Geometry and Material Criteria for Low-Carbon Design of I/H-Beams in Sustainable Steel Structures Considering Both Mechanical Properties and Carbon Emissions

Construction steel is responsible for considerable amounts of carbon emissions in building sectors, and promoting the low-carbon design of steel components is conducive to the sustainable development of the industry. As one of the most typical components, I/H-beams are widely used in steel structures. In this paper, a new comprehensive index named carbon-capacity ratio (CCR) was proposed considering both mechanical properties and carbon emissions of I/H-beams, based on which the geometry coefficient and material coefficient were derived. Quantitative investigation was then conducted on the geometry coefficient to figure out the effects of different geometry variables, and the geometry criteria for low-carbon design of steel beams were concluded considering different load conditions. Results show that for double-symmetric cross-sections bearing flexural loads, larger flange width and beam height are suggested, while for single-symmetric cross-sections bearing flexural loads, increasing beam height as well as flange width and thickness can all contribute to sustainable beam designs, but adopting large beam height is the most effective. For cross-sections bearing shear loads, increasing beam height and web thickness would be beneficial. The feasible design domain (FDD) for geometry variables was proposed to be predicted with either linear or hyperbolic criteria depending on different loads and cross-sections. Additionally, a qualitative discussion was also given on the material coefficient, and steel with higher strength or that produced from recycled scrap using energy-saving technologies, as well as new prototyping techniques with lower energy and material loss, are recommended for beam fabrication. This study is expected to serve as a preliminary supplement to the blank in current codes or standards for low-carbon design of construction steel.