Welding is the primary joining technique used in ship structures. A ship structure contains many miles of welding which results in complex tensile residual stress distributions because of the geometrical constraints upon the components as they are welded. In subsequent operation, ship structures are exposed to complex cyclic loads and the residual stress distribution in stiffeners and plates are seen to be different from the as-welded residual stresses. They will have relaxed or redistributed according to the load levels during operation. One example of this is the elastic shakedown phenomenon which is a plastic deformation accompanied with a change in residual stress during the first (or first few) cycle followed by an elastic response, and this is called shake-out effect. Of particular interest in ship structures are the longitudinal stiffeners and transverse members which are welded onto the bottom decks as load bearing members. The longitudinal end connections in a double bottom configuration are critical to fatigue crack growth. Although the structure is considered to be safe after elastic shake-down, it is necessary to understand the redistributed residual stresses following the shake-down for a better understanding of long-term hull stresses and fatigue crack growth. The aim of this research project is therefore to study the effects of shakedown on residual stress redistribution and its consequence in the welds in the double bottom members of a ship structure. This is a difficult problem to model effectively because of the variability associated with the weld.