This Special Issue contains a selection of papers that have been presented at the OMAE2017 Special Symposium on Safety of Marine Structures and Operations in Honor of Professor Torgeir Moan, who has had a distinguished career dedicated to the general area of Ocean and Offshore Engineering.

Torgeir Moan is currently an Emeritus Professor of Marine Technology at NTNU, in Norway where he spent his academic career. He has been the Director of the Center of Ships and Ocean Structures (CeSOS) and is currently Senior Advisor to the Center for Autonomous Marine Operations and Systems (AMOS) at NTNU.

Professor Moan's main disciplines are structural analysis and design with a focus on integrated dynamic analysis and safety assessment—using numerical and experimental methods as well as in-service information. He has carried out research as well as engineering design and analyses of innovative concepts of high-speed vessels, LNG ships and FPSOs, oil and gas platforms, floating bridges as well as offshore wind turbines and wave energy converters.

Professor Moan has authored or co-authored approximately 650 journal and peer-reviewed conference publications (20% of which are OMAE publications), and a book on “Stochastic dynamic analysis of marine structures,” published by the Cambridge University Press (2012), together with Professor Arvid Næss. He has supervised more than 400 M.Sc. thesis work and about 80 Ph.D. degrees. From 2001 to 2018, Moan has been editor of the Journal of Marine Structures and serves on the editorial board of several other journals.

This symposium consisted of about 60 papers in 14 sessions, which ensured that there was one session running all the time from start to end of the Conference. The topics of the sessions are Offshore Renewable Energies (2 sessions), Floating Bridges (2 sessions), VLFS (1 session), Stochastic Dynamic Response (1 session), Marine Operations (2 sessions), Validation of Simulation Models (1 session), Design Codes (1 session), Fatigue Analysis (1 session), Inspection, and Maintenance (1 session), and Reliability and Risk Analysis (2 sessions).

The symposium and this special issue address safety of marine structures and operations. Experience shows that safety essentially depends on proper design codes, attitude, and competence of those doing the engineering, fabrication, and operations, and the quality of the methods applied as well as quality assurance and control. Design codes should refer to ultimate and fatigue limit states and address robustness by accidental collapse or progressive collapse limit states, in connection with accidental events and deterioration due to cracks and corrosion. Moreover, in view of the increasing availability of advanced and accurate tools—if applied with insight—there is a need to develop and validate simplified methods to save time and efforts. The uncertainties of methods and data need to be accounted for in the design by using load and resistance factors or direct reliability or risk analysis. The goal of the symposium was to share knowledge about theoretical methods and operational experiences that can be used to ensure future safe and efficient design and operations of various types of marine structures; such as, oil and gas platforms, ships, very large floating structures like bridges and terminals, and wind and wave energy convertors. Assessment of marine operations associated with sea transport and installation or decommissioning of marine structures or other marine operations is an emerging area of significant importance.

The papers included in this special issue address some of the topics mentioned. Lotsberg [1] presented a review of fatigue design standards, while Garbatov and Guedes Soares [2] dealt with corrosion, in particular on modeling its spatial variability. Both are very important topics related with the degradation processes that ship and offshore structures are subjected to since the initial phases of operation, and both need to be considered in design and in maintenance and inspection planning.

Iijima et al. [3] studied the uncertainty of wave-induced vibrations of large container ships due to ship operation an important aspect that is related to the hydro-elastic response of those structures. Fredriksen et al. [4] dealt with hydrodynamic aspects related with a floating bridge, a type of structure that has been attracting much interest in Norway in the last few years. Two papers dealt with collision problems, one a ship collision with a floating bridge [5] and the other about the collisions of a moored structure with moving broken ice driven by current and wave [6].

The last four papers deal with wind energy platforms, a topic that has attracted most of Professor Moan's attention in later years. The paper by Nejad et al. [7], his co-workers, deals with the effect of tower top accelerations on the drivetrain responses in a spar-type floating wind turbine. Kanner et al. [8] deals with the testing for power optimization of floating wind turbines using real-time hybrid testing with autonomous actuation and control. Utsunomiya et al. [9] deal with the numerical analysis of a hybrid-spar floating wind turbine, and Sclavounos et al. [10] discuss the offshore wind turbine nonlinear wave loads and statistics. It is interesting that these papers concentrate on the spar type of platform, which is the concept that has been initiated in Norway.

The set of papers in this special issue provide thus a diversified view of several problems of interest in Ocean Engineering and illustrate some of the interest areas that Professor Torgeir Moan has been addressing during his career. Torgeir Moan has been my Ph.D. supervisor and thus I was happy to organize this Symposium in his honor, and this follow up Special Issue of the ASME Journal of Offshore Mechanics and Arctic Engineering. Professor Zhen Gao, one of his more recent students, has acted as organizer of several topics of the Symposium, contributing also to its organization.

References

References
1.
Lotsberg
,
I.
,
2019
, “
Development of Fatigue Design Standards for Marine Structures
,”
ASME J. Offshore Mech. Arct. Eng.
,
141
(
3
), p.
031301
.
2.
Garbatov
,
Y.
, and
Guedes Soares
,
C.
,
2019
, “
Spatial Corrosion Wastage Modelling of Steel Plates Subjected to Marine Environments
,”
ASME J. Offshore Mech. Arct. Eng.
,
141
(
3
), p.
031602
.
3.
Iijima
,
K.
,
Ueda
,
R.
,
Tamaru
,
H.
, and
Fujikubo
,
M.
,
2019
, “
Numerical Investigation Into Uncertainty of Wave-Induced Vibration of Large Container Ships Due to Ship Operation
,”
ASME J. Offshore Mech. Arct. Eng.
,
141
(
3
), p.
031101
.
4.
Fredriksen
,
A. G.
,
Heiervang
,
M. F.
,
Larsen
,
P. N.
,
Sandnes
,
P. G.
,
Sørby
,
B.
,
Bonnemaire
,
B.
,
Nesteby
,
A.
, and
Nedrebø
,
Ø.
,
2019
, “
Hydrodynamical Aspects of Pontoon Optimization for a Side-Anchored Floating Bridge
,”
ASME J. Offshore Mech. Arct. Eng.
,
141
(
3
), p.
031603
.
5.
Sha
,
Y.
,
Amdahl
,
J.
, and
Dørum
,
C.
,
2019
, “
Ship Collision Analysis of a Floating Bridge in Ferry-Free E39 Project
,”
ASME J. Offshore Mech. Arct. Eng.
,
141
(
3
), p.
031601
.
6.
Su
,
B.
,
Aarsæther
,
K. G.
, and
Kristiansen
,
D.
,
2019
, “
Numerical Study of a Moored Structure in Moving Broken Ice Driven by Current and Wave
,”
ASME J. Offshore Mech. Arct. Eng.
,
141
(
3
), p.
031501
.
7.
Nejad
,
A. R.
,
Bachynski
,
E. E.
, and
Moan
,
T.
,
2019
, “
On Tower Top Axial Acceleration and Drivetrain Responses in a Spar-Type Floating Wind Turbine
,”
ASME J. Offshore Mech. Arct. Eng.
,
141
(
3
), p.
031901
.
8.
Kanner
,
S.
,
Koukina
,
E.
, and
Yeung
,
R. W.
,
2019
, “
Power Optimization of Model-Scale Floating Wind Turbines Using Real-Time Hybrid Testing With Autonomous Actuation and Control
,”
ASME J. Offshore Mech. Arct. Eng.
,
141
(
3
), p.
031902
.
9.
Utsunomiya
,
T.
,
Sato
,
I.
,
Kobayashi
,
O.
,
Shiraishi
,
T.
, and
Harada
,
T.
,
2019
, “
Numerical Modelling and Analysis of a Hybrid-Spar Floating Wind Turbine
,”
ASME J. Offshore Mech. Arct. Eng.
,
141
(
3
), p.
031903
.
10.
Sclavounos
,
P.
,
Zhang
,
Y.
,
Ma
,
Y.
, and
Larson
,
D. F.
,
2019
, “
Offshore Wind Turbine Nonlinear Wave Loads and Their Statistics
,”
ASME J. Offshore Mech. Arct. Eng.
,
141
(
3
), p.
031904
.