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Bienen B.,University of Western Australia | Gaudin C.,University of Western Australia | Cassidy M.J.,University of Western Australia | Rausch L.,FH Darmstadt | Purwana O.A.,Keppel Offshore and Marine Technology Center
International Journal of Offshore and Polar Engineering | Year: 2012

This paper establishes the undrained capacity of a circular skirted mat under uniaxial horizontal and moment loading, respectively, and presents the combined vertical, horizontal and moment (VHM) capacity envelopes for a novel concept for foundations that combines a skirted mat with a suction caisson. This foundation concept enables self-installation and preloading of the footing. Specifically, this research explores the effect of the central caisson on the failure mechanisms and the resulting VHM capacity through finite element analysis. The results demonstrate that the central caisson more than doubles the horizontal capacity while moderately increasing the capacity in the vertical and moment loading directions. © The International Society of Offshore and Polar Engineers.

Gaudin C.,University of Western Australia | Mohr H.,University of Western Australia | Cassidy M.J.,University of Western Australia | Bienen B.,University of Western Australia | Purwana O.A.,Keppel Offshore and Marine Technology Center
Proceedings of the International Offshore and Polar Engineering Conference | Year: 2011

To enable self-installation and suction-induced preloading of subsea foundations a novel hybrid foundation is being considered. The concept combines a skirted mat and one or more suction caissons with a skirt length that extends significantly beyond the mat skirt. This results in a significant contribution of the caisson to the overall foundation capacity. Centrifuge experiments have been undertaken to investigate the capacity of the hybrid foundation under combined vertical (V), horizontal (H) and moment (M) loading, relevant to offshore conditions. Tests were performed on hybrid foundations featuring a caisson with varying diameters and skirt lengths. The paper present results of horizontal translation tests, which are interpreted as failure envelopes and compared to existing envelopes for a skirted mat. The contribution of the central caisson to the change in shape and size of the mat failure envelopes are also quantified. Copyright © 2011 by the International Society of Offshore and Polar Engineers (ISOPE).

Palmer A.,National University of Singapore | Wei B.,National University of Singapore | Hien P.L.,National University of Singapore | Thow Y.K.,Keppel Offshore and Marine Technology Center
Proceedings of the International Conference on Port and Ocean Engineering under Arctic Conditions, POAC | Year: 2015

Ice jamming occurs when ice fills the space between the legs of a multi-legged structure. The jammed ice often has sufficient strength and size not easily to clear away from the legs, and the legs and the jammed ice may then act as a single structural unit. There are many analogous phenomena in the flow of fragmented solids through gaps. Relationships between ice jamming, leg dimension and leg-leg spacing are discussed in ISO 19906. The choice of leg diameter and leg spacing is an important design decision that affects the commercial value of the structure. The primary objective of the present study is to develop a deeper understanding of ice jamming events, in order better to formulate design loads on a multi-leg structure.

Celik S.U.,Fatih University | Bozkurt A.,Fatih University | Hosseini S.S.,Keppel Offshore and Marine Technology Center | Hosseini S.S.,Tarbiat Modares University
Progress in Polymer Science | Year: 2012

Fuel cells are gaining increasing attention as a clean and promising technology for energy conversion. One of the key benefits of fuel cells compared to other methods is the direct energy conversion that enables the achievement of high efficiency. The electrolyte membrane is the most essential parts of a fuel cell unit, and consequently has been the subject of considerable research and development. Among the various types of proton conducting electrolytes examined for fuel cell applications, polymer electrolyte membranes (PEMs) are regarded as viable candidates since they enable operation of the cells at desirably low temperatures. This review describes recent progress in the design and development of high performance proton conducting PEMs, including the analysis of the design requirements and strategies for development of advanced PEMs for operation in anhydrous conditions. Some of the most widely used types of azole heterocycles are introduced and compared, particularly in terms of their performance characteristics in polyacids containing different functional groups. In addition, the latest research studies and progress in the field of azole-containing and azole-functionalized electrolyte systems are discussed and reviewed. © 2011 Elsevier Ltd.

Perry M.J.,Keppel Offshore and Marine Technology Center | Mobbs C.B.,LeTourneau Technologies
Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE | Year: 2011

The Drag-Inertia method is one of the most popular time domain methods for estimating the contribution of dynamics to the response of a Jackup. The method calculates the Dynamic Amplification Factor (DAF) using the simulated response of the Jackup to a short, usually one hour, random storm. The Drag-Inertia method has been subject to some criticism as it produces results which are, in some cases, less conservative than other methods. Despite this, we feel the benefits of the Drag-Inertia method; efficient and repeatable assessment, are essential to a site assessment. Other methods, such as the Winterstein method, require much longer storm durations, while the variability in DAF results is considerably more. In this study, we propose that factoring the DAFs produced by the Drag-Inertia method is a practical way to improve conservatism, bringing the DAFs in line with the mean DAF results produced by the Winterstein method. The factor is proposed based on simulations of 18 different Jackup configurations and eight different wave conditions. The simple factor is a function of period ratio, Tn/Tp, allowing for efficient and repeatable factoring of DAF values without additional simulation time. When the factor is applied to the Drag-Inertia DAF values the resulting DAFs are within 0.05 of the mean Winterstein DAF in 61% of cases and in only 7% of cases is the Winterstein DAF more than 0.10 above the factored Drag-Inertia result. Copyright © 2011 by ASME.

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