中高層建築結構填充型箱型鋼柱之載重比

Abstract

研究旨在探討符合國內耐震設計規範之建築結構於使用性狀態下，填充型箱型鋼柱所承受之軸壓比、彎矩比及載重比分布範圍，並進一步探討兩案例填充式箱型鋼柱軸壓比分布對應之防火時效。軸壓比、彎矩比及載重比分別為柱構件於使用性狀態下所承受之軸向壓力、彎矩以及軸壓與彎矩共同作用與其分別之極限強度比值。 本研究以結構分析軟體建立兩棟國內中高層建築結構模型，為含填充型箱型鋼柱之十二層樓以及二十一層樓鋼骨鋼筋混凝土(Steel Reinforced Concrete, SRC)建築物。柱構件依平面位置可區分為角柱、長邊柱、短邊柱、內柱。分析結果顯示，兩案例於使用性狀態下，填充型箱型鋼柱之軸壓比皆不超過0.3，且隨柱構件所在樓層數增加而減小；內柱與長邊柱之軸壓比一般高於短邊柱以及角柱。相關研究成果顯示填充型合成柱構件之耐火性能主要受軸向載重之影響，彎矩之影響甚小，故於忽略柱彎矩之影響時，填充型箱型鋼柱構件於無使用防火被覆情況下，皆可滿足建築技術規則要求之一小時防火時效。然而，僅有短邊柱可於不使用防火被覆情況下滿足兩小時防火時效規定。影響填充型箱型鋼柱構件彎矩比分布之主要原因為建築結構平面跨度大小。將軸壓比與彎矩比相加所得之載重比最大於十二層樓案例不超過0.4，二十一層樓案例不超過0.3。兩案例之分析顯示，國內之建築結構因須符合耐震設計規範要求，填充型箱型鋼柱構件於使用性狀態下所承受之需求強度與其極限強度之比值偏低。

This study aims to investigate the axial load ratio, moment ratio, and load ratio of concrete-filled steel box columns in service conditions while the columns were designed to satisfy domestic seismic design specifications. Moreover, the fire resistance of the concrete-filled steel box columns was also studied based on their load ratios. Axial load ratio, moment ratio, and load ratio were the ratios of service axial compression, service moment, and the interaction of axial compression and moment to column’s ultimate strengths, respectively. With concrete-filled steel box columns, two steel reinforced concrete (SRC) medium- and high-rise buildings, 12- and 21-story, were modeled using commercial structural analysis software. Based on their locations, columns can be classified into corner column, long edge column, short edge column and interior column. Analysis results demonstrated that, in service conditions, all axial load ratios of concrete-filled steel box columns in both buildings were less than 0.3. The higher floor the columns located at, the lower the axial load ratios were. Generally, the axial load ratio of long edge and interior columns were higher than those of short edge and corner columns. Literature showed that the fire resistance of concrete-filled steel box columns mainly influenced by the axial load but not moment. Neglecting the effect of the moment and without fireproofing, the concrete-filled steel box columns can satisfy the one hour fire-rated requirement of Building Technical Regulations. Nevertheless, only short edge columns could achieve the two hours fire-rated requirement. The span of the buildings is the main cause to affect the moment ratio of the concrete-filled steel box columns. The load ratios of concrete-filled steel box columns were not larger than 0.4 in the 12-story building and less than 0.3 in the 21-story building. The analysis of the two buildings indicated that the ratios of service load to ultimate strength of concrete-filled steel box columns are small due to the consideration of seismic design.