TY - JOUR

T1 - New proposal to express notch stress approach results by equivalent SCFs

AU - Schaumann, P.

AU - Schürmann, K.

N1 - Funding Information: The presented results are developed within the German FOSTA joint research project ‘FATInWeld’ supported via AiF ( IGF 19104N ) within the programme for promoting the Industrial Collective Research (IGF) of the German Ministry of Economic Affairs and Energy (BMWi), based on a resolution of the German Parliament. The authors express their deep gratitude for the financial support received from the BMWi, the AiF and the FOSTA as well as for the outstanding cooperation with the research partner BAM.

PY - 2019/2

Y1 - 2019/2

N2 - For the fatigue design of welded structures, such as jacket substructures for offshore wind energy turbines, the structural stress approach is state of the art. Standards and guidelines also allow the application of the notch stress approach for complex welded components, weld roots, or to consider the advantages of the real weld geometry if measured or after grinding within the fatigue design. Since the theoretical background as well as the application of both approaches differs widely, it is not possible to directly integrate the fatigue notch factor Kf according to the notch stress approach into the design formalism of the welded structures based on the structural stress approach. Therefore, this paper derives a methodology to transform the elastic fatigue notch factor Kf into an equivalent stress concentration factor. By applying the introduced concept design engineers are able to selectively combine the advantages of both approaches without adapting the approved software tools to perform the fatigue design of complete welded structures. Furthermore, the presented concept of the equivalent stress concentration factor is an effective tool to perform a direct comparison of the relative fatigue resistance according to both approaches – structural stress approach and notch stress approach – on structural stress concentration level rather than on the level of damages or lifetime. This opportunity of comparison is applied on a tubular X-joint of a jacket substructure. The computed stress concentration factors are in good accordance between both approaches which is similar to the lifetime based results given in literature for application of both approaches on tubular K- and Y-joints.

AB - For the fatigue design of welded structures, such as jacket substructures for offshore wind energy turbines, the structural stress approach is state of the art. Standards and guidelines also allow the application of the notch stress approach for complex welded components, weld roots, or to consider the advantages of the real weld geometry if measured or after grinding within the fatigue design. Since the theoretical background as well as the application of both approaches differs widely, it is not possible to directly integrate the fatigue notch factor Kf according to the notch stress approach into the design formalism of the welded structures based on the structural stress approach. Therefore, this paper derives a methodology to transform the elastic fatigue notch factor Kf into an equivalent stress concentration factor. By applying the introduced concept design engineers are able to selectively combine the advantages of both approaches without adapting the approved software tools to perform the fatigue design of complete welded structures. Furthermore, the presented concept of the equivalent stress concentration factor is an effective tool to perform a direct comparison of the relative fatigue resistance according to both approaches – structural stress approach and notch stress approach – on structural stress concentration level rather than on the level of damages or lifetime. This opportunity of comparison is applied on a tubular X-joint of a jacket substructure. The computed stress concentration factors are in good accordance between both approaches which is similar to the lifetime based results given in literature for application of both approaches on tubular K- and Y-joints.

KW - Equivalent SCF

KW - Notch stress approach

KW - Structural stress approach

KW - Tubular X-joint

KW - Welded steel joints

UR - http://www.scopus.com/inward/record.url?scp=85054155934&partnerID=8YFLogxK

U2 - 10.1016/j.ijfatigue.2018.09.009

DO - 10.1016/j.ijfatigue.2018.09.009

M3 - Article

AN - SCOPUS:85054155934

VL - 119

SP - 11

EP - 19

JO - International Journal of Fatigue

JF - International Journal of Fatigue

SN - 0142-1123

ER -