Influence of Vertical Ground Shaking on Horizontal Response of Seismically Isolated Buildings with Friction Bearings
Publication: Journal of Structural Engineering
Volume 142, Issue 1
Abstract
This paper focuses on a horizontal-vertical coupling effect observed in a full-scale shake table experiment of a 5-story moment frame building isolated with triple pendulum bearings. A significant increase or amplification of the horizontal floor accelerations was observed during three-dimensional (3D) shaking compared to (horizontal only) shaking with comparable input motions. The coupling phenomenon is explained by analytical and numerical simulation of a single degree-of-freedom (rigid mass) structure and multistory cantilever structure subjected to simplified sinusoidal motions, both isolated with triple pendulum bearings. The results of the simplified numerical study are extended to explain the horizontal-vertical coupling in the full-scale experiment, which are also validated by numerical modeling of the test structure. The vertical component of ground acceleration is shown to introduce a high-frequency component into the base shear that can excite higher modes of the base-isolated structure. The phenomenon is possible in any multistory structure isolated with friction bearings, and should be evaluated on a case-by-case basis.
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Acknowledgments
The National Science Foundation through Grant No. CMMI-1113275 provided the funding for this study. NIED and Takenaka Corporation provided additional support for tests of a TP bearing isolation system at E-Defense. EPS donated the isolators, connection plates, and design services. The authors are grateful to all sponsors and participants for making these tests possible. The views reflected in this paper are those of the authors alone and do not necessarily reflect those of the sponsors or other project participants. The authors also recognize Anthony Giammona and Troy A. Morgan for their constructive review of the manuscript prior to submission.
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Information & Authors
Information
Published In
Journal of Structural Engineering
Volume 142 • Issue 1 • January 2016
Copyright
© 2015 American Society of Civil Engineers.
History
Received: Aug 31, 2014
Accepted: May 8, 2015
Published online: Jun 22, 2015
Discussion open until: Nov 22, 2015
Published in print: Jan 1, 2016
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