Features of New High-Strength Steel Materials '550 N/mm2 Class' for Building Framest

JFE Steel developed a new line of high-strength steel products with a lower limit tensile strength of 550 N/mm2 for building frames using its advanced Super-OLAC (on line accelerated cooling)accelerated cooling technology. This product series currently consists of a steel plate, 'HBL385,' circular steel tube, 'P-385,' and square steel tube, 'P Column G385.' These products realize high strength and excellent earthquake resistance while maintaining the weldability of the conventional steel. The results of a test of members using the square tube confirmed that the cumulative ductility factor of 30, which is required in columns, can be sufficiently secured. A rolled H-shape steel, 'HBL-H385,' is also under development. A design trial was carried out to investigate the qualitative advantages and problems with these products. The results showed that it is difficult to guarantee the design criteria necessary to replace the beams in all stories as story drift increases by more than 20% due to reduced stiffness, but replacement of columns presents no problems for practical use. A further expansion of the applicable range is possible if designs are prepared using these products from the initial stage.