Life-cycle environmental impact optimization of an RC-THVS composite frame for sustainable construction

This study investigates the benefits of Life-Cycle Environmental Impact Optimization (LCEIO) in structural engineering, focusing on the RC-THVS composite typology as a sustainable alternative for frame-building construction. This innovative structural system integrates reinforced concrete (RC) columns with Transversely Hybrid Variable Section (THVS) steel girders serving as beam elements. The optimization problem is formulated to optimize the Global Warming Potential of the building structure during its life cycle. A novel LHS-CINS algorithm is introduced to solve the formulated optimization problems efficiently. Results show that LCEIO reduces environmental impact significantly, with optimized structures achieving up to a 32 % reduction in emissions compared to traditionally designed buildings. The most substantial improvement occurs in the manufacturing phase, where THVS girders lower emissions by up to 70 % compared to traditional I-section profiles. Additionally, maintenance-related impacts decrease by 45 % due to the girders' optimized tapered geometry. When comparing optimized solutions, rigid-joint composite typologies outperform RC systems in low-aggressiveness environments, reducing life-cycle emissions by 30 %. In highly aggressive environments, composite structures remain more sustainable than RC ones, although maintenance impacts are accentuated. Beyond individual component performance, THVS girders contribute to overall structural efficiency by reducing self-weight, thereby lowering axial loads on columns and foundations. Moreover, when slabs and walls are integrated into the superstructure, composite typologies further enhance system efficiency, cutting emissions by up to 42 % compared to bare frame models. The findings emphasize the capability of LCEIO and composite configurations to design more sustainable, efficient, and environmentally responsible building solutions.