OPTIMUM DESIGN OF UNBRACED RIGID FRAMES

In this paper, an algorithm is presented for the optimum design of unb raced rigid frames which takes into account the non-linear response of the frame due to the effect of axial loads. It considers sway constra ints and combined stress limitations in the design problem. While the optimality criteria approach is employed to handle sway limitations, t he combined stress constraints are reduced to non-linear equations of the design variables. The algorithm initiates the design process by ca rrying out non-linear analysis of the frame. It checks the overall sta bility in every iteration of the analysis. When the non-linear respons e of the frame is obtained without loss of stability, the new values o f design variables are computed from the recursive relationships. This process of re-analysis and resizing is repeated until the convergence is obtained. A number of tall steel frames are designed by the algori thm as examples. (C) 1998 Published by Elsevier Science Ltd. All right s reserved.