约束混凝土柱升降温全过程弯矩分析

利用SAFIR程序，开展了约束混凝土柱的升降温全过程弯矩分析。考察了截面边长、配筋率、升温时间、转动约束刚度比等参数对ISO834标准升降温过程作用下约束混凝土柱半高处弯矩的影响规律，并与单调升温时的相应规律进行了对比。通过192种工况的计算分析，建议给出了该类构件半高处弯矩变化系数的实用计算方法。研究结果表明：①升降温过程中，无转动约束柱的半高处弯矩变化系数呈现出先逐渐增大而后缓慢降低并渐趋平缓的变化趋势，明显不同于单调升温时的一直增大现象。②升降温过程中，转动约束柱的半高处弯矩变化系数首先迅速减小继而缓慢降低并渐趋平缓，单调升温时的变化趋势与此基本类似，但后期可能出现变化系数增大的现象。

Analysis of Bending Moment of Restrained RC Columns in Heating and Cooling Process

Using the computer program of SAFIR, the influences of some parameters (i.e., sectional dimension, reinforcement ratio, heating time, and rotational restraint ratio, etc.) on bending moment at the mid-height of restrained concrete column exposed to ISO834 standard fire with cooling phase are analyzed, and compared with those corresponding to ISO834 standard fire without cooling phase. Based on the simulation results of 192 cases, a practical calculation method for bending moment at the mid-height of column subjected to fire with cooling phase is proposed. Simulation results show that: (a) the enhancement coefficient of bending moment at the mid-height of axially restrained column increases first and then drops gradually in fire with cooling phase, this trend is quite different with that in fire without cooling phase; and (b) the enhancement coefficient of bending moment at the mid-height of axially-and-rotationally restrained column decreases rapidly first and then drops gradually in fire with or without cooling phase.