Civil and Architectural Engineering
Civil and Architectural Engineering
Department-College of Engineering-Sultan Qaboos University
Upgrading the Flexural Capacity of Reinforced Concrete Beams Using Glass
Fiber Reinforced Polymers
Sultan Mohammed Saif Al Mazroui
Abstract
This research study aims to investigate the flexural behavior of reinforced concrete beams
strengthened with different types of Glass Fiber Reinforced Polymers (GFRP) using different
strengthening techniques. The experimental work includes the construction and testing of eleven
(11) full scale reinforced concrete beams of 200mm × 300mm × 2760mm (width × depth ×
length). The research study includes four parameters: the strengthening technique used (Near
surface mounted (NSM) and externally bonded (EB)), type of GFRPs (Glass FRP bars and
Glass FRP sheets), amount of GFRPs, and additional anchorage system. All the eleven (11)
beam specimens included a reference beam (without strengthening). Six (6) beams strengthened
with near surface mounted (NSM) technique using two different types of GFRP bars. The
remaining four (4) beams were strengthened with externally bonded (EB) technique using
GFRP sheets with different anchorage systems. After strengthening, all the beams were tested in
flexure under four point bending set-up. The experimental test results include ultimate capacity,
deflection, cracking, reinforcement and concrete strains, and mode of failure have been
recorded.
All the strengthened beams showed an increase in the ultimate load capacity. The increase
ranged between 41 and 166% compared with the reference beam. Three NSM strengthened
beams (with type 1 GFRP bars) failed by steel yielding followed by rupture of the GFRP bars.
The other three NSM strengthened beams (with type 2 GFRP bars) failed by steel yielding
followed by concrete crushing followed by debonding of the GFRP bars and they showed good
ductile behavior with high deflection values at ultimate load which were almost similar or even
higher than that recorded in the reference beam. This gives an amble warning before failure and
can be considered as an important advantage of this technique. EB In-groove technique showed
the best results out of all used techniques in term of ultimate capacity. This approved that
externally bonded with in-groove technique system did show extra advantage compared with
EB and on-groove techniques. Both types of additional anchorage systems (intermediate
grooves for NSM and U-shape in EB) showed great advantages in both EB and NSM
strengthened beams in terms of increasing ultimate capacity and improving ductility behavior
by delaying the debonding of FRP. The load carrying capacities of the tested specimens were
also calculated using the ISIS Design Manual guidelines and compared to the experimental
results.