Damage to concrete structures due to the January 17, 1995, Hyogo-ken Nanbu (Kobe) earthquake

Abstract

A brief history of the detailing changes following different Japanese earthquakes is presented. The design steps for reinforced concrete structures, as prescribed in the 1981 Japanese building code, are described. Observations on the damage and the collapse of reinforced concrete structures caused by the 1995 Hyogo-ken Nanbu earthquake are reported. Failures occurred in older structures built before the improved 1981 code. Deficiencies observed include discontinuities due to the change between composite steel and reinforced concrete construction and reinforced concrete construction in columns, poor detailing of transverse reinforcement in columns, lack of transverse reinforcement in beam–column joints, insufficient amount of vertical and horizontal reinforcement in walls, presence of significant torsional eccentricities, abrupt changes in stiffness over the height of buildings, and the use of "short" columns or "short" beams exhibiting high shear-to-moment ratios. The excellent performance of structures designed using the 1981 Japanese code is described. Key words: earthquake, Kobe, concrete structures, codes, damage, design.