Abstract
Basalt fiber reinforced polymer (BFRP) composites are increasingly being used to retrofit concrete structures by external bonding. For such strengthened members, the BFRP-concrete interface plays the crucial role of transferring stresses. This study aims to investigate the fatigue behaviour of the interface under bending load. A series of tests were conducted on BFRP-concrete bonded joint, including static, fatigue, and postfatigue loading. The fatigue failure modes, the development of deflection, the evolution of BFRP strains, and the propagation of interfacial cracks were analysed. In addition, the debonding-induced fatigue life of BFRP-concrete bonded joints was studied. Finally, a new model of fatigue life was proposed by defining the effective fatigue bond stress. The results showed that the fatigue experience has a significant effect on the BFRP strength especially near the root of concrete transverse crack and on the bond performance of the adhesive near the interface crack tip. There are two main fatigue failure modes: BFRP rupture and BFRP debonding. The fatigue damage development of the bond interface has three stages: rapid, stable, and unstable growth. The proposed model for the debonding-induced fatigue life is more conservative for the BFRP-concrete bonded joints under pure shear load than for those under bending load.
Highlights
The strengthening technique of applying fiber reinforced polymer (FRP) composites in civil structures has many advantages, such as high-strength/weight ratio, good corrosion resistant, ease of handling and application, and the elimination of the need for heavy equipment [1, 2]
The failure process included three phases: an inclined crack of approximate 45∘ appeared from the bottom near the midspan in concrete; with the increase of loading, interface crack between basalt fiber reinforced polymer (BFRP) and concrete initiated at the root of the diagonal crack; the interfacial crack propagated under complete debonding of the BFRP
The debonding-induced fatigue life of FRP-concrete bonded joints has been analysed based on the present experimental results and the reported tests under pure shear loading
Summary
The strengthening technique of applying fiber reinforced polymer (FRP) composites in civil structures has many advantages, such as high-strength/weight ratio, good corrosion resistant, ease of handling and application, and the elimination of the need for heavy equipment [1, 2]. For strengthening with externally bonded FRP, the FRPconcrete bond interface is the crucial element of transferring stresses, and vulnerable for debonding which could result in the failure of the whole structure. This has led to numerous studies on the mechanical properties of FRP-concrete bond interface. The majority of these studies are focused on the interface under monotonic loading, with a limited number under dynamic loading [8]; very limited information is available for the fatigue performance of the FRP-concrete bond interface which is of dominate importance in cases such as highway and railroad bridges [9].
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