This International Standard specifies qualities for seismic-purpose structural steels. This International Standard applies to steel plates with thicknesses of 6 mm or over and up to 125 mm, wide flats and hot-rolled sections, which are used in the as-delivered condition and normally intended for bolted, riveted or welded structures 1). It does not include the following steels, certain of which are covered by other International Standards, namely: ? structural steels (ISO 630); ? steels for general engineering purposes (ISO 1052); ? high-yield-strength flat steel products (ISO 4950-1, ISO 4950-2 and ISO 4950-3); ? high-yield-strength steel bars and sections (ISO 4951-1, ISO 4951-2 and ISO 4951-3); ? structural steels with improved atmospheric corrosion resistance (ISO 4952); ? high-yield-strength steel plates and wide flats for cold forming (ISO 6930-1 and ISO 6930-2).