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Reliable Fatigue Design of Welded Joints following the Eurocode-3 Conceptual Analysis and Possible Improvements G. Coussan (1) , J-M. Nianga (2) and N. Recho (3) (1) & (2) HEI, 13 rue de toul; 59046 Lille cedex, France (3) EPF, 3bis rue lakanal, 92330 Sceaux, France « ESIS TC2 Oxford 2012 », 4th of April 2012, COUSSAN.G, [email protected] page 1 of 13

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Reliable Fatigue Design of Welded Joints following the Eurocode-3

Conceptual Analysis and Possible Improvements

G. Coussan (1) , J-M. Nianga (2) and N. Recho (3)

(1) & (2) HEI, 13 rue de toul; 59046 Lille cedex, France

(3) EPF, 3bis rue lakanal, 92330 Sceaux, France

« ESIS TC2 Oxford 2012 », 4th of April 2012, COUSSAN.G, [email protected] page 1 of 13

Plan => Introduction => Numerical Simulation =>

Reliability analysis => Conclusion

Plan

• Introduction

• Parameters choice and mesh box

• Eurocode problem

• Simulation results and fatigue design

• Geometrical stress equation

• Reliability approach

• Conclusion

« ESIS TC2 Oxford 2012 », 4th of April 2012, COUSSAN.G, [email protected] page 2 of 13

Plan => Introduction => Numerical Simulation =>

Reliability analysis => Conclusion

« ESIS TC2 Oxford 2012 », 4th of April 2012, COUSSAN.G, [email protected] page 3 of 13

Geometrical stress determination according to eurocode 3. The geometrical stress corresponds to the value obtained by extrapolation at the weld toe of a straight line (the dot line on the figure) formed by the two stress values crossing the stress curve at the points of abscissa 0,4T and 1,0T.

Plan => Introduction => Numerical Simulation =>

Reliability analysis => Conclusion

« ESIS TC2 Oxford 2012 », 4th of April 2012, COUSSAN.G, [email protected] page 4 of 13

Detail class and SN curve extract from Eurocode 3 (part 1-9). Thoses curves are used to determine the fatigue lifetime with the estimated stress level.

Plan => Introduction => Numerical Simulation =>

Reliability analysis => Conclusion

« ESIS TC2 Oxford 2012 », 4th of April 2012, COUSSAN.G, [email protected] page 5 of 13

Parameters choice (T is the plate thickness, Rc is the weld toe radius, e is the weld thickness and θ is the weld angle) and mesh-box.

Plan => Introduction => Numerical Simulation =>

Reliability analysis => Conclusion

« ESIS TC2 Oxford 2012 », 4th of April 2012, COUSSAN.G, [email protected] page 6 of 13

Extracted results from one of the simulations (Rc = 0,5mm ; θ = 60° ; e = 14mm ; pure traction ) showing the problem with eurocode definition of geometrical stress, the Kt value beeing below 1.

Plan => Introduction => Numerical Simulation =>

Reliability analysis => Conclusion

« ESIS TC2 Oxford 2012 », 4th of April 2012, COUSSAN.G, [email protected] page 7 of 13

New method to determine the geometrical stress relie on a 2% stress gap between concave and convex configuration.

Plan => Introduction => Numerical Simulation =>

Reliability analysis => Conclusion

« ESIS TC2 Oxford 2012 », 4th of April 2012, COUSSAN.G, [email protected] page 8 of 13

Fatigue design to study the parameters effect on the new geometrical stress.

Parameters System answers

Rc (mm) theta (°) e (mm) loading (% moment)

X1 (mm) Sigma X1 (Mpa) Kt

Configuration 1 0,5 30 8 0 0,37 86,6 1,73

Configuration 2 0,5 30 14 50 0,37 79,8 1,60

Configuration 3 0,5 60 8 50 1,23 67,0 1,34

Configuration 4 0,5 60 14 0 1,30 72,7 1,45

Configuration 5 5 30 8 50 2,89 54,4 1,09

Configuration 6 5 30 14 0 3,02 55,7 1,11

Configuration 7 5 60 8 0 5,27 52,5 1,05

Configuration 8 5 60 14 50 5,17 51,7 1,03

Configuration 9 0,5 30 8 50 0,37 79,8 1,60

Configuration 10 0,5 30 14 0 0,37 86,7 1,73

Configuration 11 0,5 60 8 0 1,25 72,5 1,45

Configuration 12 0,5 60 14 50 1,25 67,1 1,34

Configuration 13 5 30 8 0 3,00 56,0 1,12

Configuration 14 5 30 14 50 2,90 54,3 1,09

Configuration 15 5 60 8 50 5,11 52,0 1,04

Configuration 16 5 60 14 0 5,37 52,0 1,04

Medium configuration 2,75 45 11 25 3,19 55,9 1,12

Plan => Introduction => Numerical Simulation =>

Reliability analysis => Conclusion

« ESIS TC2 Oxford 2012 », 4th of April 2012, COUSSAN.G, [email protected] page 9 of 13

Direct parameters effect on Kt.

Plan => Introduction => Numerical Simulation =>

Reliability analysis => Conclusion

« ESIS TC2 Oxford 2012 », 4th of April 2012, COUSSAN.G, [email protected] page 10 of 13

Plan => Introduction => Numerical Simulation =>

Reliability analysis => Conclusion

« ESIS TC2 Oxford 2012 », 4th of April 2012, COUSSAN.G, [email protected] page 11 of 13

Equation that allows a prediction of the new geometrical stress.

Plan => Introduction => Numerical Simulation =>

Reliability analysis => Conclusion

« ESIS TC2 Oxford 2012 », 4th of April 2012, COUSSAN.G, [email protected] page 12 of 13

Plan => Introduction => Numerical Simulation =>

Reliability analysis => Conclusion

« ESIS TC2 Oxford 2012 », 4th of April 2012, COUSSAN.G, [email protected] page 13 of 13

Conclusion: -New method to determine geometrical stress with reliability analysis. -Better consideration of geometrical configuration. -Fatigue design possibly without numerical simulation for the geometrical stress determination.

Studies to come: -Taking into account non-linear effects. -Feeding reliability analysis with experimental data. Used software: CAST3M, Abaqus, Statgraphics, Excel.

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