Jack-up response to wave-in-deck loads during extreme storms

Howarth, M.J.; Dier, Aleksandra; Jones, W.D.; Hunt, Rupert J.

doi:10.1016/j.marstruc.2004.08.010

Cited by 9 publications

(3 citation statements)

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“…Suchithra and Koola (1995) carried out studies on the impact loads acting on horizontal slabs during wave slamming and concluded that wave slamming coefficient (C S ) depends on the air entrapped between the deck and the water surface. Howarth et al (2004) modified the studies done by MSL Engineering Ltd. (2001) to include the dynamic behaviour during the slamming of deck but concluded that vertical forces developed in the deck are mainly due to buoyant forces and the response of the jack-up structure towards the loads was static. It was recommended that dynamic amplification factor (DAF) shall not be applied for wavein-deck loads.…”

Section: Literature Reviewmentioning

confidence: 99%

Experimental investigation of the wave slam and slap coefficients for array of non-circular section of offshore platforms

Sekhar

Nallayarasu

2013

Ships and Offshore Structures

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The offshore platforms are generally designed with sufficient vertical clearance from the maximum predicted wave crest elevations. This vertical clearance is termed as 'air gap'. However, due to compelling reasons of hydrocarbon processes and also due to the increase in water levels due to climatic changes or seabed subsidence due to reservoir subsidence, the lower decks may become vulnerable to wave action due to reduction in air gap. The structural elements in the lower decks may become prone to wave-induced loads caused by high wave crests. The assessment of such wave-induced loads on the lower deck and supporting structures, especially in the existing platforms, becomes very essential for the continued safe operations. In the case of wave slamming on a structure, these supporting structural members will also be prone to large loads. Circular sections are commonly used for substructures due to their hydrodynamic efficiency; however, for deck structure, it is very common to use non-circular sections for supporting superstructure loads. The non-circular sections used in the lower decks get exposed to wave-induced loads. The imposed loads could be of higher magnitude compared with the circular sections due to the flat surface of the sections. A review of the literature indicates that the previous studies focused mainly on the circular sections and not much information is available on the non-circular shapes, especially in the case of wave slam and slap. The current study was focused on the measurement of wave-induced slam and slap loads on an array of non-circular sections in a laboratory wave flume and the estimation of force coefficient based on drag-based empirical equations. The studies revealed that the slam and slap coefficients for non-circular shapes are greater than those for circular shapes.

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Section: Literature Reviewmentioning

confidence: 99%

Experimental investigation of the wave slam and slap coefficients for array of non-circular section of offshore platforms

Sekhar

Nallayarasu

2013

Ships and Offshore Structures

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“…Cassidy (1999) performed a dynamic analysis considering the force-resultant model of the soil. Howarth et al (2004) performed a dynamic analysis considering two coupled linear and nonlinear spudcans. Nataraja et al (2004) obtained the fixity and damping of the seabed on the basis of real measurements and SNAME T and R 5-5A.…”

Section: Introductionmentioning

confidence: 99%

Soil-structure interaction analysis of jack-up platforms subjected to monochrome and irregular waves

Korzani

Aghakouchak

2015

China Ocean Eng

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As jack-up platforms have recently been used in deeper and harsher waters, there has been an increasing demand to understand their behaviour more accurately to develop more sophisticated analysis techniques. One of the areas of significant development has been the modelling of spudcan performance, where the load-displacement behaviour of the foundation is required to be included in any numerical model of the structure. In this study, beam on nonlinear winkler foundation (BNWF) modeling-which is based on using nonlinear springs and dampers instead of a continuum soil media-is employed for this purpose. A regular monochrome design wave and an irregular wave representing a design sea state are applied to the platform as lateral loading. By using the BNWF model and assuming a granular soil under spudcans, properties such as soil nonlinear behaviour near the structure, contact phenomena at the interface of soil and spudcan (such as uplifting and rocking), and geometrical nonlinear behaviour of the structure are studied. Results of this study show that inelastic behaviour of the soil causes an increase in the lateral displacement at the hull elevation and permanent unequal settlement in soil below the spudcans, which are increased by decreasing the friction angle of the sandy soil. In fact, spudcans and the underlying soil cause a relative fixity at the platform support, which changes the dynamic response of the structure compared with the case where the structure is assumed to have a fixed support or pinned support. For simulating this behaviour without explicit modelling of soil-structure interaction (SSI), momentrotation curves at the end of platform legs, which are dependent on foundation dimensions and soil characteristics, are obtained. These curves can be used in a simplified model of the platform for considering the relative fixity at the soilfoundation interface.

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“…The scholars have paid attention to the jackup platform for a long time. Their research on the jackup include wide-ranging subjects such as the fluid-structure-soil interaction analysis (Bienen and Cassidy 2006;Gaudin et al 2011), the key substructures' strength analysis (Zhang et al 2012), fatigue and fracture analysis (Morandi et al 2001;Shabakhty 2011), the response analysis under extreme condition (Cassidy et al 2002;Tan et al 2003;Howarth et al 2004;Jensen and Capul 2006) and so on. However, the process of lifting up or down the huge, heavy legs that combine * Corresponding author.…”

Section: Introductionmentioning

confidence: 99%

Influence of the legs underwater on the hydrodynamic response of the multi-leg floating structure

Chen

Huang

et al. 2014

Ships and Offshore Structures

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The wind farm installation vessel is a floating structure with multiple legs. The legs underwater have a prominent effect on the responses of the vessel on waves. The main factor is that the existing of the legs under water leads to the hydrodynamic characteristics different from the normal vessel without legs. To analyse the influence of the legs underwater on the hydrodynamic responses, five cases are classified according to the length of the legs under water. Then, the hydrodynamic responses of the structure in different cases are numerically simulated by applying the three-dimensional potential theory. The hydrodynamic coefficients, wave excitation loads and RAOs of the six degrees of freedom in different wave frequencies are calculated and compared. The results show that the effects of the legs underwater on the hydrodynamic response of a floating structure with multiple legs are visible except for heave motion of the floating body.

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Jack-up response to wave-in-deck loads during extreme storms

Cited by 9 publications

References 0 publications

Experimental investigation of the wave slam and slap coefficients for array of non-circular section of offshore platforms

Experimental investigation of the wave slam and slap coefficients for array of non-circular section of offshore platforms

Soil-structure interaction analysis of jack-up platforms subjected to monochrome and irregular waves

Influence of the legs underwater on the hydrodynamic response of the multi-leg floating structure

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