Computer‐Automated Design of Semirigid Steel Frameworks

This paper presents an efficient computer‐automated method for the optimum design of steel frameworks accounting for the behavior of semirigid connections. The method explicitly accounts for both connections and members by taking connection stiffnesses and member sizes as continuous‐valued and discretevalued variables to the design process, respectively. A continuous‐discrete optimization algorithm is applied to minimize the ‘cost’ of the connections and members for the structure subject to constraints on stresses and displacements under specified design loads. Two steel framework examples are presented to illustrate the features of the design method. It is shown that the design optimization determines connection stiffnesses that are entirely consistent with those for the actual (bolted/ welded) connections employed in conventional steel frameworks, but that member sizes are somewhat different from those found when the connections are (artificially) assumed to be fully rigid. That is, the results suggest that the proposed semirigid design method realistically accounts for connection behavior and produces more appropriate member sizes than does the traditional fully rigid design method.