AISC 341韌性銲接組合箱型鋼柱新寬厚比規定研究

Abstract

本研究主要延續 Tedjasukmana(2024)與 Chou and Chen(2020)之研究，探討矩形銲接箱型鋼柱在中軸力與高軸力作用下之耐震行為，並與先前針對正方形銲接箱型鋼柱之實驗結果進行比較，進一步分析翼板與腹板寬厚比變化對鋼柱耐震性能之影響。試驗結果顯示，翼板與腹板之寬厚比均對構件行為具顯著影響，且兩者間存在交互作用；在承受相同軸力條件下，較大的翼板或腹板寬厚比會導致局部挫屈提早發生，進而造成彎矩強度較快遞減與韌性下降，整體耐震行為亦隨之惡化。 Chou and Chen(2020)針對六支採用高強度鋼材(SM570MC)之銲接箱型鋼柱進行反覆側推試驗，探討不同寬厚比、軸力比與載重歷時(AISC反覆載重歷時與近斷層載重歷時)對構件耐震性能之影響，試體之翼板寬厚比範圍為 b/t =11、12、14、16 與20。試驗結果指出，AISC 341 所採用之反覆載重歷時比近斷層載重歷時嚴格許多。Tedjasukmana(2024)則延續此研究，擴大寬厚比範圍至24至36，並分別施加高軸力(0.4Pya)與低軸力(0.2Pya)進行實驗，同時整合過往針對正方形箱型鋼柱之試驗資料，透過迴歸分析提出適用於美國與台灣鋼構規範之建議寬厚比規定，試驗結果顯示現行AISC 341-22對寬厚比之限制過於保守。 然而，Tedjasukmana(2024)所建立之實驗資料庫僅涵蓋正方形銲接箱型鋼柱，為使資料庫更完整，本研究新增六組矩形鋼柱試體之實驗資料，並透過有限元素模擬以擴充資料量，最終建構包含78組鋼柱之完整資料庫，進行迴歸分析並提出修正後適用於正方形與矩形箱型鋼柱之AISC 341高等與中等韌性構件寬厚比建議規定，期能為未來美國與台灣鋼構規範之修訂提供參考依據。

This study builds upon the research conducted by Tedjasukmana (2024) and Chou and Chen (2020), focusing on the seismic behavior of rectangular welded box columns under moderate and high axial loads. The test results are compared with previous experiments on square welded box columns to further investigate the influence of flange and web width-to-thickness ratios on the seismic performance of steel columns. The results indicate that both flange and web b/t ratios significantly affect the structural behavior, with clear interactive effects between the two. Under the same axial load condition, a larger flange or web b/t ratio leads to earlier local buckling, resulting in faster moment strength degradation, reduced ductility, and an overall deterioration in seismic performance. Chou and Chen (2020) conducted cyclic lateral loading tests on six welded box columns made of high-strength steel (SM570MC), examining the effects of different b/t ratios, axial load ratios, and loading histories (AISC cyclic loading protocol and near-fault loading protocol) on seismic performance. The flange b/t ratios of the specimens ranged from 11, 12, 14, 16, to 20. Their results showed that the cyclic loading protocol adopted by AISC 341 is significantly more stringent than the near-fault loading protocol.Tedjasukmana (2024) extended this study by increasing the b/t range to 24–36 and testing under high (0.4Pya) and low (0.2 Pya) axial loads. By integrating previous data on square box columns, a regression analysis was conducted to propose recommended b/t limits suitable for both U.S. and Taiwanese steel design codes. The results revealed that the current AISC 341-22 b/t limits are overly conservative. However, the database developed by Tedjasukmana (2024) only covered square welded box columns. To enhance the completeness of the database, this study adds experimental data from six new rectangular box column specimens and supplements the dataset with finite element simulations. Ultimately, a comprehensive database of 78 steel column cases is established, from which regression analysis is performed to propose revised width-to-thickness limits applicable to both square and rectangular box columns for highly and moderately ductile members per AISC 341. The proposed limits aim to serve as a reference for future revisions of steel design codes in the U.S. and Taiwan.