Fundamental Study on Seismic Response of Steel Moment Frames Sustaining Beam-Hinging Mechanism

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This research aims at developing a numerical analysis program, which precisely simulates dynamic behaviors of steel moment frames and at examining of seismic response derived from analytical results. The frames are weak-beam type frames, whose beams are weaker than their columns with respect to full plastic bending moment.The frame analysis program, which the author already has been developed, deals with not only joint panels but also column-bases for accuracy of trace behaviors of pure steel frames. For a further refinement of the program, a new function was implemented into the program, which makes the program be able to deal with composite action of beams and reinforced concrete slabs. The analytical main steel frame consists of one-dimensional finite elements. Moreover, the reinforced concrete slabs settled en the beams were modeled with the consistency of deformation and stress-strain relationship covering over deteriorating region.A numerical work was conducted using the new developed program to examine the composite effect of R/C slabs on the behaviors of over-all frames comparing results of pure or naked steel frames with those of frames with R/C slabs. As a result, followings were withdrawn from the numerical study; 1) The basic period as eigen-value of naked frames is longer than that of frames with R/C slabs from 5 to 10 percent. 2) The maximum story drift angle of naked frames is as large as that of frames with R/C slabs from 1.0 to 1.5 times. 3) As for the maximum story drift angle of frame, the legacy method, which is called as the plastic-hinge method gives rather accurate results in case where moment of inertia of beams are suitably increased.