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Partial safety factors for berthing velocity and loads on marine structures

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Author: Roubos, A. · Peters, D.J. · Groenewegen, L. · Steenbergen, R.D.J.M.
Type:article
Date:2018
Publisher: Elsevier Ltd
Source:Marine Structures, 58, 73-91
Identifier: 782491
Keywords: Berthing energy · Berthing impact · Berthing load · Berthing velocity · Marine structures · Partial safety factor · Navigation · Ocean currents · Ocean structures · Offshore structures · Structural design · Velocity · Wind effects · Berthing energy · Characteristic value · Design recommendations · Load and resistance factor designs · Safety factor · 2015 Fluid & Solid Mechanics · SR - Structural Reliability · TS - Technical Sciences

Abstract

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. © 2017 Elsevier Ltd