Welding is the most convenient method for fabricating steel materials to build ships and offshore structures. However, welding using high heat processes inevitably produces welding displacements on welded structures. To mitigate these, heavy industries introduce various welding techniques such as back-step welding and skip-step welding. These techniques effect on the change of the distribution of high heat on welded structures, leading to a reduction of welding displacements. In the present study, various cases using different and newly introduced welding techniques are numerically simulated to ascertain the most efficient technique to minimize welding displacements. A numerical simulation using a finite element method based on the inherent strain, interface element and multi-point constraint function is introduced herein. Based on several simulation results, the optimal welding technique for minimizing welding displacements to build a general ship grillage structure is finally proposed.

Abstract
1. Introduction
2. Numerical approach for welding simulation
    2.1 Inherent deformation and inherent strain
    2.2 Interface element
    2.3 Multi-point constraint function
3. Analysis model
4. Efficient welding technique
    4.1 Results and discussion of the general plane plate
    4.2 Results and discussion of the general ship grillagestructure
5. Conclusion
References

• Donghan Woo(Department of Transport and Environmental System, Hiroshima University)