鋼筋混凝土樑受火害時之溫度分佈與殘餘強度分析

Analysis of Temperature Distribution and Residual Stress of Reinforced Concrete Beam after a Fire

鋼筋混凝土結構物在受火害後，鋼筋及混凝土材料因各位置承受不同溫度而變為非均質，因為其力學性質主要為最高溫度之函數，因此欲分析了解火災後結構物之安全性，必須先清楚各構件在火災時之溫度分佈。本研究以熱傳遞原理模擬鋼筋混凝土複合材料矩形樑斷面受不同形式火災時之溫度分佈，探討鋼筋混凝土樑遭受一面、側邊與底部二面、兩側邊，以及三面均受火害情況下樑內部的溫度分佈，同時進一步分析斷面不同部位之殘餘強度。結果顯示鋼筋混凝土樑的內部溫度非常不均勻，樑側邊的火勢會減低樑上半部混凝土的抗壓強度，而樑下方的火勢會嚴重影響鋼筋的降伏強度。透過溫度分佈之模擬，再加上鋼筋與混凝土受火害高溫之力學影響分析，結果將有助於對火災後建築物之安全有進一步之了解。

The fact that different parts of the cross-section of a beam are exposedto different temperatures during a building fire makes the stress distributionin such structures a nontrivial problem. This study employs the Finite Dif- ferent Method to model the various temperature distributions of reinforcedconcrete beams after fire exposure. Then, the present investigations calculatethe residual stress on beam-sections, while considering the influence ofhigh temperature on the reinforced steel and concrete. The informationcould be helpful to understand the extent of potential damage to the structureof a building after a fire.