This note has emerged as a result of developing deterministic procedures for seismic design of braced steel frames. According to the capacity design procedure, braces are chosen as the primary seismic resisting elements, which produce the overstrength axial tension and compression actions. These overstrength brace actions are then used to design the secondary elements such as beams, columns and connections. Fundamental to the capacity design philosophy is the need to be able to estimate the maximum design actions that secondary members in concentrically braced frames must be able to resist after the braces buckle. It appears that the maximum seismic actions in secondary members are dependent on the post-buckling strength of braces in a seismic-resisting system. The experimental data compiled from different sources were compared with the analytical expressions for the brace compression strength reduction factor employed by some seismic design codes. The levels of reduction in the brace compression capacity have been identified, and a new analytical expression for the brace compression strength reduction factor has been proposed. © 1998 Elsevier Science Ltd.