Seismic design and shake table tests of a steel post-tensioned self-centering moment frame with a slab accommodating frame expansion

Abstract

Post-tensioned (PT) self-centering moment frames were developed as an alternative to welded momentresisting frames (MRFs). Lateral deformation of a PT frame opens gaps between beams and columns. The use of a composite slab in welded MRFs limits the opening of gaps at the beam-to-column interfaces but cannot be adopted in PT self-centering frames. In this study, a sliding slab is used to minimize restraints to the expansion of the PT frame. A composite slab is rigidly connected to the beams in a single bay of the PT frame. A sliding device is installed between the floor beams and the beams in other bays, wherever the slab is allowed to slide. Many shaking table tests were conducted on a reduced-scale, two-by-two bay one-story specimen, which comprised one PT frame and two gravitational frames (GFs). The PT frame and GFs were self-centering throughout the tests, responding in phase with only minor differences in peak drifts that were caused by the expansion of the PT frame. When the specimen was excited by the 1999 Chi-Chi earthquake with a peak ground acceleration of 1.87g, the maximum interstory drift was 7.2% and the maximum lateral force was 270 kN, equal to 2.2 times the yield force of the specimen. Buckling of the beam bottom flange was observed near the column face, and the initial post-tensioning force in the columns and beams decreased by 50 and 22%, respectively. However, the specimen remained self-centering and its residual drift was 0.01%. Figure 1. (a) PT connection and (b) flag-shaped hysteretic behavior.of an MRF with PT connections exceeds the performance of an MRF with typical welded connections [12,13].Although the newly developed PT connection provides satisfactory cyclic performance, Kim and Christopoulos [13] and Garlock et al. [14,15] raised the issue of how columns and slabs restrainted PT frame expansion. Gap opening at the beam-to-column interfaces causes an expansion of the PT frame. The column and slab restraints that oppose the frame expansion affect the compression force in the PT beam. Kim and Christopoulos [13] suggested an approximate approach to estimate the restraint, which is appropriate in cases where a more concentrated response occurs at a single floor alone and overly conservative in cases where the structure responds in its fundamental mode. For a PT frame that responds in its fundamental mode, Chou and Chen [16] proposed a method for evaluating the restraint that considered the continuity and boundary conditions of the column. The method requires a structural analysis of the column in a deformed configuration and equations that are derived from the compatibility of deformation of beams, strands, and columns.When gaps open at the beam-to-column interfaces, the concrete slab, if it does not open near the columns, restrains frame expansion, affecting the self-centering [17]. Garlock et al. [14,15] and King [10] suggested that the collector beams or bays transfer the inertial force into the PT frame and accommodate PT frame expansion. Kim and Christopoulos [13] proposed detail...

Seismic tests of post-tensioned self-centering building frames with column and slab restraints

“…Kim and Christopoulos [11] suggested an approximation approach to estimate the column restraint, which is only appropriate for cases in which a more concentrated response occurs at a single floor alone and is overly conservative for cases in which the structure responds in its fundamental mode. For a PT frame that responds in its fundamental mode, Chou and Chen [13] proposed a method for evaluating the restraint that considers the continuity and boundary conditions of the column.…”

“…The method is validated by cyclic tests of a full-scale, twobay by one-story PT frame, representing a substructure of a three-story frame. Secondly, shaking table tests are conducted on a reduced scale, two-by-two bay one-story PT building structure with a slab accommodating the expansion of the PT frame under earthquake scenarios [13].…”

Self-Centering Seismic Lateral Force Resisting Systems: High Performance Structures for the City of Tomorrow

“…Large-scale frame tests of steel self-centering moment resisting frames [41,86,92] showed considerably better seismic performance compared to conventional moment resisting frames. Steel self-centering moment resisting frames are generally expected to remain undamaged during the DBE, allowing immediate occupancy of the structure and to prevent collapse under the maximum considered earthquake (MCE) [86].…”

“…A type of post-tensioned rocking connection detail [75] is proposed in which the connection is permitted to rock only about beam bottom flange while the contact of the beam top flange with the column is preserved at all time. Other diaphragm and gravity beam connection details have also been proposed [85,92,104] to address the frame expansion issue. (a) (b) Figure 11.…”

High Performance Damage‐Resistant Seismic Resistant Structural Systems for Sustainable and Resilient City: A Review

“…It is proposed that the beam-column connection can rock at the beam bottom flange while the beam top flange with the column is preserved all the time [207]. A sliding slab is used to minimize restraints on the expansion of the PT frame, in which a composite slab is rigidly connected to the beams in a single bay of the PT frame, and a sliding device is installed between the floor beams and the beams in other bays such that the slab is allowed to slide [208,209].…”