Partial safety factors for berthing velocity and loads on marine structures

• Published in: Marine structures Vol. 58; pp. 73 - 91
• Main Authors: Roubos, Alfred, Peters, Dirk Jan, Groenewegen, Leon, Steenbergen, Raphael
• Format: Journal Article
• Language: English
• Published: Barking Elsevier Ltd 01.03.2018; Elsevier BV
• Subjects: Berthing; Berthing energy; Berthing impact; Berthing load; Berthing velocity; Design; Design factors; Extreme value theory; Extreme values; Impact loads; Limit state design; Load; Load resistance; Loads (forces); Marine structures; Navigation; Offshore structures; Partial safety factor; Probability theory; Safety; Safety factors; Soil; Stiffness; Structural design; Structural engineering; Tidal currents; Tidal energy; Tidal power; Velocity; Vessels; Berthing energy; Partial safety factor; Berthing impact; Berthing load; Marine structures; Berthing velocity
• ISSN: 0951-8339; 1873-4170
• DOI: 10.1016/j.marstruc.2017.11.003

Design methods for marine structures have evolved into load and resistance factor design, however existing partial safety factors related to berthing velocity and loads have not been verified and validated by measurement campaigns. In this study, field observations of modern seagoing vessels berthing in Bremerhaven, Rotterdam and Wilhelmshaven were used to evaluate partial safety factors for berthing energy and berthing impact loads. Various types of vessels and navigation conditions were statistically examined. The results show that characteristic values of berthing velocity with a return period of 50 years are in line with design recommendations in literature. Design values of berthing velocity are sensitive to the number of berthing operations during the lifetime of a marine structure. Typical partial safety factors for sheltered and exposed navigation conditions were derived by extrapolating distribution fits and applying extreme value theory. Differences in structural response due to soil stiffness and the type of berthing system installed influence partial safety factors for berthing impact loads. The probability of an uncontrolled berthing event was higher for exposed navigation conditions (strong tidal currents). In these circumstances, higher partial safety factors for berthing velocity should be considered in the design of marine structures. When berthing aid systems are used, the probability of extreme berthing velocities is lower, resulting in lower partial safety factors. The key findings of this study could be beneficial for the structural design of new and lifetime extension of existing marine structures. •Approximately 1948 berthing records, collected in Germany and the Netherlands, were statistically examined.•The characteristic berthing velocities found were generally in the range of recommendations in literature.•Partial safety factors did not show a correlation with vessel size and are not fixed.•Partial safety factors depend on navigational conditions and are influenced by application of berthing aids systems.•The existing design guidelines were considered to be safe for most situations.