本文以有限元素方法，計算鋼管混凝土實心柱，在高溫下受壓力時的潛變行為。潛變模型為時間的指數函數。混凝土與鋼材均假設為等向均質線熱黏彈性材料，其界面為熱完美及力學完美界面。運用Abaqus有限元素軟體，在不同溫度下，求解此一熱傳方程式與黏彈方程式偶合的力學問題。對耐火鋼材而言，雖然圓形比方形斷面有較高的抗火能力，但方形比圓形斷面有較佳的抗潛變能力。此外，本文亦觀察到潛變導致的挫屈現象。統合來說，耐火鋼大幅的提升鋼管混凝土實心柱的抗高溫能力，在極高溫時，混凝土的脆性破壞為主要的破壞機制。

Concrete-filling in hollow structural section (HSS) steel columns has many beneficial effects and is becoming more popular in high-rise and industrial buildings. At ambient temperature,the load-bearing capacity of these composite columns is significantly increased. Thus, it is possible to reduce cross-sectional dimensions, which results in reduced construction costs and enhanced usable space in buildings. In addition, the advantageous thermal properties of concrete lead to increased fire resistance of these composite columns. Therefore additional external fire protection for the steel might be superfluous. However, the fire resistance of concrete-filled steel tubular columns should be research carefully to predict the behavior of these columns exposed to fire.
By using a finite element method (FEM) program is Abaqus/CAE Standard, this thesis has investigated the fire resistance of the axially loaded square and circular concrete-filled steel tube columns when exposed to elevated temperatures are 400 C, 500 C, and 600 C. The comparisons of the square and circular CFST columns of different sizes and different steel tube thicknesses, different steel type have shown that for columns having the same concrete and steel materials, although the circular column has slightly higher fire resistance than the square column, but the square columns have higher creep resistance than circular columns. The simulation results show that all of columns can stand the temperature of 400 C over than 10 hours without failure. The results also show that fire resistance steel improved the fire resistance of CFST columns significantly. However, at high temperature, concrete is crushed to bring about collapse of CFST columns. The failure of CFST columns is very suddenly and very difficult to predict.

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