The longitudinal bulkheads of the passenger ships are characterised by a presence of large openings necessary for the access to the balcony from the cabins, which are the cause of discontinuities in the stress flux resulting in a stress concentration at the corners of the openings, which may lead to fatigue damage. The stress concentrations are currently mitigated with an increasing of the plate thickness or by a modification of the structural configuration of the opening. The main objective of this study is to verify if the insert plate of high strength alloy steel can improve the fatigue performance of the opening corner by an increasing of the time to a crack initiation and propagation up to the critical crack size. The material properties are determined by the laboratory test carried out within the EU project MOSAIC. The as-built corner and the new structural configuration, which contemplates the use of the insert plate of the high strength alloy steel, are analysed by the finite element method. Fatigue damage is evaluated based on the SN approach, whereas the fatigue crack growth is estimated applying the fracture mechanics and the Paris Erdogan law. Finally, the consequences of the adoption of the solution with the HSLA insert plates in terms of weight and cost savings were evaluated and discussed.