Design of innovative modular systems based on life cycle assessment and optimization of inter-modular connections

Climate change is a significant contemporary challenge, considering recent European directives aimed at promoting more efficient resource use in buildings. In fact, the construction sector accounts for approximately 36% of global CO₂ emissions. Modular steel buildings emerge as a promising solution to reduce environmental impact due to the efficiency of prefabrication, the recyclability of steel, and the possibility of reuse of elements. However, the high carbon impact of steel production makes it necessary to optimize its use. This study focuses on the Life Cycle Assessment (LCA) of modular steel constructions, proposing a methodology to evaluate the optimal use of the material in relation to structural performance requirements in order to assess the Embodied Carbon (EC) in the materials used, allowing for more sustainable design choices. The methodology is applied to a modular case study designed according to defined architectural criteria and evaluated against sustainability parameters such as carbon emissions, assembly efficiency, reusability, fire resistance, and thermal and structural properties. The case study is also used to analyze different configurations of inter-modular connections, a key component of the overall system behavior. Starting from the literature review, three inter-modular connection solutions with vertical plug-ins are proposed and evaluated by nonlinear static (pushover) and cyclic analyses. Some results show that, for the same structural performance, steel is less sustainable in some cases than alternatives such as wood X-Lam. In addition, the behavior of the inter-modular connection with vertical plug-in is highly influenced by the geometry of the horizontal connection plate and its combination with other elements, such as the resilient layer introduced in one of the proposed connections. This work aims to contribute to the advancement of sustainable, high-performance modular building systems in line with global decarbonization goals. It also identifies the best compromises between constructive simplicity and structural performance, starting with a defined logic of behavior for the entire system