Seismic Behavior of Steel Moment Frames with Reduced Beam Sections

After Northridge earthquake reduced beam sections were suggested to improve connections performance. A new detail has been evaluated for reduced beam sections that includes a combination of two previously investigated models; reduced web section and accordion web section. According to comparison with other models through finite element analysis, it was found that the stresses and plastic strains have been more effectively reduced in the beam to column connection region of the combined detail and up to 9%. Increase in plastic rotation capacity may be achieved without a noticeable loss in strength. According to performed nonlinear static analyses results for well-designed 5, 10 and 15 story steel buildings with special moment resistant frame system, the amount of plastic drift capacity using the reduced beam sections slightly increases and this increase is more in connections with accordion web and accordion web together with reduced web sections respectively. Pushover curves indicate that the reduced beam sections has little effect on the linear part of the curves but increasing drifts, added strength is reduced. The rate of decrease for two connections with accordion web sections and accordion web with reduced web is more. Average rates of behavior factors 11.38 and 11.73 and 11.88 have respectively been obtained for moment resistant frames with reduced beam section and accordion web sections and accordion web with reduced web sections. It can be said that the average rates of behavior factor for frames that are designed based on the behavior factor of 8 has been considerably increased.