الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
A finite element model for concrete-filled steel box columns subjected to fire loads has been used to evaluate the failure temperature of these columns. The effect of concrete strength, steel tube thickness, load level and springs at the upper end of the columns were considered. The study investigated the failure temperature, deformations, reactions and stress in the columns’ section. The effects of each of axial, lateral and rotational springs were studied independently to form an overall view about the effect of each one of them on the failure temperature. Each one of them was studied in a separate parametric study. Also, the effect of concrete strength and tube thickness were investigated individually with the change of axial spring stiffness values. Finally, models combining these springs were studied to get the combined effect of these springs. Using the results from these models, charts and formulae to estimate the failure temperature of concrete-filled steel box columns subjected to fire loads were proposed for the purpose of design. The first formula is used to estimate the failure temperature of free column knowing its tube thickness and load level. Then, the second formula is used to modify this value using the axial spring stiffness ratio. After that, the third formula modifies the latter value using the lateral spring stiffness ratio. Finally, the last formula gives the final temperature using the rotational spring stiffness ratio.