鋼結構梁柱接頭一般採用RBS(Reduced Beam Section)處理以增進其韌性。但是當鋼梁採用混凝土防火層時，梁柱接頭如何處理方能保有應有之韌性及服務性，為本文研究的重點。透過不同的結構細部配置，並以大型結構試驗的方式來探討其韌性及服務性的表現。本研究總共完成了五組梁-柱子結構試體之反復載重試驗，NR試體梁柱接頭未做任何處理，R1試體採95%及1/2梁深切削，R2-I採90%、2/3梁深切削且在切削處做握裹絕緣處理，R2-C試體90%、2/3梁深切削且增設CAP(Composition Action Plate)，R2-CC試體90%、2/3梁深切削、增設CAP且縱向鋼筋藉由續接器與鋼柱連結。

研究結果顯示：(1)梁柱接頭未處理之NR試體塑性轉角容量僅1.73%，韌性不足；(2)所有採用RBS切削之試體，其塑性轉角容量接近或超過3%；(3)CAP所產生之壓桿，在混凝土未開裂前，能有效分擔鋼骨剪力；(4)縱向鋼筋藉由續接器與鋼柱連結（R2-CC），對試體服務性有明顯幫助；(5)建議含混凝土防火層鋼結構梁柱接頭應採用RBS；(6)為了避免縱向鋼筋90°彎勾錨定於柱面造成柱面破壞，建議縱向鋼筋取消90°彎勾設計並在柱面前截斷。

RBS (Reduced Beam Section) is commonly used for beam-to-column connections of steel structures. However, when concrete cover is used as fire protection layer, the details of the beam-to-column connection should be assessed regarding the ductility and the serviceability of the connection. In this research, 5 sets of beam-column subassemblies were fabricated and tested under cyclic loading to investigate the behavior of the beam-to-column connections with various structural details. NR specimen used untreated beam-to-column connection, R1 specimen used 95% moment capacity and 1/2 beam depth RBS, R2-I specimen used 90% moment capacity and 2/3 beam depth RBS with isolation for bond stress in RBS portion, R2-C specimen used 90% moment capacity and 2/3 beam depth RBS with CAP(Composition Action Plate), and, R2-C used 90% moment capacity and 2/3 beam depth RBS, CAP, and with longitudinal reinforcing bars connected to the box column by coupler.

Test results shows that：(1) beam-to-column connection without RBS possessed only 1.73% of plastic hinge rotation capacity, which is not sufficient for earthquake-resistant structures；(2) Specimens using RBS possessed a plastic hinge rotation capacity of about 3%, which is considered comparable to pure steel beam-to-column connections with RBS；(3) The compression strut induced by CAP provided extra path to transfer shear force；(4) Connecting longitudinal reinforcing bars to box column by coupler can obviously improve the serviceability of the structure; (5) it is suggested that RBS should be used for steel beam-to-column connections with concrete cover as fire protection layer; and (6) It is suggested that longitudinal reinforcing bars should not anchor to column concrete with 90 degree hook, instead, it is suggested to cut the reinforcing bars at the position of column concrete surface.

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