Fiabilidade de estruturas de navios reparados sujeitos a corrosao e fadiga

The objective of this thesis is to develop mathematical tools for the reliability assessment of ship hulls subjected to the degrading effect of corrosion and of fatigue on the longitudinal members. The effect of corrosion is presented as a time dependent process with two states. In the first one, there is no corrosion due to existence of coating protection. Upon failure of the protection system general corrosion decreases plate thickness and affects the midship section modulus. The potential cracks are considered to occur in the connections between longitudinal stiffeners and transverse web frames. The model accounts for the crack growth process applying linear elastic fracture mechanics. It is considered that a ship hull girder is subjected to the simultaneous action of corrosion and of fatigue in longitudinal members. The effect of both phenomena on the section modulus is accounted for and it is used as the reference variable to measure the reliability of the ship hull against collapse. The effect of maintenance actions is modelled as a stochastic process and it is accounted for considering that the repaired elements are restored to a state as new. Different repair policies are studied and the approach can be used as a tool to plan the maintenance action based on reliability resultsAvailable from Fundacao para a Ciencia e a Tecnologia, Servico de Informacao e Documentacao, Av. D. Carlos I, 126, 1200 Lisboa / FCT - Fundação para o Ciência e a TecnologiaSIGLEPTPortuga