Finite element analyses of a wave loaded pile : deterministic and probabilistic
Master Thesis
1991
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University of Cape Town
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Abstract
The problem of pile stick-up, where the pile has been stabbed into the pile guide of the platform to be fixed to the sea-bed and is loaded by the current and waves of the ocean, was recently of concern when the fixation of the first local offshore production platform took place. A previous investigation considered the resonant behaviour of the undriven pile subjected to various predicted sea states and various methods were examined to limit the large displacements anticipated. In the present work, a refined model of the problem is developed using the ABAQUS finite element program. Of particular interest is the applicability of the , probabilistic finite element method (PFEM). It is important to appreciate that a mere deterministic dynamic analysis - however accurate analytically - may be of limited value when applied to structures in the ocean. The response achieved thus will either be unelegantly conservative or very unreliable due to the many uncertain parameters that pervade the field of structural dynamics in the ocean. Traditionally, statistical methods are reverted to with uncertainty analyses, but they seldom have much appeal because of the computational effort involved. The PFEM was found quite attractive with a formulation where the uncertainty of the drag coefficient and the inertia coefficient were investigated. It was concluded that the uncertainty in these coefficients should be limited to a coefficient of variation of approximately 20% and that the simplified model on which the formulation was based should be refined if acceptable results for the purposes of design were required.
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Includes bibliography.
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Grant, C. 1991. Finite element analyses of a wave loaded pile : deterministic and probabilistic. University of Cape Town.