[提要]  对压弯构件在跨中设置侧向支撑和扭转支撑时的稳定性进行研究，先就一般情况建立平衡微分方程，推导出压弯构件的稳定临界方程，在此稳定临界方程的基础上对偏心支撑压弯构件进行详细的分析，得到了使压弯构件计算长度减半的扭转支撑临界刚度表达式和侧向支撑临界刚度表达式，导出了判断支撑是否能使压弯构件计算长度减半的临界荷载偏心。此外还分析了非完全支撑时支撑刚度和构件承载力的关系，以及侧向支撑、扭转支撑及两者联合作用对构件承载力的影响，推出了上面所有分析的解析式。
[关键词]  支撑  梁-柱  压弯构件  刚度  弯扭屈曲  计算长度

The elastic stability of beam-column with lateral and torsional braces at mid-span is studied. Firstly the stability critical equation of laterally and torsionally braced beam-column is derived. Based on the equation derived, the formulae for critical bracing stiffness( either lateral brace or torsional brace) and critical load eccentricity are presented which can have the effective length of beam-column. Then the load capacity is investigated when the brace can't halve the effective length of beam-column and the relationship between load capacity and bracing stiffness is presented. Moreover, effect of lateral brace's location on the load capacity of beam-column and co-action of lateral and torsional braces are studied. And the closed-form solutions are given.
Keywords: brace; beam-column; bracing stiffness; flexural-torsional buckling; effective length