Post-tensioned (PT) self-centering moment frames have been developed as an altative to typical moment-resisting frames (MRFs) for earthquake resistance.When a PT frame deforms laterally,gaps between the beams and columns open.However,the gaps are constrained by the columns and the slab in a real PT selfcentering building frame.This paper presents a methodology for evaluating the column restraint and beam compression force based on the column deformation and gap openings at all stories.The method is verified by cyclic tests of a full-scale,two-bay by one-story PT frame.Moreover,a sliding slab is proposed to minimize restraints on the expansion of the PT frame.Shaking table tests were conducted on a reduced-scale,two-by-two bay one-story specimen,which comprises one PT frame and two gravitational frames.The PT frame and gravitational frames are self-centering throughout the tests,responding in phase with only minor differences in peak drifts caused by expansion of the PT frame.When the specimen is excited by a simulation of the 1999 Chi-Chi earthquake with a peak ground acceleration of 1.87 g,the maximum interstory drift and the residual drift are 7.2％ and 0.01％,respectively.