Mitigating local buckling of post-tensioned connections in steel self-centering moment resisting frames
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Self-centering moment resisting frames (SC-MRF) employ post-tensioned (PT) beam-to-column connections for achieving large drifts while maintaining elastic behavior. The PT bars develop large tension forces as the connection rocks open, pivoting about the end of one of the beam’s flanges. This induces a large compression force in the flange, making it susceptible to beam local buckling. The buckling, in turn, shortens the beam and reduces the PT forces, jeopardizing the frame’s moment capacity and making it more vulnerable to collapse. The SC-MRF design procedure developed by Garlock  used strain limits to prevent buckling. Chou et al.  later used the same concept but modified the limiting strain value. The current experimental data demonstrates that the critical strains for buckling are dependent on the flange width-to-thickness ratio, b/t. Therefore it is recommended that the design procedure should include a beam width-to-thickness limit.