Corrosion/repair modelling and reliability analysis of retrofitted complex tubular steel structures. 2026. Montilla.S; Bosse.R; Gidrão.G; Picón.R; Beck.A; Flórez-López.J.

This paper investigates the seismic reliability of complex tubular structures, such as offshore platforms, bridges, and buildings, located in corrosive environments that require structural repair. It proposes a novel method to assess the reduction in seismic resistance caused by corrosion by comparing fragility curves representing the structure’s initial and current states. Additionally, the method predicts the effectiveness of various retrofit strategies through the analysis of their updated fragility curves. First, a mathematical formulation is introduced to describe structural behavior under severe chemical and mechanical loading, utilizing a multiscale analysis approach. This model accounts for the effects of corrosion and repair using fiber-reinforced polymers on the progression of local buckling induced by mechanical overloads, such as impacts and earthquakes. The local analysis employs geometrically nonlinear plasticity within the shell theory framework at the elemental level. At the structural level, a new model based on Lumped Damage Mechanics (LDM) is proposed. The paper then applies Performance-Based Earthquake Engineering (PBEE) principles to derive fragility curves. Because LDM models incorporate internal damage variables, the innovative procedure presented here uses limit states of these variables to define failure probabilities. Finally, a case study of a structural retrofit is presented, demonstrating the accuracy of both the local buckling and LDM models. This example simulates the response of a structure subjected to corrosion and repair processes combined with seismic loading at various stages throughout its service life.