Optimal design of planar frames based on stability criterion using first-order analysis

A design-oriented method for improving the strength and overall stability of moment-resistant framed structures is proposed. The method uses well-accepted approximate expressions of second-order phenomena to identify critical structural components to be modified in subsequent iterations. The optimization procedure uses an instability coefficient as a surrogate for the dominant eigenvalue of the linearized buckling problem. The method is readily implemented in a design-office setting and requires data from only a first-order analysis of the structure, thereby avoiding the specialized second-order calculations associated with other approaches to the treatment of stability in design. The proposed method can be implemented as a story-by-story procedure that is easily visualized for new designs.