Fifty Years of Severe Earthquake Experiences in Japan and the Next Direction of Steel Structures in the World

Steel is a superior structural material due to its strength and ductility. These properties are advantageous especially for seismic resistant buildings. Masonry wall structures are vulnerable to earthquakes with their heavy weight and brittleness. Having a lower fire resistant nature is critical for wooden structures. For reinforced concrete (RC) structures, it is difficult to equip seismic energy dissipating systems. The RC structures can absorb the seismic energy with their plastic deformation with cracks; however, residents do not feel at ease with cracked RC buildings by large earthquakes and do not wish for such cracks to remain inside. In spite of the superior material properties of steel, extensive damage has been observed after large earthquakes over the past 50 years. Damage tolerant structures were proposed with the development of eccentric brace frames and buckling restrained braces (BRBs) in 1970 and 1987, respectively. Nowadays, many passively controlled steel buildings using BRBs or other damping devices have been constructed. A brief history about the innovation of damage tolerant structures and recent applications in Japan are introduced.