SEISMIC DESIGN AND PERFORMANCE OF HINGED TRUSS FRAME STRUCTURES

Beams at certain stories of a reasonably-designed frame may yield first due to a uniformly-distributed seismic force, which causes an increase in the drift concentration factor (DCF). It is difficult for a frame to exhibit a complete beam hinge mechanism, which requires that the plastic hinges appear at the beam-ends of all stories and the column base. To reduce the inter-story damage concentration and increase the lateral stiffness of common steel frames, by installing zipper columns and braces in the frame, a hinged truss frame structure is proposed to control the lateral displacement and its distribution of the frame. The elastic DCFs of frames are derived and used as the DCF target values of the hinged truss frames. Thus, the reasonable stiffness ratio of the hinged truss to the frame is determined. A seismic design process based on the DCF is presented and the design example shows the expected displacement and DCF performance target. The seismic performance of a bare frame, a rocking wall frame and a hinged truss frame is compared. The results show that the hinged truss can improve the lateral stiffness of the frame, change the plastic hinge distribution mode of the frame from incomplete to complete beam hinge mechanism and make the frame inter-story drift ratio and shear to distribute uniformly. In comparison to the rocking wall frame, the hinged truss frame shows larger lateral stiffness and similar lateral deformation mode.