Dai-Ichi building

Office building
Osaka, Japan

The construction method specially developed for this high-rise building was a unique structural system with large columns and long-span transfer girders.

Because the building is separated into two distinct structures, lower and upper, it was possible to design the lower part without considering loads from the upper part. A quenched and tempered HSS plate SM570 Q (yield strength 430 N/mm2 and carbon equivalent 0.42%) was used for the large welded box section columns, each measuring 2 by 3 meters. Their maximum wall thickness was 80 millimeters. All column-to-column connections and column-to-beam connections were field welded.

The four large columns, about 30 meters high, support the 45 meter transfer girders and carry large concentrated forces. These HSS columns are designed to remain in the elastic range while resisting severe earthquake oscillations. The upper structure is designed to do the same in the elasto-plastic state.

In the Dai-Ichi Seimei Building the merits of High Strength Steel were as follows:
  • In columns required to support large forces, HSS permitted thinner sections
  • Smaller columns provided more available floor space.
  • Thinner steel was advantageous in the cost of welding and erection