The present experimental study addresses the structural response of reinforced concrete (RC) beam... more The present experimental study addresses the structural response of reinforced concrete (RC) beams strengthened in shear. Thirteen RC beams were divided into four different sets to investigate the effect of transverse and longitudinal steel reinforcement ratios, concrete compressive strength change and orientation for installing carbon fiber-reinforced polymer (CFRP) laminates. Then, we employed a shear strengthening solution through externally bonded reinforcement in grooves (EBRIG) and externally bonded reinforcement (EBR) techniques. In this regard, rectangular beams of 200x300x2000 mm dimensions were subjected to the 4-point static loading condition and their load-displacement curves, load-carrying capacity and ductility changes were compared. The results revealed that using EBRIG method, the gain percentage augmented with the increase in the longitudinal reinforcement ratio. Also, in the RC beams with stirrups, the gain in shear strength decreased as transverse reinforcement ratio increased. The results also revealed that the shear resistance obtained by the experimental tests were in acceptable agreement with the design equations. Besides, the results of this research indicated that using the EBRIG system through vertical grooves in RC beams with and without stirrups caused the energy absorption to increase about 85% and 97%, respectively, relative to the control.
This study aims to examine the behavior of reinforced concrete (RC) circular columns retrofitted ... more This study aims to examine the behavior of reinforced concrete (RC) circular columns retrofitted with ultra‐high‐performance fiber‐reinforced concrete (UHPFRC) jackets and fiber‐reinforced polymer (FRP) wraps under concentric and eccentric loading. In the present study, for the first time, UHPFRC jackets containing synthetic macro fibers (barchip) were used. The results were then compared with those obtained by UHPFRC containing steel fibers. Moreover, to improve the effect of concrete jacketing on the column behavior under eccentric loading, the innovative interface treatment of the longitudinal grooving method (GM) was applied. For these purposes, 15 such circular columns, 120 mm in diameter and 500 mm in height, were subjected to load eccentricities of 0, 30, and 60 mm. Thus, six columns were retrofitted with UHPFRC jackets 15 mm in thickness that included both steel and synthetic macro fibers (barchip) while another six were strengthened with UHPFRC jackets and intermittent glas...
This paper is focused on the results of the experimental investigation and numerical analysis for... more This paper is focused on the results of the experimental investigation and numerical analysis for changing the precast RC beam-column connections with corbels to flexural connections using fiber reinforced polymers (FRPs). The experimental study has a special focus on the flexural strength and debonding effect of boundary layer of FRP sheets attached onto the corbels and other parts of precast connections. In the current study, four half-scale external beam-to-column connections including one conventional fixed connection, and three simple precast connections with corbels strengthened with FRP sheets were casted and tested. The FRP sheets were attached in different layouts with different thicknesses. Static concentrated loads were applied on the tip of the beam simultaneously with a constant axial load on the column, and were continued up to ultimate failure. To fulfill the numerical phase of this study, non-linear static analysis on the 3-D model of the connections were performed u...
Helical auxetic yarn (HAY) is a newly developed composite yarn with negative Poisson’s ratio. HAY... more Helical auxetic yarn (HAY) is a newly developed composite yarn with negative Poisson’s ratio. HAYs offers advantageous merits as a reinforcing element in composite materials. In this paper high stiffness HAYs composed of Nylon filament core and fine steel wire wrap yarns were developed. The importance of the stiffness ratio of the wrap to the core components in the resultant auxetic yarn was examined. The differences between instantaneous and engineering Poisson’s ratio analyses in the understanding of the strain-dependent behavior of HAY was investigated. Results revealed that the utilization of the fine steel multifilament in the developed HAY samples enormously improves the stiffness of HAY. It was possible to obtain an elastic modulus of 9 GPa and a maximum auxetic effect of –16.82 in the samples. It was concluded that such highly stiff auxetic yarn can successfully be used as reinforcement in various composite materials such as cementitious composites.
The present experimental study addresses the structural response of reinforced concrete (RC) beam... more The present experimental study addresses the structural response of reinforced concrete (RC) beams strengthened in shear. Thirteen RC beams were divided into four different sets to investigate the effect of transverse and longitudinal steel reinforcement ratios, concrete compressive strength change and orientation for installing carbon fiber-reinforced polymer (CFRP) laminates. Then, we employed a shear strengthening solution through externally bonded reinforcement in grooves (EBRIG) and externally bonded reinforcement (EBR) techniques. In this regard, rectangular beams of 200x300x2000 mm dimensions were subjected to the 4-point static loading condition and their load-displacement curves, load-carrying capacity and ductility changes were compared. The results revealed that using EBRIG method, the gain percentage augmented with the increase in the longitudinal reinforcement ratio. Also, in the RC beams with stirrups, the gain in shear strength decreased as transverse reinforcement ratio increased. The results also revealed that the shear resistance obtained by the experimental tests were in acceptable agreement with the design equations. Besides, the results of this research indicated that using the EBRIG system through vertical grooves in RC beams with and without stirrups caused the energy absorption to increase about 85% and 97%, respectively, relative to the control.
This study aims to examine the behavior of reinforced concrete (RC) circular columns retrofitted ... more This study aims to examine the behavior of reinforced concrete (RC) circular columns retrofitted with ultra‐high‐performance fiber‐reinforced concrete (UHPFRC) jackets and fiber‐reinforced polymer (FRP) wraps under concentric and eccentric loading. In the present study, for the first time, UHPFRC jackets containing synthetic macro fibers (barchip) were used. The results were then compared with those obtained by UHPFRC containing steel fibers. Moreover, to improve the effect of concrete jacketing on the column behavior under eccentric loading, the innovative interface treatment of the longitudinal grooving method (GM) was applied. For these purposes, 15 such circular columns, 120 mm in diameter and 500 mm in height, were subjected to load eccentricities of 0, 30, and 60 mm. Thus, six columns were retrofitted with UHPFRC jackets 15 mm in thickness that included both steel and synthetic macro fibers (barchip) while another six were strengthened with UHPFRC jackets and intermittent glas...
This paper is focused on the results of the experimental investigation and numerical analysis for... more This paper is focused on the results of the experimental investigation and numerical analysis for changing the precast RC beam-column connections with corbels to flexural connections using fiber reinforced polymers (FRPs). The experimental study has a special focus on the flexural strength and debonding effect of boundary layer of FRP sheets attached onto the corbels and other parts of precast connections. In the current study, four half-scale external beam-to-column connections including one conventional fixed connection, and three simple precast connections with corbels strengthened with FRP sheets were casted and tested. The FRP sheets were attached in different layouts with different thicknesses. Static concentrated loads were applied on the tip of the beam simultaneously with a constant axial load on the column, and were continued up to ultimate failure. To fulfill the numerical phase of this study, non-linear static analysis on the 3-D model of the connections were performed u...
Helical auxetic yarn (HAY) is a newly developed composite yarn with negative Poisson’s ratio. HAY... more Helical auxetic yarn (HAY) is a newly developed composite yarn with negative Poisson’s ratio. HAYs offers advantageous merits as a reinforcing element in composite materials. In this paper high stiffness HAYs composed of Nylon filament core and fine steel wire wrap yarns were developed. The importance of the stiffness ratio of the wrap to the core components in the resultant auxetic yarn was examined. The differences between instantaneous and engineering Poisson’s ratio analyses in the understanding of the strain-dependent behavior of HAY was investigated. Results revealed that the utilization of the fine steel multifilament in the developed HAY samples enormously improves the stiffness of HAY. It was possible to obtain an elastic modulus of 9 GPa and a maximum auxetic effect of –16.82 in the samples. It was concluded that such highly stiff auxetic yarn can successfully be used as reinforcement in various composite materials such as cementitious composites.
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