In the Hyougoken-Nanbu Earthquake (1995), the fractural modes of failures were predomination in the damage of steel buildings. In the paper, the transition of fractural modes of steel structural elements from brittle fracture to a ductile fracture was discussed. For building material of steel, the tensile tests and Charpy-impact tests were executed in various temperatures. Finally, full-scale tests of the beam-to-column connection as a representative of structural elements were carried out in three conditions of temperature. Using the nil ductility temperature, an evaluation of failure modes on steel buildings was tried.
