Interactive Design of Semirigid Steel Frames

A computer-based analysis and design method is presented for the design of semirigid steel frames. A second-order nonlinear analysis is used, which includes the effects of the flexibility of the connections and the geometric nonlinearity of the members, in conjunction with the LRFD specification of the AISC. The Frye and Morris polynomial model is adopted for modeling the semirigid connections. The design procedure is iterative and interactive in nature, and gives options to the engineer, interacting with the computer, to change member sizes and connections details for economic and practical considerations. Several examples are presented to demonstrate the validity and effectiveness of the design procedure for semirigid frames. It is shown that designs with greater economy may be realized with semirigid connections by a variation of connection stiffness that balances the span and end moments in a beam. The examples also demonstrate the more significant effect of connection flexibility on drift in unbraced frames.