Flexural behaviour of reinforced concrete beams with voids: Topology optimisation basis

The production process of Portland cement, one of the main components of concrete, is the main reason for the high environmental impact of the world’s primary building material with its high carbon dioxide (CO 2 ) emissions. Over the years, researchers have developed a range of methods to minimise the carbon footprint of concrete structures, on the one hand on the material side and on the other hand by optimising the structure. The presented study concentrates on enhancing resource efficiency in reinforced concrete (RC) structures via topology optimisation of RC beams. The approach is based on voiding the RC beams along their longitudinal and/or cross-sectional axis using four simple geometric shapes (circular, square, hexagonal, and triangular). The goal is to facilitate an automated and resource-efficient design and production process using a simultaneously developed shuttering system. Therefore, a comprehensive parameter study was conducted using Finite Element Calculations considering the nonlinear behaviour of reinforced concrete. The computational results are promising and show possible savings of around 19.2 % of concrete volume while still using ordinary materials (concrete with a characteristic strength of 35 MPa and reinforcing steel with a yield strength of 550 MPa) as well as the same boundary conditions and dimensions as the solid RC beam designed according to Eurocode 2. In addition, it can be proven that the achieved failure mode matches that of the reference beam, exhibiting a ductile flexural failure. The study results will serve as the foundation for further investigations to construct a topology optimisation strategy for RC horizontal elements. The creation of truss configurations through the development of strut-and-tie models, and the utilisation of optimisation software will be within the main scope of work. • Voiding reinforced concrete beams does not necessarily result in a decrease in the load-bearing capacity. • Topology optimising reinforced concrete beams offers significant potential without needing ultra-high-performance materials. • Topology optimisation of reinforced concrete beams can keep boundary conditions like those of standard beams.