For several years, basic research, using slit type test specimens, has been conducted on a concept in weld joints which has been defined as the “coefficient of restraint”. The corelation between this coefficient and the residual stress in weld joints, was determined by applying this concept of coefficient of restraint on actual structures. The xperiments were made in two ways ; (a) on models of solid structures having stiffeners or other similar restraining parts, and (b) by measuring the coefficient of restraint on actual vessels. The results were then compared with the basic theory. It is hoped that the outcome of these experiments will prove to be an important basis for determining the welding sequence for joints that connect one block or unit structure to another.