د سلام 1

Skip to PDF contentFlexural strengthening of reinSkip to PDF contentforced concrete beams with NSM-CFRP bars
using mechanical interlocking
Salam Al-Obaidi a,b, Yasir M. Saeed c,*, Franz N. Rad d
a Roads and Transportations Engineering Department, University of Al-Qadisiyah, Diwaniyah, 58001, Iraq
b Department of Civil and Environmental Engineering, Politecnico di Milano, Milan, Italy
c Department of Civil and Environmental Engineering, Portland State University, P. O. Box 751, Portland, OR, 97207, USA
d Department of Civil and Environmental Engineering at Portland State University, Portland, OR, 97201, USA
A R T I C L E I N F O
Keywords:
Concrete beams
Near surface mounted
NSM-CFRP
Strengthening
A B S T R A C T
Flexural strengthening of reinforced concrete (RC) beams using near-surface-mounted (NSM) technique has
become an attractive alternative for rehabilitation using fiber reinforced polymer (FRP) materials. Previous
studies have recommended using available anchoring techniques to overcome premature bonding failure. In this
study, mechanical interlocking grooves were utilized to delay or prevent debonding failure. The first part of the
study aimed to investigate the bond characteristics for NSM-CFRP bars by conducting several pullout tests on No.
6, No.10, and No.13 CFRP bars. Results indicate that mechanical interlocking grooves can significantly enhance
the bonding capacity and prevent or delay premature bonding failure. In the second part, the proposed NSM
CFRP strengthening technique was used to strengthen nine RC beams. In addition to longitudinal grooves, the
proposed technique consisted of 6 mm wide lateral grooves (or mechanical interlocking) placed at 76 mm on
center along the entire length of the strengthened beams. Steel reinforcement ratios of 0.7% and 0.4% were
selected. All beam specimens were tested under four-point bending until failure. Results showed that strengthening
was more effective for specimens with a lower steel reinforcement ratio. Percentages of enhancement in
flexural strength were between 34-68% and 60–128% for specimens with 0.7% and 0.4% steel reinforcement
ratios, respectively. Finally, a simple empirical model was created for the experimental results. Theoretical results
showed reasonable agreement with the experimental results. However, the maximum load carrying capacity
and flexural stiffness were overestimated for beams with a total reinforcement ratio (steel plus CFRP) larger than