Behaviour of fibre-reinforced polymer (FRP) stirrups as shear reinforcement for concrete structures

Abstract

The corrosion of steel reinforcement in reinforced concrete structures has lead to widespread deterioration of many buildings and bridges that are now in need of costly repairs. Due to their location as the outermost layer of reinforcement within a concrete structure, steel stirrups are the first to corrode. Fibre reinforced polymers (FRP) provide an alternative that does not corrode and has many other benefits such as a high strength-to-weight ratio. However, the inherent disadvantages of FRP in certain loading situations are apparent with FRP stirrups and must be accounted for in design. Loading transversely to the fibres can cause significant losses in stirrup capacity. By bending the FRP to form an end anchorage for the stirrup within the concrete, the bent portion of the bar is subjected to stresses perpendicular to the direction of the fibres and will experience strength losses. Due to the diagonal nature of shear cracks, the vertical stirrups are subjected to stresses perpendicular to the fibre direction as the crack widens. This again leads to potential strength losses. This thesis presents the experimental program and results of 113 panel specimen tests completed to determine the losses of stirrup capacity as related to the bend effect and the inclined crack effect, determined through multiple variables. These results are analyzed to examine the effect of each variable on the strength of the stirrups. Based on these results, recommendations are made and design guidelines are presented for the use of FRP as shear reinforcement.