鋼筋混凝土梁柱組合體火害行為研究

Abstract

在與加拿大國家防火實驗室有關高性能混凝土實尺寸柱高溫加載之抗火能力試驗合作計畫後，發現混凝土實尺寸柱在高溫再加上偏心載重之抗火能力，呈現大幅度的降低。在實際情形下，樑柱組合體的行為因會受到梁的束制，其行為又未必與偏心載重相同。台灣位處環太平洋地震帶上，幾乎所有建築物的結構設計都是由地震力產生的水平力所控制，因此在評估建築物在承受火災後，到底還剩下多少強度，其能承受之水平力的能力，便是評估建築物能否經由修復補強的重要指標。 試驗結果顯示出柱體內部的溫度與外部溫度有很大的差異，大尺寸柱子的耐火能力絕對比小尺寸大很多。如果柱子承受彎矩，由於在保護層破裂後，鋼筋直接曝露在高溫下，使其抗拉能力降低，因此柱子的抗火能力急速降低。使用偏心載重的高溫高壓試驗並無法完全模擬真正結構物受火害行為。柱子承受火害的破壞模式會因為彎矩大小有所不同，彎矩不大時破壞發生於柱子的接頭附近，彎矩增大後破壞模式轉移成為梁破壞。在僅受火害三小時的情況下，試體抵抗水平力的殘餘能力降低並不會很大。

The results from the joint research with NRC Canada found that the fire resistance of column was reduced significantly due to eccentric loading. This research will clarify the difference between column with eccentric loading and beam-column assembly in fire resistance. The design of building in Taiwan area is controlled by the presence of seismic force. The residual horizontal force after suffering fire damage is major index for the safety estimation of building. The results from experiment showed that : Concrete is good insulation material for heat and size effect is important. Explosion of concrete cover cause steel exposing to heat directly and reduce the fire resistance significantly.The failure mode is quite difference between column with eccentric loading and beam-column assembly.The increase of moment transfers the failure mode from column to beam. The capability to resist horizontal force after exposing fire damage for 3 hours is reduced not very much.