單肋板補強鋼骨梁柱接頭之耐震行為

Abstract

鋼結構韌性抗彎構架在1990年代中期美國與日本先後發生劇烈地震後，調查發現梁柱接頭韌性不足，影響鋼結構建築之安全性。傳統H型鋼梁接H型鋼柱之梁柱接頭於梁翼板內側扇形開孔處有應力集中現象，再加上此區為銲接熱影響區母材易脆化，故常於此處產生初始裂縫進而造成梁柱接頭破壞。為改善梁翼板扇形開孔之應力集中現象，本研究使用在梁上下翼板中心線上各加銲一塊肋板之單肋板補強型式接頭，藉降低扇形開孔處應力集中現象以增加接頭韌性。製作四組實尺寸試體進行試驗，探討單肋板補強型式梁柱接頭之耐震行為。其中兩組肋板長度較短之試體，韌性行為表現不穩定，肋板末端之梁翼有撕裂之潛在危機。另外兩組長肋板補強型式接頭韌性表現良好，並能滿足國內外規範對於塑性轉角之要求。最後並建議長肋板補強型式接頭之設計流程與施工細部，提供實際工程使用，落實研究成果。

The standard beam-to-column connections used in the steel moment resisting frames showed brittle failure behavior during the 1994 Northridge earthquake. One of the main causes of those connection failure was initiated by the cracking occurred due to the stress concentration at the root of the access hole. This research proposes to use a single vertical rib, which welded to top and bottom flanges of the beam along the centerline of the flange, to eliminate the stress concentration and improve the connection ductility simultaneously. The experiment was conducted to investigate the ultimate moment strength and ductility performance of connection strengthened with a single rib. Four full-scale specimens were fabricated and tested. Experimental results demonstrated that the seismic behavior of the two specimens with the shorter rib were unstable since fracture occurred at the beam flange near the end of the rib. However, the plastic rotation of the other two specimens with longer rib reached 4% and showed significant improvement of the ductility. The design procedure and details of the single rib configuration are also suggested in this investigation.