Effects of Aftershocks on the Potential Damage of FRP-Retrofitted Reinforced Concrete Structures
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RESEARCH PAPER
Effects of Aftershocks on the Potential Damage of FRP-Retrofitted Reinforced Concrete Structures Vui Van Cao1,2 Received: 5 August 2019 / Revised: 13 May 2020 / Accepted: 5 June 2020 Iran University of Science and Technology 2020
Abstract This study investigates the effects of aftershocks on the potential damage of reinforced concrete (RC) structures retrofitted by fibre-reinforced polymer (FRP). An eight-storey RC frame that was poorly confined due to deficient transverse reinforcement was selected and then retrofitted by FRP wraps to provide external confinement. Inelastic time history and damage analyses of the frame under single earthquakes and mainshock–aftershock sequences were performed. FRP retrofit did not ensure a damage-free structure, and it minimised the damage though. The results indicated different contributions of aftershocks to the damage of the retrofitted frame, and this finding illustrates the limitations of current seismic codes. The damage caused by single earthquakes is proposed to be used as a criterion for dealing with the effects of aftershocks as follows. If the mainshocks cause minor or light damage, the effect of aftershocks is negligible, whereas the effect of aftershocks needs to be considered if the mainshocks cause moderate or severe damage. The outcomes of this study can be used in making decisions about whether the effects of aftershocks should be considered. Keywords FRP Confinement Damage RC structure Mainshock Aftershock
1 Introduction Transverse reinforcement provides the confinement effect that increases the strength and ductility of concrete and consequently increases the seismic capacity of structures. The design of transverse reinforcement for reinforced concrete (RC) structures has been changed considerably since the concept of ductile structures was implemented, and many existing building structures all over the world are deficient because they were designed and built during 1970s and 1980s. For these buildings, gravity loads were the major design loads, while earthquake loading was ignored or it was considered with a lower intensity than in
& Vui Van Cao [email protected]; [email protected] 1
Department of Mechanics of Materials and Structures, Faculty of Civil Engineering, Ho Chi Minh City University of Technology (HCMUT) – Vietnam National University, 268 Ly Thuong Kiet Street, District 10, Ho Chi Minh City, Vietnam
2
Vietnam National University Ho Chi Minh City, Linh Trung Ward, Thu Duc District, Ho Chi Minh City, Vietnam
current seismic codes, and transverse reinforcement is commonly found to be deficient. Subsequently, many existing RC building structures are vulnerable to earthquake ground motions, as evident from the damage caused in past global seismic events such as those of Northridge in 1994, Kobe in 1995, Chi–Chi in 1999, Bam in 2003 and Christchurch in 2011. Deficient building structures in seismic regions can either be strengthened or demolished and rebuilt. Considerable r
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