鋼骨托梁抗彎接頭含梯度漸擴式梁翼板之耐震行為

Abstract

鋼骨托梁式建築由於擁有較佳工廠銲接品質的優勢，因此普遍的被台灣與日本的工程界採用。然而，於1995阪神地震中觀察到此型式之梁柱接頭發生非預期的脆性破壞。本研究之目的為發展新型式之托梁抗彎接頭，改良方式為逐漸擴大一部分之梁翼板使梁之彎矩容量符合耐震彎矩梯度，藉由大範圍之降伏區域提高梁柱接頭的韌性行為。 一系列有限元素參數研究用以探討各設計參數對於梯度擴翼板幾何形狀之影響。數值分析結果顯示，梯度擴翼式接頭可於梁梯度漸擴段展現廣泛的塑性降伏範圍，並將塑性鉸機制移離梁柱交接處。實尺寸梁柱接頭試驗，包括試驗一組傳統托梁式接頭與六組梯度擴翼式接頭，以驗證其耐震性能。試驗結果顯示，傳統托梁式試體於扇形開孔根部之撕裂導致梁翼板之脆性斷裂；而梯度擴翼式試體能發揮層間變位角5% 弧度之行為，並提供穩定的消能效果。根據參數研究與實尺寸梁柱接頭試驗之結果，提出梯度擴翼式梁柱接頭之設計流程。此外，本研究利用非線性的構架側推分析，探討應用此梯度擴翼式接頭之抗彎構架的耐震特性，並與採用傳統未補強式接頭之抗彎構架比較。構架分析結果顯示，採用梯度擴翼式接頭之抗彎構架，具有穩定的非彈性行為及滿意的韌性能力。

With a prospective advantage of better quality control of the shop welding, steel column-tree constructions are widely used in design practice of Taiwan and Japan nowadays. These connections used in the column-tree system are fabricated in the shop by welding short pieces of stub beams to the column. However, brittle fracturing of the column-tree connections was observed during the 1995 Kobe earthquake. The purpose of this study is to develop a new scheme of moment connections for steel column-tree moment-resisting frames. This connection improvement is intended to enhance the ductility of the connection by tapering portions of beam flanges following the seismic moment gradient. A series of the finite element parametric study was conducted to investigate the effect of the taper flange geometry on the connection performance. Numerical analyses revealed that significant yielding spread around the tapered region of the beam and took place away from the column face. Full-scale subassemblage specimens, consisting of a typical pre-Kobe connection and six tapered flange connections, were designed and tested to clarify their seismic performance. Experimental observations demonstrated that the pre-Kobe specimen failed caused by a brittle fracture of the beam flange originated from the toe of the weld access hole, whereas the specimens with the tapered flange connection sustained a sufficient 5% rad story drift angle and resulted in stable energy dissipation. A design procedure of the tapered flange connection, accordingly, is proposed based on the results of the finite element analyses and full-scale connection tests. In addition, pushover analysis of frames with tapered flange connections was carried out. The performance of the tapered flange frames was compared to that of the moment-resisting frames with unreinforced connections. The results of the structural analyses demonstrated that frames with tapered flange connections have stable inelastic performance and satisfied ductility.