The repair cost over the lifetime for caisson breakwaters covered with wave-dissipating blocks is estimated. The repair cost is estimated as the sum of the cost for repairing the wave-dissipating works and the cost equivalent to the amount of damage to the harbor area. In this study, it is assumed that the subsidence of the crest height of the wavedissipating works due to wave attacks causes the increase in the transmitted wave height behind the breakwater. The variations of the repair costs under several conditions are discussed.
Effective repair of coastal structures is very important. The percentage of the coastal structures constructed more than 30 years ago is increasing in Japan. In general, the performances of old structures are reduced and the maintenance cost for old structures is increased. However, the budget for replacing old structures with new structures is very limited. Under these circumstances, existing coastal structures need to be effectively repaired in order to save the cost. In the repair, the maintenance costs for the coastal structures need to be minimized because too frequent repair needs high repair cost; however, insufficient repairs may lead to catastrophic damage to coastal structures and surrounding area. Repair of coastal structures, e.g., breakwaters, should be determined on the basis of the decrease in the breakwater performances; this will help reduce the maintenance costs of the breakwaters during their designed lifetime, i.e., life cycle cost. However, the repair of breakwaters is currently determined on the basis of the degree of the displacement or the deformation of breakwaters. Recently, several studies on lifecycle costs for coastal structures including repair costs have been studied. Matsubuchi and Yokota (1999) investigated the lifecycle cost of berthing facilities. Nagao and Matsubuchi (1999) estimated the lifecycle cost and allowable failure probability of composite breakwater.
