Decoupling the strength and drift criteria in steel moment-resisting frames

Superior ductility of moment-resisting frames allows for high response modification factors, therefore design for smaller earthquake loads. In contrast, to limit the lateral drift, the cross-sectional dimensions of the beams and columns are increased, which deactivates the benefits of the achieved high response modification factor. The linked beam frame system is proposed in this paper to decouple the strength and drift criteria. The link elements are added between the beams of two adjacent stories in spans where allowed architecturally to control the drift while they also increase the potential sources of energy dissipation. The design procedure is straightforward and prevents the trial and error analysis required for conventional moment-resisting frames. The effect of the links on the lateral stiffness of the structure is estimated, and prototype buildings of five, 10, and 15 stories are investigated using linear and nonlinear analyses. A comparison of the results between the proposed system and the conventional method indicates that in addition to simplification of the design procedure, saving of about 10% to 15% in steel material of each lateral load resisting frame is achieved.