Various FRP-Bracing Configurations for Multistory Buildings under Seismic Loading: Conceptual Modeling and Comparative Assessment
Publication: Journal of Composites for Construction
Volume 21, Issue 3
Abstract
This paper presents the behavior of multistory buildings with fiber-reinforced polymer (FRP) brace members for new construction and for retrofit applications, including a comparative assessment against conventional steel brace systems. The El Centro earthquake load with a magnitude of 7.1 is employed to examine the performance of three brace types (hollow structural steel sections, and pultruded carbon FRP (CFRP) and glass FRP (GFRP) tubes for new buildings; and CFRP-confined and aramid FRP (AFRP)-confined concrete elements for existing buildings: seismic strengthening with FRP wrapping) and three shapes frequently used in practice (single-bay X-brace, super X-brace, and chevron brace). Nonlinear pushover and time-history models are developed to predict the seismic response of the retrofitted buildings with an emphasis on base shear force, ductility, mode shapes and frequencies, and strain energy. The brace materials and confinement schemes of the buildings control the effectiveness of the seismic-retrofit rather than the brace shapes. The FRP-braced buildings show strain energy characteristics comparable with those of the steel-braced buildings, although the ductility index of the latter is higher than the index of the former. The FRP-based braces reduce the maximum kinetic energy of the buildings up to 64% in comparison with the steel braces. However, the -delta effect is a concern when pultruded FRP tubes are used because of their low elastic modulus. The FRP-confined concrete braces are effective in terms of lowering the dynamic amplification of the buildings relative to their steel and pultruded FRP counterparts.
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Acknowledgments
The authors gratefully acknowledge financial support from the University of Colorado, Denver, and are indebted to anonymous reviewers for their insightful comments and practical suggestions. Proprietary information such as FRP product names was excluded in the paper to avoid commercialism.
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Published In
Journal of Composites for Construction
Volume 21 • Issue 3 • June 2017
Copyright
©2016 American Society of Civil Engineers.
History
Received: Apr 23, 2016
Accepted: Aug 23, 2016
Published online: Oct 18, 2016
Discussion open until: Mar 18, 2017
Published in print: Jun 1, 2017
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