Exploring new frontiers in gridshell design: The FreeGrid benchmark

Gridshell structures require an intricate design activity that shall comply with several design goals of diverse nature. This design phase can be approached with different methods and strategies and usually requires multiple competencies from different scientific fields. In this context, a common benchmark, called FreeGrid, is proposed to the scientific and practitioners’ communities in order to test and compare different approaches to the design and optimization of steel gridshells on the bases of ad-hoc defined performance metrics. FreeGrid sets three design baseline problems: a barrel vault, a parabolic dome, and a hyperbolic paraboloid, having their spring line partially not constrained (free-edge) and subjected to uniform and piecewise uniform load conditions. Participants are called to modify the baseline gridshell(s), observing a limited number of design constraints (related to geometry, external constraints and material), in order to improve their structural, buildability, and sustainability performances through the maximization of a bulk quantitative performance metric. Specifically, the structural performance metric accounts for both ultimate and serviceability behavior, through the calculation of the critical Load Factor and maximum vertical displacement; the buildability performance metric includes the evaluation of face planarity, uniformity of structural joints and members; the sustainability performance metric is based on the structure embodied carbon. This paper describes the baseline gridshells setups, the proposed performance metrics and the recommended method for performance assessment. The complete data of the baseline structures are made available according to an Open Data policy, together with postprocessing utilities intended to align the procedure to obtain the performance metrics.