This paper investigates the toughness of submerged arc weld metal included in preassembled type build-up H-shaped beam which prevent the premature brittle fracture of moment connection. Deformation capacities before fracture of many kind of moment connections containing rolled H-shaped section beam are analyzed statistically and the indices of the deformation capacity are defined to evaluate the toughness. The relationship between the deformation capacity of the moment connection containing pre-assembled type build-up H-shaped beam and the toughness are investigated considering with the destruction property and the effect of loading protocol using the indices, which reveals the necessary value of the toughness to prevent the premature brittle fracture.
