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Chou C.-C.,National Taiwan University | Chou C.-C.,National Center for Research on Earthquake Engineering | Chen J.-H.,Federal Engineering Consultant Inc.
Journal of Constructional Steel Research | Year: 2011

A floor slab constructed in conventional moment-resisting frames (MRFs) limits opening of gaps at the beam-to-column interfaces, causing losses of self-centering capability and preventing its use in steel post-tensioned (PT) moment frames. This work presents two novel slab schemes to reduce the restraints on the seismic responses of a PT frame. The first scheme uses a slab in typical MRFs with a modification so that near the connection, the metal deck is discontinuous and the longitudinal bar in the deck is debonded from concrete to minimize slab restraints. The second scheme uses truss elements to connect the slab and beams in only one bay (rigid bay) of the PT frame for transferring inertial forces from the floor to the frame. The sliding device is provided at one end of floor beams transverse to the PT frame, where sliding of the slab is expected. The cyclic behaviors of the bare connection and the connection with the first slab scheme are also evaluated by testing four connections. Additionally, how the rigid bay affects the cyclic behavior of the frame, distribution of column shear, beam axial force variation, and gap opening response near the beam-to-column interface is evaluated by conducting frame subassembly tests. The test results demonstrate that (1) the PT frame with any of two slab schemes develops large deformation capacities with small residual deformations, and (2) the column shear and beam axial force can be estimated based on the proposed method. © 2011 Elsevier Ltd. All rights reserved.

Chou C.-C.,National Taiwan University | Chen J.-H.,Federal Engineering Consultant Inc.
International Journal of Structural Engineering | Year: 2012

A three-story frame was designed for earthquake resistance by using post-tensioned (PT) columns and beams. Two interior connections, representing the first floor column and beam sizes, were tested under cyclic loading to evaluate the effects of energy dissipation and PT load and on the seismic behaviour. A full-scale one-story two-bay specimen frame, which was a substructure of the three-story PT building, was then built and tested. This paper presents experimental results of the connections and the frame and analytical simulations for the frame subassembly. Time-history analyses of the three-story PT building subjected to the design basis earthquake (DBE) and the maximum considered earthquake (MCE) were conducted to investigate seismic demands of the proposed frame. These tests confirmed the self-centring responses of the connections and the frame. Inelastic time history analyses of the three-story prototype building showed that the proposed frame system can achieve seismic demands under MCE level ground motions. Copyright © 2012 Inderscience Enterprises Ltd.

Lim E.,Bandung Institute of Technology | Hwang S.-J.,National Taiwan University | Cheng C.-H.,Federal Engineering Consultant Inc. | Lin P.-Y.,Consulting Inc.
ACI Structural Journal | Year: 2016

The seismic performance of intermediate clear span-depth ratio (2.0 ≤ ℓn/h ≤ 4.0) coupling beams with hybrid layout were evaluated in this study. By combining the conventional ductile beam detailing and the benefit of the presence of diagonal bars, this study shows that the hybrid layout may serve as one of the possible alternatives to ease construction difficulty. Test results found out that, at the maximum considered earthquake (MCE) level, the shear strength of a coupling beam was governed by the crushing of concrete strut in the plastic hinge regions and yielding of diagonal bars. To allow a full development of concrete strut capacity and to maintain integrity of core concrete, sufficient internal support must be provided by the transverse reinforcement. Using the proposed shear-strength equation, a more rational approach can be adopted to determine the appropriate reinforcement layout and the efficient amount of diagonal bars for a coupling beam with 2.0 ≤ ℓn/h ≤ 4.0. © Copyright 2016. American Concrete Institute. All rights reserved.

Chou C.-C.,National Taiwan University | Chou C.-C.,National Center for Research on Earthquake Engineering | Chen J.-H.,Federal Engineering Consultant Inc.
Engineering Structures | Year: 2011

The first generation for the post-tensioned (PT) self-centering (SC) system, which incorporates the PT technology to beam-to-column connections, exhibits good seismic performance with small residual deformations except for the first floor. Instead of using the fixed column base, the column PT to the base affects the seismic performance of frames, especially for residual deformations. Recently, the seismic response of a SC frame subassembly, which applied the PT technology to the connection and column base, was verified in shake table tests. In this paper, a three-dimensional analytical model with rotational springs in the PT connection and PT column base was introduced to capture shake table test results of the frame subassembly. The same modeling approach was adopted to one MRF and three SC frames to study the effects of column bases on the seismic responses of frames under the design-based and maximum-considered earthquakes. The monotonic, cyclic pushover, and time-history analyses were conducted for these frames. Analytical results showed that (1) the residual drift of the first floor could be significantly minimized by using the PT column base but the maximum interstory drift in the SC frame increased with decreasing fixity at the column base, (2) the largest maximum interstory drifts of the SC frames were larger than those of the MRF due to the low-to-medium structural period and high yield strength, and (3) the SC frame with the PT column base effectively decreased column restraining forces to the first floor compared to that with the fixed column base. © 2011 Elsevier Ltd.

Chou C.-C.,University of Taipei | Chen J.-H.,Federal Engineering Consultant Inc.
Frontiers of Architecture and Civil Engineering in China | Year: 2011

Post-tensioned (PT) self-centering moment frames have been developed as an alternative 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 self-centering 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. © 2011 Higher Education Press and Springer-Verlag Berlin Heidelberg.

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