Behavior of Reinforced Concrete Columns with ‘T’-Shaped Cross Section after Exposure to Fire

Abstract

The residual strength of reinforced concrete (RC) columns with ‘T’-shaped cross section after fire are decreased more quickly than those of RC columns with rectangular cross section for the former have thinner sectional thickness and larger surface area. The influence of several main parameters, such as exposure times, effective lengths, sectional dimensions, load eccentricity ratios, reinforcement ratios, load angles and longitudinal reinforcement yield strength on the residual strength of RC columns with ‘T’-shaped cross section after exposure to fire was investigated. A self-developed finite element program CAFIRE was applied in this study. 24300 hypothetical cases of columns after subjected to fire on all sides were selected for residual strength analysis. Different fire exposure times, effective lengths, cross section dimensions, load eccentricity ratios, reinforcement ratios, load angles and longitudinal reinforcement yield strength were considered in the analyses. Based on the simulation results, a practical method was proposed for calculating the residual strength of columns with ‘T’-shaped cross section after subjected to fire on all sides. The simulation results indicate that: (a) the residual strength of columns with ‘T’-shaped cross section decreases linearly with the increase of effective length, but it increases linearly with sectional width, ratio of sectional height to sectional width, and yield strength of longitudinal reinforcement strength; (b) the residual strength of ‘T’-shaped columns decreases markedly for a load eccentricity ratio in the range of 0.0 to 1.0, whereas it varies slightly for a load eccentricity ratio between 1.0 and 3.0.