Analysis of offshore jack-up platform under static and dynamic loading

Other Title(s)

تحليل منصة بحرية متنقلة تحت أحمال مستقرة و حركية

Dissertant

Mizuhi, Khudayr Aklu

Thesis advisor

Nassar, Amin A.

Comitee Members

Ulaywi, Jawad Kazim
Ali, Anis Abd al-Khidr Muhammad
al-Hilfi, Aziz H.
Hassan, A. K. F.
Jwig, Muhsin J.

University

University of Basrah

Faculty

Engineering College

Department

Department of Mechanical Engineering

University Country

Iraq

Degree

Ph.D.

Degree Date

2012

English Abstract

-There are several reasons for the increasing demand for the use of offshore jack-up platform.

One of them is the need of drilling oil wells at.

The other is to use this kind of jack-up as a portable supporting base to the Iraqi Navy because of the nature of Iraqi coasts. Confidence in jack-up platform use in normal and harsher environments requires jack-up analysis techniques to reflect accurately the physical processes occurring.

ANSYS is used as an analysis tool to estimate the non-linearity of interactions between jack-up structure, foundations, environment and seabed soft clay. A new jack-up structure under Lloyds Register Rules is designed according to Iraqi requirements, depth and environment of work site .

The model was created for a jack-up platform based on non-linear elastic beam theory.

Hollow pipe element type is used in the modeling. The structure is tested several times under its own weight.

It is supported ( six degree of freedom constraint) at several set points.

A suitable set point is chosen according to Von Misses stress criteria as the best locations to join the structure with its legs. Environmental conditions were taken to present loads in static and dynamic structural analysis.

Loads due to winds, currents and waves are computed according to the drag force and Morrison‟s equation.

Jack-up structure is tested under normal and harsh sea conditions. IV Interaction between foundations, environment and soft clay in three dimensions are analyzed.

Drucker- Prager criteria is used to present the North Arabian Gulf seabed soil (soft clay).

This three dimensional analysis shows the mechanical behavior of seabed down to 60 m of depth.

The study also shows the mechanical behavior of jack-up foundations. The work proves that the hollow pipe (PIPE16) element types gives reasonable results.

It offers to the model a constant section modulus and six degrees of freedom.

The work estimates the best points in the structure to join with legs according to Von Mises criteria and other mechanical parameters.

The work shows the maximum shear stress occurs at the joining points between structure and legs.

This result predicts the failure due to operating.

It must be treated with this problem by stiffening these locations.

Again the study indicates, that the deflection happens at ends of the structure.

The wave force with time period of 8 sec causes maximum deflection to occur at the beginning of wave impact then the deflection reduces through time progress.

Maximum Von Mises stress occurs at the foundations at seabed level.

Maximum deflection recorded at harsher sea is (23.36 cm).

Maximum shear stress in legs happens at 25-27 meters from seabed.

It needs a special arrangement to prevent failure.

Foundations with diameters 8, 8.5, 9, 9.5, 10, 10.5, 11 m are suitable to fix the jack up platform on seabed.

The smallest diameter provides good results with less weight and suitable space to join the foundations to jack-up platform legs.

Main Subjects

Mechanical Engineering

Topics

• Dynamics

No. of Pages

176

Table of Contents

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-317120