考虑防屈曲支撑影响的钢筋混凝土框架柱设计方法

针对防屈曲支撑 混凝土框架(RC-BRBF)体系中防屈曲支撑（BRB）对相连柱产生附加变轴力影响，提出了RC框架柱设计方法。该方法首先通过等价轴压比指标获得RC柱设计轴压比限值，保证了一级、二级以及三、四级框架柱极限侧移水平分别达到2.7%、2.4%以及2.1%；然后通过体系延性水平获得柱位移延性指标，保证其延性性能。研究表明，RC柱设计轴压比限值与等价设计轴压比水平、构件受等效重力与地震作用的轴力标准值之比有关；改进后的设计方法能够有效考虑BRB对相连柱附加变轴力影响，并保证了变轴压比下柱的极限侧移水平。算例分析结果表明，该方法通过优化柱截面提高了体系经济性，同时保证体系满足“三水准”设防目标，RC柱设计轴压比限值的设定是合理的。

Design method for columns in reinforced-concreteframes with buckling-restrained braces

An improved design procedure for reinforced-concrete (RC) columns in conjunction with buckling-restrained braces (BRBs) in RC-BRBF was developed in this paper for solving the variable axial loading problem induced by BRBs. The proposed method provides a limit value of axial compression ratio for RC columns based on the equivalent axial compression ratio in order to ensure the ultimate lateral displacement capacity of the primary, the secondary, the third and the fourth level of RC columns could reach 2.7%, 2.4% and 2.1%, and provides a recommended ductility factor for RC columns based on the structural ductility capacity in order to achieve satisfactory ductility performance. It is shown that the limit value of axial compression ratio depends on the ultimate drift capacity as expressed by the equivalent axial compression ratio, and the ratio of the characteristic axial forces of the columns under the equivalent gravity and seismic actions, respectively. The improved method could effectively account for the influence of additional variable axial loads on the RC columns connecting to BRB, and ensure that RC columns could reach the limitation of ultimate lateral displacement capacity. The analysis results also reveal that the system economy could be enhanced though optimizing the section dimensions of RC column by the proposed method, and the RC-BRBFs meet ‘three seismic fortification levels’. Besides, the limitation of axial compression ratio factor is rational.