عنوان مقاله [English]
Steel reinforcing bars have not performed well in applications where members have been subjected to corrosive environments. To reduce the risk of reinforcement corrosion, several techniques have been employed. However, none of these methods have proven to serve as long-term solutions. Fiber-Reinforced Polymer (FRP) bars can be used as a reinforcing material by nature corrosion resistant. FRP reinforcing bars are available in different grades of tensile strength and modulus of elasticity. The behavior of concrete beams reinforced with FRP bars is different from that of steel reinforced concrete beams. FRP bars have high tensile strength and appropriate durability but are not ductile.
In addition, the bond between concrete and FRP bars is different from steel bars because of the difference in their surface geometries and mechanical characteristics.
In this experimental study, fifteen Lap-spliced concrete beams reinforced with
GFRP bars were manufactured and tested. The parameters of concrete compressive
strength, amount of transverse reinforcement along the splice length, the
surface conditions and the diameter of longitudinal bars were selected as the
variables for the beam specimens. There are ten specimens reinforced with
ribbed GFRP bars and five specimens reinforced with sand coated GFRP bars.
Laboratory specimens were designed so that bond failure occurs. The cracks of
the specimens were mapped and test observation was recorded during loading
steps and at the time of failure. Also, the relationships of force versus
mid-span displacement were obtained by means of a Load Cell, a LVDT (Linear
Variable Displacement Transducer), a Data Logger and a computer system. Then
the bond strength and ductility of specimens were analyzed. Based on the
experimental results, the effects of transverse reinforcement along the splice
length, concrete compressive strength and bar diameter on bond strength are
evaluated. The experimental results show that the effect of transverse
reinforcement along the splice length on bond strength of GFRP bars is largely
dependent on the surface conditions of the bars. Bond strength increases with
increase in the amount of transverse reinforcement. The concrete beams
reinforced with sand coated GFRP bars are more ductile than ribbed GFRP
reinforced concrete beams.looseness=-1
The results of forty three beam specimens tested by other researchers are used
in the study. The experimental bond strengths are compared with the values
obtained using CAN/CSA-S806-02 and ACI 440.1R-06 Code provisions. The
comparison shows that the bond strengths calculated with the code provisions
are higher than the experimental values especially in the specimens with no
transverse reinforcement along the splice length. Therefore, the code
provisions should be modified to consider the effect of transverse
reinforcement on bond strength.