This paper investigates the relationship between the toughness of submerged arc welding and the plastic deformation capacity of field weld type moment connection containing pre-assembled type build-up H-shaped beam. Cyclic loading tests and finite element method analyses were conducted, which showed that the premature brittle fracture was occurred in the connections with low toughness of the welding or constructed by field weld type. From the results, a mechanism of brittle fracture of beam flange joint were revealed.
