Optimal Design of Sustainable Concrete Shells with FRP Reinforcements

Concrete shell structures combine structural and material efficiency with architectural elegance. Despite their potential benefits, they are rarely adopted in everyday construction due to a lack of established design methods and durability concerns related to steel reinforcement corrosion, which is exacerbated by thin concrete sections. To address this challenge, this paper presents a method for optimizing the design of concrete shells reinforced with noncorrodible fiber-reinforced polymer (FRP) rebars. The proposed approach comprises a package of form-finding, reinforcement design, and sustainability-based optimization within a parametric design environment. The form-finding process employs the force-density method, while the design method is intended to be adaptable across various shell types by accounting for both membrane and flexural regimes. The proposed reinforcement design algorithm is based on equilibrium conditions for the limited ultimate state of the reinforcement and cracked concrete, ensuring that sections are over-reinforced to achieve pseudoductility in FRP-reinforced concrete shells. The shell optimization procedure demonstrates efficiency, with findings indicating that optimizing geometry and material use can significantly reduce carbon emissions. A case study featuring a 15 × 15-m structural system supported by columns at the four corners demonstrates that the proposed framework enables the design of an optimized shell, reducing embodied carbon by 40% compared with a flat slab with an equivalent plan area. The study is further validated by a geometrically and mechanically nonlinear finite-element model of the designed system, which enables assessment of its behavior under sustained loads. The optimized shell meets the serviceability criteria for long-term deflection, demonstrating how combining FRP reinforcement with geometry and material optimization can enable sustainable, durable, and lightweight concrete shells.