Analysis of bending moment of restrained RC columns in heating and cooling process

With the help of SAFIR, the bending moment of reinforced concrete (RC) columns in the heating and cooling process is analyzed, and the influences of such parameters as sectional dimension, reinforcement ratio, heating time and rotational restraint stiffness ratio, etc. on the bending moment at the mid-height of restrained concrete column exposed to the ISO834 standard fire with cooling phase are investigated. The results are then compared with those corresponding to the ISO834 standard fire without cooling phase. Moreover, based on the simulation of 192 cases, a practical calculation method for the bending moment at the mid-height of column exposed to fire with cooling phase is proposed. It is thus shown that (1) the enhancement coefficient of the bending moment at the mid-height of axially-restrained column first increases and then gradually decreases till to a constant in the fire with cooling phase, which is quite different from that in the fire without cooling phase; (2) the enhancement coefficient of the bending moment at the mid-height of axially-and-rotationally-restrained column first rapidly decreases and then gradually decreases till to a constant in the fire with or without cooling phase; and (3) the proposed calculation method is of high accuracy, and the correlation coefficient between the calculated results and the simulation ones reaches 0.992.