鋼骨箱型柱內橫隔板電熱熔渣銲接之有限元素分析

Abstract

鋼骨箱型柱具有雙強軸的優點，其內橫隔板電熱熔渣銲接為組合箱型柱必要的一道銲接程序，該銲道緊鄰梁與柱交接面，細微的銲接瑕疵可能導致梁柱接頭於發展出韌性行為前之脆性破壞。本文採用有限元素分析，以裂縫尖端開口位移、應力三軸度與破裂指數行為指標討論電熱熔渣銲接對於梁柱接頭行為之影響。有限元素分析模型分析結果顯示，側墊板間隙、電熱熔渣銲接之熔入半徑與鋼梁相對於電熱熔渣銲之偏心等參數並非影響梁柱接頭行為之關鍵因素；而電熱熔渣銲道偏心若使側墊板間隙尖端距離橫隔板邊緣越近，將使得裂縫尖端開口位移越大而不利於梁柱接頭之行為。美國北嶺地震後的改良型式梁柱接頭，如梁翼切削、肋板與擴翼型式接頭，均能有效改善電熱熔渣銲接之行為指標。

Electro-slag welding for diaphragms is the necessary welding procedure to build-up a steel box column which can resist bending in both axes of the cross section. Electro-slag welding (ESW) locates nearby the beam-to-column interface, and minor defect in the ESW could result in a brittle failure before plastic behavior is developed in the connection. Finite element analysis was conducted to study the effects of the ESW on the behavior of the connection through the investigation of performance indices, such as crack tip opening displacement (CTOD), stress triaxility, and rupture index. The results of the finite element analysis show that the parameters of the slit of the backing bars, melted radius of the ESW, and the eccentricity of the beam flange with respect to the ESW have little effect on connection behavior. However, a smaller distance between slit tip and the edge of the diaphragm due to the eccentricity of the ESW results in a larger CTOD that could be detrimental to connection behavior. The improved connections proposed after the Northridge earthquake, e.g., reduced beam section, rib-reinforced and widened flange connections, can be beneficial for enhancing the performance indices of the ESW.