Abstract
The literature related to earthquakes and fibre reinforced polymer (FRP) retrofitting can be divided into two main categories: (1) the applications of FRP to retrofit structures subjected to single traditional earthquakes and (2) the effects of mainshock-aftershock sequences on original structures (without FRP retrofitting). Research on using FRP to mitigate the risk of pulse-type mainshock-aftershock sequences for reinforced concrete (RC) structures located in near-fault regions is hardly found in the literature and is thus the aim of this study. To achieve this aim, a four-storey RC frame, near-fault mainshocks, and seismic sequences were selected. The frame was retrofitted using FRP wraps at plastic hinge locations. Nonlinear time history and damage analyses of the original and FRP-retrofitted frames subjected to these near-fault mainshocks and seismic sequences were conducted. The results showed that aftershocks significantly increase the damage indices of the frames, shifting the damage state of the original frame from severe damage to collapse and the damage state of the FRP-retrofitted frame from light damage to moderate damage. FRP retrofitting successfully reduced the risk of seismic sequences by reducing the damage two levels, shifting the damage state of the original frame from collapse to moderate damage.
Highlights
Academic Editor: John Mander e literature related to earthquakes and fibre reinforced polymer (FRP) retrofitting can be divided into two main categories: (1) the applications of FRP to retrofit structures subjected to single traditional earthquakes and (2) the effects of mainshock-aftershock sequences on original structures
Yang et al [41] evaluated the damage demand of an eight-storey reinforced concrete (RC) frame subjected to near-fault seismic sequences and the results showed that the aftershocks decreased the collapse capacity of structures while the near-fault pulse-type aftershocks increased the storey damage demand
Amongst many types of FRP, GFRP has been the most technically and economically suitable FRP type for confinement of RC structures [19, 23, 79]. e tensile strength, elastic modulus, and thickness of unidirectional GFRP sheets, respectively, are 3241 MPa, 72397 MPa, and 0.589 mm [82]. e aim of this paper is to evaluate the damage potential reduction of FRP retrofitting on RC frames subjected to seismic sequences; two GFRP layers were applied to columns. e length of GFRP wrapped columns is assumed to be twice the plastic hinge length lp
Summary
Received 29 November 2019; Revised 31 May 2020; Accepted 10 June 2020; Published 8 July 2020. Hatzivassiliou and Hatzigeorgiou [40] studied the effects of seismic sequences on the inelastic responses of 3D RC frames and indicated that the aftershocks increased the displacement while the directions of earthquake ground motions significantly affected the structural ductility demand. The effectiveness of FRP retrofitting to reduce the seismic damage and collapse risk of building structures located in near-fault regions with and without aftershocks was investigated in this paper. To achieve this aim, a four-storey RC frame representing low-rise building structures was selected. Mainshock-Aftershock Sequences ree approaches have been implemented by researchers to obtain mainshock-aftershock sequences: (1) repeating the selected records [29, 32, 33, 66, 67], (2) randomizing [24, 29, 38, 66,67,68], and (3) using real seismic sequences [66]
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