FATIGUE OF SHIP STRUCTURAL DETAILS - TECHNICAL DEVELOPMENT AND PROBLEMS

During the past five years, a joint industry-government sponsored rese arch project titled the Ship Structural Maintenance Project (SMP) has been conducted at the Department of Naval Architecture & Offshore Engi neering, University of California at Berkeley, As a part of this proje ct, the fatigue damage of ship structural details has been extensively studied. This paper summarizes the technical development in fatigue a ssessment of ship structural details developed during this project. In the fatigue resistance model, the fatigue damage evaluation of struct ural details was based on a stress range/number-of-cycles-to-failure ( SN) approach in which the nominal stress procedure and the hot spot st ress procedure were employed, The fatigue assessment of cracked struct ural details was based on a cracked SN approach developed by a hybrid SN-FM (fracture mechanics) methodology. This cracked SN approach was f urther developed to incorporate load-shedding effects. In the fatigue loading model, a new formula for the damage correction factor associat ed with a wide-banded load process was developed. The random loading s equence for ship service was addressed. Fatigue reliability models wer e then reviewed and the different fatigue reliability updating procedu res were evaluated, These techniques were employed in the fatigue anal ysis of structural details in three tankers. Analysis results from the se three ships were presented to illustrate the technical developments and problems associated with fatigue assessment of ship structural de tails.