The Japanese Building Standard Law and a series of steels for earthquake-resistant building structures
This contribution refers to the Building Standard Law in Japan and by focusing especially on the part which is related to seismic forces, shows how to protect humans and property (in Japan) from earthquake disasters. In 1981, the Law was amended to introduce plastic design into architecture. In order to enhance the ability of the new seismic proof structural design method, a new series of steels was developed and manufactured in 1994. Material damage induced by repeated earthquakes is investigated in this paper. The newly produced pre-damaged SN490B steel (one of the new steels) is tested and evaluated under dynamic tension. The pre-damage is introduced by pre-fatiguing or pre-straining. Compared with SM490A steel (a conventional steel), the remaining mechanical properties of the SN490B steel resemble those of SM490A even under dynamic tension. However, once plastic deformation has developed in the SN490B steel, it loses the capability of accepting large deformation when used in structural members. Tests suggested that, once the structural building has suffered plastic deformation, the building components will not comply with the new seismic proof design method. In case of such a condition, the components fabricated from these new steels should be either reinforced, replaced or rebuilt.