島田 侑子

<title>Abstract</title> Submerged arc welding, which is generally used for the corner joint of box-section columns, is a welding process with a high heat input. The influence on the strength and toughness of the heat-affected zone is an important concern, especially when used with a high-performance steel that may be more susceptible to heat input. The ductility of the welded corner joint is one of the important factors to ensure safety against external forces, such as during severe earthquakes. In this study, a series of material and cyclic loading tests of the corner joint comprising SA440C high-performance steel fabricated by submerged arc welding were conducted. The experimental results indicated that the welded corner joint comprising SA440C steel is ductile enough to dissipate input energy caused by the strong ground motion from an earthquake.

The aim of this study was to validate the reinforcement method used for joints connecting a steel roof and a reinforced concrete (RC) frame in existing buildings based on a series of cyclic loading tests. Three reinforcement methods were investigated in the study: one using a steel jacket and high-strength steel rods (Type-1), another using a steel jacket and post-installed adhesive anchors (Type-2), and a third using a steel plate and post-installed adhesive anchors (Type-3). The results obtained show that the Type-1 method is most effective in increasing force, because shear force can be transferred from the RC frame to the steel roof; thus, a steel jacket can support the entire top of the RC column and integrate the roof joints into the RC frame. The Type-2 and Type-3 methods, however, are not effective in the reinforcement of RC columns because shear force cannot be transferred, and concrete failure occurred easily.