Bond Behaviour of Near-Surface Mounted Strips in RC Beams-Experimental Investigation and Numerical Simulations.

Renata Kotynia,Hussien Abdel Baky,Kenneth W Neale

doi:10.3390/ma14164362

Renata Kotynia, Hussien Abdel Baky + Show 1 more

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https://doi.org/10.3390/ma14164362

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Journal: Materials	Publication Date: Aug 4, 2021
Citations: 5	License type: CC BY 4.0

Affiliation: Lodz University of Technology

Abstract

This paper presents an investigation of the bond mechanism between carbon fibre reinforced polymer (CFRP) laminates, concrete and steel in the near-surface mounted (NSM) CFRP-strengthened reinforced concrete (RC) beam-bond tests. The experimental program consisting of thirty modified concrete beams flexurally strengthened with NSM CFRP strips was published in. The effects of five parameters and their interactions on the ultimate load carrying capacities and the associated bond mechanisms of the beams are investigated in this paper with consideration of the following investigated parameters: beam span, beam depth, longitudinal tensile steel reinforcement ratio, the bond length of the CFRP strips and compressive concrete strength. The longitudinal steel reinforcement was cut at the beam mid-span in four beams to investigate a better assessment of the influence of the steel reinforcement ratio on the bond behaviour of CFRP to concrete bond behaviour. The numerical analysis implemented in this paper is based on a nonlinear micromechanical finite element model (FEM) that was used for investigation of the flexural behaviour of NSM CFRP-strengthened members. The 3D model based on advanced CFRP to concrete bond responses was introduced to modelling of tested specimens. The FEM procedure presents the orthotropic behaviour of the CFRP strips and the bond response between the CFRP and concrete. Comparison of the experimental and numerical results revealed an excellent agreement that confirms the suitability of the proposed FE model.

Highlights

In the last two decades, an enormous amount of research work and numerous innovative applications have been published in the field of externally bonded (EB) fibre-reinforced polymer (FRP) concrete structures
Failure modes of the tested near-surface mounted (NSM) carbon fibre reinforced polymer (CFRP) strengthened beams occurred by the strip debonding together with the surrounding concrete cover along or slightly above the level of the steel reinforcement [48]
The beams with the cut steel reinforcement failure mode were different from those with longitudinal reinforcement, characterized by the CFRP debonding from the surrounding concrete cover, above the level of the internal steel reinforcement (Figure 4e)

Summary

Introduction

In the last two decades, an enormous amount of research work and numerous innovative applications have been published in the field of externally bonded (EB) fibre-reinforced polymer (FRP) concrete structures. The near-surface mounted technology has become very effective for flexural strengthening in single-span and double-span members, especially in the negative moment regions, where externally bonded FRP reinforcement is sensitive to environmental and mechanical impacts. The interactions between the internal reinforcement and the externally bonded NSM strips on the stress transfer between the CFRP laminates and surrounding concrete have been published in [20,21,22,23,24,25,26,27,28]

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