Fire Resistance of L-shaped Columns Subjected to Different Fire Exposure Cases

摘要

The fire resistance of the columns with L-shaped cross section is lower than that of the columns with rectangular cross section for the former has thinner sectional thickness and larger surface area exposed to fire.Analyses were performed using a numerical program RCSSCF based on the conjugate beam method to study the influence of several parameters, such as axial load ratio,effective length,sectional dimension,load eccentricity ratio, reinforcement ratio and load angle, on the fire resistance of L-shaped columns subjected to the ISO834 standard fire with typical fire exposure cases.20736 columns were selected for fire response analyses.Different axial load ratios, effective lengths, sectional dimensions, load eccentricity ratios, reinforcement ratios,load angles and fire exposure cases were considered in the analyses. Based on the simulation results, a practical calculation method is proposed for the fire resistance of the columns with L-shaped cross section subjected to three typical fire exposure cases. The simulation results indicate that: (a) reducing the axial load ratio is an effective measure to improve the fire resistance of the columns with L-shaped cross section subjected to typical fire exposure cases; (b) the fire resistance of the columns with L-shaped cross section subjected to typical fire exposure cases decreases linearly with the increasing of effective length, whereas increases linearly with the increasing of sectional thickness for the same value of sectional height/sectional thickness; (c) the fire resistance of the columns with L-shaped cross section subjected to typical fire exposures decreases significandy with the increasing of load eccentricity ratio on the whole; and (d) the influence of load angle on the fire resistance of the columns with L-shaped cross section subjected to typical fire exposure cases is significant and complex.