Abstract
The effectiveness of externally bonded sprayed glass fiber reinforced polymer (Sprayed GFRP) in shear strengthening of RC beams under quasi-static loading is investigated. Different techniques were utilized to enhance the bond between concrete and Sprayed GFRP, involving the use of through bolts and nuts paired with concrete surface preparation through sandblasting and through the use of a pneumatic chisel prior to Sprayed GFRP application. It was found that roughening the concrete surface using a pneumatic chisel and using through bolts and nuts were the most effective techniques. Also, Sprayed GFRP applied on 3 sides (U-shaped) was found to be more effective than 2-sided Sprayed GFRP in shear strengthening. Sprayed GFRP increased the shear load-carrying capacity and energy absorption capacities of RC beams. It was found that the load-carrying capacity of strengthened RC beams was related to an effective strain of applied Sprayed GFRP. This strain was related to Sprayed GFRP configuration and the technique used to enhance the concrete-FRP bond. Finally, an equation was proposed to calculate the contribution of Sprayed GFRP in the shear strength of an RC beam.
Highlights
Many concrete structures such as bridges that are in use today have exceeded their design life
The following notations are used for beam designations: C: control, NS: no stirrups, S: stirrups (Φ4.75 at 160 mm), SS: stirrups (3Φ4.75 at 50 mm), B2: sprayed glass fiber reinforced polymer (GFRP) on 2 lateral sides of the beam, B3: sprayed GFRP on 3 sides of the beam, SB: sandblasted, EP: epoxy was used before spraying the GFRP, 4B: 4 through bolts, 6B: 6 through bolts, 6H: 6 through holes
(2) CSA S-806-02 [4] restricts the summation of shear resistance provided by steel stirrups (Vs) and FRP composite (Vfrp) to a certain value (Clause 11.3.2.2 Equation (11.2)) as follows: Vs + Vfrp ≤ 0.6λφc fc bwd, (2)
Summary
Many concrete structures such as bridges that are in use today have exceeded their design life. Code requirements have been changed, the shear requirements have become more stringent for concrete girders and especially for bridges, and allowable traffic loads have been increased. Some elements of these structures have been weakened due to corrosion of steel rebars containing longitudinal (tension and compression) and vertical (shear) reinforcements. This technique and relevant materials properties (glass fiber and polymer) have been discussed in detail elsewhere [2] This technique, as compared to externally bonded FRP fabrics and laminates, is quite new for strengthening of RC structures. Different thicknesses and schemes were used, and their effectiveness was evaluated under quasi-static loading
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