1.                  Background

 

The failure of joints in the offshore platforms is primarily due to fatigue cracks. Stress concentration due to geometry is a main factor influencing the fatigue failure of these joints. Most of the joints of tubular members are, in general, subjected to large local bending stresses in the tube walls around the welded portions. Invariably cracks are observed in these portions.

The test results of tubular T- joint subjected to cyclic loading will be discussed in this project. The goal of this investigation is to study the influence of geometrical stress concentration on the fatigue behaviour of T-joints. A T-joint consists of a large tube, the chord, and smaller tube, the brace, welded at right angles to the chord wall. The T-joints were selected because of their simplest configuration. Further, the chord walls of T-joints have to sustain severe stress concentration which is typical in the tubular joints.

Offshore structures are subjected to maximum loading by cyclic wave forces during the storm. Thus, the number of cycles of peak load which the structure has to withstand in its service period is limited.

 

2.                  Research Capability

 

During my bachelor degree in Mechanical Engineering I achieved good knowledge related to Structure Mechanics. In my master degree I got relevant information about Structural analysis and Fatigue Assessment. Also, I had an opportunity to work with ANSYS software which will be very helpful conducting this study.

 

 

 

3.                  Aims and Objectives of Project

 

Aim: The aim of this project is to simulate the behaviour of a joint in a jacket structure subjected to environmental forces.

 

Objective: The objective of this project is to study the influence of geometrical stress concentration on the fatigue behaviour of T-joints

 

4.                  Methodology

 

A tubular T-joint will be modelled using ANSYS 13.0 software. The wave loading will be calculated according to DNV regulations and then applied on FE model. A non-linear analysis will be carried out in order to assess the stress concentration due to the cyclic loading.

 

5.                  Work packages

 

WP1:    Literature Review

• Undertake a literature search in the relevant subject areas.
• Identify key texts, including books, journal papers, conference papers and web sites.
• Prepare an overview of the present state of knowledge in the subject area, including a summary of key texts, and reference list with bibliographic details.
• Deliverable: Literature review document.

 

WP2:  Modelling T-joint using FEM

 

WP3:  Wave loading calculations and application on the FE model

 

WP4:  Non-linear analysis and results assessment

 

WP5:  Write up report

• Establish format of Report document and set up templates on word processor.
• Review all notes, test results, analyses and tentative conclusions of project work.
• Formally write up majority of project work.
• Finalise conclusions and write Introduction and Conclusion.
• Print off report, collate with appendices and arrange for binding of report.
• Prepare for presentation other items for submission (such as a disk with software, or technical drawings)
• Deliverable: Bound report (two copies) together with accompanying material