Seismic retrofitting of reinforced concrete frame structures using GFRP-tube-confined-concrete composite braces |
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Authors: | Nasim S Moghaddasi B Yunfeng Zhang Xiaobin Hu |
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Institution: | 1. Department of Civil and Environmental Engineering, University of Maryland, College Park, MD, 20742, USA 2. School of Civil and Architecture Engineering, Wuhan University, Wuhan, 430072, China
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Abstract: | This paper presents a new type of structural bracing intended for seismic retrofitting use in framed structures. This special
composite brace, termed glass-fiber-reinforced-polymer (GFRP)-tube-confined-concrete composite brace, is comprised of concrete
confined by a GFRP tube and an inner steel core for energy dissipation. Together with a contribution from the GFRP-tube confined
concrete, the composite brace shows a substantially increased stiffness to control story drift, which is often a preferred
feature in seismic retrofitting. An analysis model is established and implemented in a general finite element analysis program
— OpenSees, for simulating the load-displacement behavior of the composite brace. Using this model, a parametric study of
the hysteretic behavior (energy dissipation, stiffness, ductility and strength) of the composite brace was conducted under
static cyclic loading and it was found that the area ratio of steel core to concrete has the greatest influence among all
the parameters considered. To demonstrate the application of the composite brace in seismic retrofitting, a three-story nonductile
reinforced concrete (RC) frame structure was retrofitted with the composite braces. Pushover analysis and nonlinear time-history
analyses of the retrofitted RC frame structure was performed by employing a suite of 20 strong ground motion earthquake records.
The analysis results show that the composite braces can effectively reduce the peak seismic responses of the RC frame structure
without significantly increasing the base shear demand. |
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Keywords: | brace composite confined concrete glass-fiber-reinforced polymer frame nonlinear analysis retrofit seismic |
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