含混凝土防火層鋼結構梁柱接頭之受撓行為

鋼材機械性質受高溫的影響很大，因此鋼結構房屋需要有適當的防火措施，防止火災發生時建築物過早倒塌。有些鋼結構建築物以混凝土作為防火材，並配置縱向及橫向輔助鋼筋，且設計時不計入混凝土及鋼筋可能提供之強度，工程實務上稱此為SC結構。本文以5組大尺寸梁－柱子結構試體之反復載重試驗，探討SC梁結構細部對韌性、強度及裂縫發展之影響。試驗結果顯示：（1）H型鋼梁翼板施作韌性切削對SC梁之撓曲韌性有顯著的幫助，SC梁之塑性轉角容量皆達3% rad以上，符合耐震所需；（2）對梁塑性鉸區之翼板與混凝土間設置握裹隔離裝置，可以提升梁塑性轉角容量約16%，但梁柱交界面處之裂縫寬度在彈性範圍達到9mm，在試驗結束時達39mm，明顯偏大；（3）雖然翼板與混凝土間之握裹隔離裝置可以提升梁塑性轉角容量，但是裂縫寬度過大，且未設置握裹隔離裝置之試體仍然擁有耐震所需之塑性轉角容量，因此設置握裹隔離裝置的必要性低；（4）雖然H型鋼梁與混凝土間未配置剪力釘，但是SC梁中之H型鋼梁與混凝土基本上可發展出完全合成之彎矩強度；（5）縱向輔助鋼筋延伸至鋼箱型柱面，若採用90˚彎鉤錨定，會於柱混凝土面產生額外的裂縫，因此縱向輔助鋼筋延伸至鋼箱型柱面處直接截斷即可，不需採用彎鉤錨定；（6）縱向輔助鋼筋在壓力側可發展出87%之降伏應力，根據本試驗之經驗，梁塑性鉸區輔助箍筋之間距限制在10倍縱向輔助鋼筋直徑以內，可以有效避免縱向輔助鋼筋受壓挫屈，此經驗可供工程實務參考。

關鍵字

SC結構； SC梁；鋼結構梁柱接頭；鋼骨鋼筋混凝土；混凝土防火層

並列摘要

The mechanical properties of steel are greatly affected by high temperature; thus, steel structure buildings need to have appropriate fire protection measures to prevent premature collapse of buildings in the event of fire. In some cases, steel structure buildings use concrete as fireproofing material. Although longitudinal and transverse steel bars are also provided as auxiliary reinforcements, but the strength that can be contributed by these steel bars is not considered in the strength calculation during design process. In engineering practice, this kind of structure is known as SC structure. In this study, five beam-column sub-assemblage was tested under cyclic loading to investigate the influence of SC beam structural details on beam strength, ductility, and crack development. The test results show that the use of reduced beam section beam-to-column connection detailing is necessary since it can significantly increase the flexural ductility of the SC beams. The SC beams can develop the full composite action even though without using any shear stud. The use of isolation layer between beam flange and concrete in plastic hinge region is not necessary since it only slightly increase the plastic rotation capacity of the SC beams but causes larger crack in the concrete at the beam-to-column interface. The auxiliary longitudinal rebar is provided up to the face of box column and the use of 90° hooks are not recommended since it will cause additional cracks. The local buckling of the auxiliary longitudinal rebar can be effectively avoided when the distance between the rebar is less than ten times of its diameter.