A combined topology-sizing optimization approach for the sustainable design of steel gridshells with reclaimed bars

The paper introduces an innovative combined topology and sizing optimization methodology aimed at incorporating reclaimed steel elements into gridshell structures to minimize the use of new elements. The proposed approach considers both the optimal arrangement of reused components within the grid and the necessary configuration of new members to uphold structural integrity. The validity of the proposed methodology is substantiated through two case studies, one based on existing literature and the other inspired an actual gridshell, where various scenarios of reclaimed stocks are examined. Specifically, stocks characterized by varying numbers, lengths, and cross-sections of reusable members have been considered. The results of the different solutions are presented in terms of the structural weight of new members, buckling factor, maximum utilization ratio, maximum displacement, and greenhouse gas emissions. These outcomes are compared to those of a base case designed entirely with new elements. The comparison underscores the effectiveness of the proposed approach in delivering solutions that minimize the weight of new elements and reduce greenhouse gas emissions while ensuring the required performance in terms of strength and stiffness. These results underscore the potential of optimization strategies to foster sustainability in structural design without compromising performance.