Boundary-oriented optimization of semi-rigid connections in steel frames using BNSGA

In recent decades, scholars have focused their research on optimizing semi-rigid frame structures. However, in most studies, semi-rigid connections are commonly treated as design variables without undergoing optimization during their construction phase. Considering that connection design encompasses multiple parameters, incorporating these design parameters as structural optimization variables could exponentially expand the search domain. To address the abovementioned issues, this study introduces a pre-optimization method for semi-rigid connections based on the boundary-oriented non-dominated sorting genetic algorithm (BNSGA). By adopting the Eurocode 3 (EC3) component method to calculate the moment-rotation curve of connections and utilizing cost as the objective function, the distribution of connection boundary surfaces in the initial stiffness-bearing capacitylowest cost objective space is determined using the BNSGA. Through the maximum direct distance strategy (MDDS), typical connection points are selected from the fitting points on the boundary surface based on construction parameters and performance metrics. The effectiveness of this approach in generating a connection database is further validated by analyzing two structural optimization examples.