Session: 03-02-01 Fatigue Performance and Testing

Submission Number: 180968

Towards Harmonization of Fatigue Design Documents: A Joint Industry Project Between TWI LTD and DNV 

The established fatigue design documents BS 7608 and DNV RP-C203 are widely used for the fatigue design of welded structures. However, there are notable differences between these documents in a number of areas, specifically, some of the S–N curves, treatment of stress concentrations, thickness effects, residual stresses, and environmental influences. These differences have consequences for designers of new offshore structures.

To address this, a Joint Industry Project (JIP) has been initiated jointly by TWI Ltd and DNV, supported by five sponsor companies from across the offshore engineering sector. The project comprises six work packages: (1) gap analysis of existing standards and development of advanced statistical methods for S–N data interpretation, (2) evaluation of stress concentration and thickness effects, (3) assessment of residual stress influences, (4) consideration of environmental factors, and (5) review of weld improvement techniques and (6) risk-based inspection strategies.

The primary objectives are to systematically identify and quantify the differences between BS 7608 and DNV RP-C203, assess their impact on engineering design, and determine areas where unification is feasible. Where harmonization is currently limited by data or understanding, the project will propose targeted experimental programs to close these knowledge gaps. This paper presents the scope, methodology, and preliminary findings of the JIP, highlighting the pathway toward a unified fatigue design framework which will benefit the offshore industry.

Presenting Author: Carol Johnston TWI Ltd

Presenting Author Biography: Dr Carol Johnston gained her degree and PhD in Materials Science from Cambridge University. She joined the Fatigue Section at TWI in 2009, developing her knowledge of fatigue of welded joints and resonance testing and gradually taking over the leadership of the TWI’s resonance testing business stream. In addition to her expertise in the fatigue performance of girth welds, mechanically lined pipe and subsea connectors, and resonance fatigue testing, Carol has run projects on many other topics related to the structural integrity and fatigue performance of welds and bolted connections.

Authors:

Carol Johnston TWI Ltd
Agnes Marie Horn DNV