FIRE RESISTANCE OF END CONSTRAINED COLUMNS WITH SPECIAL-SHAPED CROSS SECTION

The existing of adjoining members may influence the fire resistance of the heated columns with special-shaped cross section. In order to investigate this influence, this paper proposes a numerical model for end constrained columns with special-shaped cross section at elevated temperature. Using 2-dimensional thermal analysis rectangular elements and 3-dimensional beam elements, a full-process analytical program was developed for the behavior analysis of end constrained columns with special-shaped cross section subjected to fire, and the effects of axial constraint and rotational constraint on the fire resistance are analyzed. The results show: 1) axial constraint will introduce significant additional axial forces in concrete columns, which are approximately 65% of the axial forces at room temperature. 2) rotational constraint can significantly increase the fire resistance of columns with special-shaped cross section. 3) the fire resistance of columns without rotational restraint decreases significantly with an increasing of load eccentricity ratio, but the load eccentricity ratio has little influence on the fire resistance of columns with rotational constraint.