This paper is concerned with a computer-aided design system for education in steel structural design. Beginners in the structural design field have to study hard and take the long term to retrieve their skill of design. It is said that their effort should take a few years to achieve it. However, Japan is going through the age of declining birthrate and a growing proportion of elderly people. The new system presented here takes structural design of steel sub-beams supporting concrete slab to demonstrate the concept of multi-acquisition of solutions.
At hybrid joints of steel girders using bolted and welded joints, it is necessary to implement erection pieces as restrainers of welded joints and to remove them after welding. To enable the connection without the erection pieces, we proposed a new connection method of hybrid joints, in which we use the bolted connections of longitudinal ribs as the restrainers by tightening the bolts before welding. To establish a procedure of the method, we carried out trial execution tests of hybrid joints. As a result, it was clarified that the bolted joints slipped at the time of untightening the bolts, while they did not slip at the welding stage. After the slip, the damage of the friction surfaces was localized to small regions around the remaining bolts.