Wind speeds over the world’s oceans have increased over the past two decades, as have wave heights. Studies of climate change typically consider measurements or predictions of temperature over extended periods of time. Climate, however, is much more than temperature. Over the oceans, changes in wind speed and the surface gravity waves generated by such winds play an important role. We used a 23-year database of calibrated and validated satellite altimeter measurements to investigate global changes in oceanic wind speed and wave height over this period. We find a general global trend of increasing values of wind speed and, to a lesser degree, wave height, over this period. The rate of increase is greater for extreme events as compared to the mean condition.

https://researchbank.swinburne.edu.au/file/bca43746-6f16-4ad2-a4b7-27f8d8d60fed/1/PDF (Published version).pdf

Global trends in wind speed and wave height over the past 25 years

Assessment of the efficiency of Kriging surrogate models for structural reliability analysis

A review of some representative floating wave energy converter (WEC) projects in the world, including the wave energy capturing technology, development history, main dimensions and tested sea sites is presented. The design essentials of WEC mooring system are discussed and a mooring system design procedure for WEC is proposed, which includes the introduction of related design codes and mooring analysis methods. In the last part, a comprehensive review of mooring system design in the current WECs projects is conducted. Different mooring systems and mooring materials are introduced and discussed. Based on the discussions, recommendations are made for the suitable mooring design according to the WEC's dimensions and working principles. It is shown that the elastic synthetic rope has great potential in the application of WEC mooring system, and the hybrid mooring system could be a good solution for WEC station keeping problem.

Review of mooring design for floating wave energy converters

Dynamic Bayesian networks based approach for risk analysis of subsea wellhead fatigue failure during service life

Prediction of wave-induced loads on ships: Progress and challenges

Climate change and safe design of ship structures

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Ship and Offshore Structure Design in Climate Change Perspective

Re-completion and re-drilling of existing wells and introduction of new large drilling rig systems are elements that have led to renewed focus on the fatigue capacity for existing and new subsea wells. Due to lack of applicable codes and standards for such fatigue calculations, a unified analysis methodology has been developed and described in a Wellhead Fatigue Analysis Method Statement (MS). The intention of this work is to reflect the best practice in the industry and to provide an important contribution to well integrity management. The analysis methodology is limited to fatigue damage from dynamic riser loads present during subsea drilling and work over operations. The analysis procedure may be divided into three parts. i) A local response analysis that includes a detailed finite element model from wellhead datum and below. Interaction between the structural well components and soil structure interaction is properly accounted for. The main result from this analysis is the load-to-stress curve that describes the relationship between the riser loads at the wellhead datum and the stress at the fatigue hot spots. The analysis also provides the lower boundary conditions of the global load analysis model. ii) A global load analysis where the floating mobile drilling unit (MODU) motions and wave loads on the riser are taken into account. The results are time series or load histograms of the loads at wellhead datum, with focus on the bending moment, in all relevant environmental sea states. iii) Fatigue damage assessment, where a mapping of the loads with the relevant load to stress curve is carried out together with subsequent fatigue damage calculation. Appropriate S-N curve is applied together with wave scatter diagrams for the relevant operations and durations. The final result is the accumulated fatigue damage. With a unified analysis methodology in place particular attention is placed on a structured and specified analysis input and output. Results are suggested presented as a function of time and also as a function of key analysis input parameters that are associated with uncertainty. These are prerequisites from a well integrity management perspective in ensuring analysis results that are comparable. This paper presents the essence of the Wellhead Fatigue Analysis Method that was developed in cooperation between Statoil and DNV. Currently this analysis methodology is under extension and revision in the joint industry project (JIP) “Structural Well Integrity During Well Operations”. 11 operators participate in this JIP which also has structured cooperation with equipment suppliers, drilling companies and analysis houses. The aim is to form a wellhead analysis recommended practice document.Copyright © 2011 by ASME

Wellhead Fatigue Analysis Method

Global warming and extreme weather events reported in the last years have attracted a lot of attention in academia, industry and media. The ongoing debate around the observed climate change has focused on three important questions: will occurrence of extreme weather events increase in the future, which geographical locations will be most affected, and to what degree will climate change have impact on future ship traffic and design of ships and offshore structures? The present study shortly reviews the findings of the Intergovernmental Panel on Climate Change Fourth Assessment Report, AR4, [1] and other relevant publications regarding projections of meteorological and oceanographic conditions in the 21st century and beyond with design needs in focus. Emphasis is on wave climate and its potential implications on safe design and operations of ship structures. A risk based approach for marine structure design accounting for climate change is proposed. The impact of expected wave climate change on ship design is demonstrated for five oil tankers, ranging from Product tanker to VLCC. Consequences of climate change for the hull girder failure probability and hence the steel weight of the deck in the midship region is shown. Recommendations for future research activities allowing adaptation to climate change are given.Copyright © 2011 by ASME

Torfinn Hørte

Papers

Climate change and safe design of ship structures

Ship and Offshore Structure Design in Climate Change Perspective

Wellhead Fatigue Analysis Method

Potential Impact of Climate Change on Tanker Design

Establishing an Industry Best Practice on Subsea Wellhead Fatigue Assessment