Advanced Nonlinear Analysis and Life Cycle Assessment of a Retrofitted Steel Portal Frame for Continued Use

Abstract This study presents a detailed investigation into the retrofitting of an aging steel portal frame, originally serving as a parking facility for public transport. As part of a broader strategy for extending the service life of existing structures, it combines advanced modelling with life cycle assessment to evaluate the technical and environmental benefits of retrofitting. The structure, featuring welded and bolted joints with lateral stability from a concrete shear wall and Saint Andrew's cross bracing, was surveyed using 3D laser scanning. This enabled a precise digital model for further analysis. A 3D nonlinear finite element model was built in Abaqus, accounting for all nonlinearity sources. Shell and solid elements were used to model structural parts and connections. Several retrofitting options were examined for service and ultimate limit states. Key outcomes include advanced modelling techniques for structural analysis and environmental impact evaluation of retrofitting through comparative LCA. The study demonstrates the potential of retrofitting for the continued use of existing steel structures.