Ryu Kasai

An estimation of factors influencing residual stress characteristics of fillet welded lap joints

Abstract The residual stress behaviours in fillet welded lap joints of sheet metal have been researched in a systematic testing procedure with varied steel types, steel thicknesses and welding wires having different transformation points. Consequently, under the simulated fabrication welding conditions (with a constant amount of deposited metal), the transverse residual stress at the weld toe, which is deemed critical in fatigue strength, has been found almost invariable to a change in steel type and thickness, but it has been clarified to become compressive to a greater extent as the wire’s transformation point is lower. Moreover, as for the residual stress inside the weld metal, the compressive residual stress area has been found to expand as the welding wire’s transformation point reduces, from the results of the thermo-elastic-plastic analysis.

Improvement of the deformation capacity of the column-to-beam joint by the reinforce welding method around the scallop bottom

Abstract Improvement of deformation capacity for a column-to-beam joint is an important theme for improving the earthquake-resistance performance of building structures. One of the causes of decreasing deformation capacity is the existence of stress concentration against the beam flange by the scallop (access hole). The non-scallop method is generally recommended to improve this problem, but it has a large disadvantage in that it is not able to apply to the on-site joint process. The reinforce welding method around the scallop bottom has been developed to be able to apply to an on-site joint and obtain better performance than the non-scallop method. The improved mechanism is a combination of: (1) decreasing the stress concentration; (2) increasing effective thickness; and (3) increasing total length of the breaking line. The deformation capacity by the reinforce welding method around the scallop bottom is a maximum 3.2 times that for the conventional scallop method in the reverse repeating bend test using an actual structure with a beam flange of 19 mm thickness and 490 N mm−2 class steel. This improving effect is better than the non-scallop method.