Steel reuse for sustainable design of large-span structures: The case of gridshells

Gridshells are lightweight spatial structures widely used for large-span constructions, offering high structural efficiency with minimal material usage. A key challenge in their sustainable design is integrating reclaimed steel elements to reduce environmental impact while maintaining structural performance. This study addresses this challenge by developing a stock-constrained optimization method, tested within the FreeGrid benchmark (https://sites.google.com/view/freegrid/home), to maximize the reuse of steel members while ensuring mechanical feasibility. A barrel vault gridshell is used as a case study with different grid configurations. The global performance is evaluated using three performance metrics, accounting for structural response, sustainability, and buildability. Due to the computational complexity of nonlinear analyses, a simplified method based on the Merchant-Rankine formula is introduced to estimate structural performance. The optimal solutions incorporating reused elements (ReBGs) are subsequently validated through geometrically and materially nonlinear analysis (GMNA) to verify their reliability. The results demonstrate that gridshells incorporating reclaimed steel achieve greater sustainability performance compared to conventional designs (BGs) while maintaining good structural performance. However, the irregular geometries generated during optimization negatively affect buildability, emphasizing the need for additional constraints in future developments. This study highlights that integrating reclaimed steel into gridshell design within the FreeGrid framework can effectively reduce environmental impact while ensuring structural efficiency, paving the way for broader applications in sustainable construction.