Analysis of tubular structures subjected to extreme loading and corrosion/repair processes

Complex tubular structures are often exposed to aggressive environments that produce corrosion and, occasionally, must be able to withstand extreme mechanical overloads. Thus, health monitoring, computational simulation tools, and repair projects are critically required to assure the fulfillment of the expected service life. A very important retrofitting technique consists of the use of carbon fiber-reinforced polymers. This paper proposes a new multi-scale formulation that describes the coupling of corrosion/repair processes with plasticity and local buckling effects, specifically adapted for the analysis of complex structures. A lumped damage model is proposed that includes corrosion laws in the constitutive equations. Coupling between corrosion, repair, plasticity and local buckling is carried out by extended "interaction diagrams". Repair is characterized as a "negative corrosion increment". The structural assessment is carried out by the introduction of a "damage driving rotation" that determines the closeness of local buckling during cyclic loadings. Collapse risks are evaluated by using a local buckling state variable. This new model is implemented as a finite element in which corrosion is a nodal degree of freedom. This computational tool can be used for the design of deterministic or reliability-based management of inspection, maintenance, or repair of offshore and other complex tubular structures.