 15.9 mm, and the threaded rebar section adopted a tensile strength of 420 MPa for #5 rebar. The nominal compressive strength of the concrete test specimens included non-cracked and cracked low-strength C20/25 (20.6 MPa) concrete, as well as high-strength C35/43 (34.3 MPa) concrete.The execution of static and dynamic tensile tests revealed the normalized tensile failure characteristics of the new type rebar screw anchor in C20/25 concrete. According to the assessment criteria of ACI and EOTA, the results showed an ultimate tensile strength of 82.073 kN and 76.614 kN in non-cracked concrete and 54.782 kN and 45.980 kN in cracked concrete, respectively. Without any limitations from tensile tests, both analyses using EOTA were more conservative than those using ACI.Additionally, in C35/43 concrete, the normalized tensile failure characteristics of the new type rebar screw anchor were analyzed based on the criteria of ACI and EOTA. The results indicated an ultimate tensile strength of 113.349 kN and 96.365 kN in non-cracked concrete and 65.404 kN and 50.702 kN in cracked concrete, respectively. Similar to the C20/25 concrete analysis, both EOTA analyses were more conservative than the ACI analyses when no limitations from tensile tests were applied.In summary, when low-strength C20/25 concrete develops cracks, the tensile capacity of the anchor will decrease to approximately 60-70% of that in non-cracked concrete. In the case of high-strength C35/43 concrete, the tensile capacity of the anchor will decrease to approximately 55-60% of that in non-cracked concrete. Based on the ACI (American Concrete Institute) regulations, the effective k-values for the threaded anchor bolts were calculated. The k-values were analyzed under no-cracking and cracking conditions for low-strength C20/25 concrete, with k-values of 9.8 and 6.7, respectively. For high-strength C35/43 concrete, the k-values were 10.5 and 6.1 under no-cracking and cracking conditions, respectively. It was observed that the concrete variation was relatively stable under the no-cracking condition, and both concrete types with different strengths were close to meeting the specified requirements. However, under the cracking condition, they only marginally met the specified requirements, and further testing is necessary to confirm their characteristic values. After completing the reference experimental program, the periodic dynamic reliability test of cracked concrete specified in ACI 355.2 Table 4.1b, item 9, was carried out using a series of C20/25 cracked concrete unconfined tension tests with #5 new mechanical threaded rebar anchors. The results showed that at a embedment depth of 201 mm (13d), out of 8 tests, 6 resulted in concrete pullout failure and 2 in steel material fracture. The analysis using ACI 355.2 criteria indicated that the pullout capacity (k-value) of the #5 new mechanical threaded rebar anchors was 6.7, which is close to meeting the specified requirements. On the other hand, the normalized tensile pullout characteristic strength of the #5 new mechanical threaded rebar in C20/25 concrete, analyzed using both ACI and EOTA criteria, resulted in values of 55.644 kN and 39.5864 kN, respectively. Comparing the analysis results of the unconfined tension test on cracked concrete, it can be concluded that the EOTA analysis is more conservative than the ACI analysis. Comparative analysis of results from ACI 355.2 Table 4.1b, reference item 3 (reference test) and item 9 (periodic dynamic reliability test of cracked concrete), for anchor category identification on cracked C20/25 concrete, yielded the following outcomes. The characteristic strength values F5% obtained from the reference test and dynamic reliability test were 65.686 kN and 56.549 kN, respectively. Using ACI 355.2 Chapter 10 - Anchor Category Identification analysis, with the formula Nb,r/Nb,o = Reliability/Reference = 56.549/65.686 = 0.861 > 0.8, it is evident that the anchor embedded in the cracked C20/25 concrete achieves a characteristic strength ratio of 0.861. This indicates that the dynamic test reliability under unfavorable conditions can achieve over 80% of the anchor's load-carrying capacity observed in the reference test. Therefore, the identified anchor category is No.1.