In an attempt to reduce the risk of lamellar tearing during welding of ultr
athick plates, the present study has evaluated the susceptibility to lamell
ar tearing of steel structures in relation to welding stress rather than me
tallurgical properties, and evenutally attempted to determine the optimum g
roove shape and welding procedure by computer simulation based on the finit
e clement method. Based on the simulation, it has been identified that cont
rolling the shape of the deposited weld metal in the anticipated position o
f the occurrence of lamellar tearing is the most favourable method of preve
nting lamellar tearing by minimising welding residual stress and strain. Ow
ing to the difference in weld deposited area, the cooling rate for the part
ial penetration condition is more rapid than for full penetration. Furtherm
ore, in terms of welding residual stress, the full penetration condition is
preferable to the partial penetration condition.