Strengthening of RC Beams Using Externally Bonded Reinforcement Combined with Near-Surface Mounted Technique.

Kh Darain,Nusrat Hoque,Md Hosen,M Obaydullah,Md Huda,Ahmad Shukri,Mohd Jumaat

doi:10.3390/polym8070261

Kh Darain, Nusrat Hoque + Show 5 more

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https://doi.org/10.3390/polym8070261

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Journal: Polymers	Publication Date: Jul 19, 2016
Citations: 36	License type: CC BY 4.0

Affiliation: University of Malaya, Khulna University

Abstract

This study investigates the flexural behaviour of reinforced concrete (RC) beams strengthened through the combined externally bonded and near-surface mounted (CEBNSM) technique. The externally bonded reinforcement (EBR) and near-surface mounted (NSM) techniques are popular strengthening solutions, although these methods often demonstrate premature debonding failure. The proposed CEBNSM technique increases the bond area of the concrete–carbon fibre reinforced polymer (CFRP) interface, which can delay the debonding failure. This technique is appropriate when any structure has a narrow cross-sectional width or is in need of additional flexural capacity that an individual technique or material cannot attain. An experimental test matrix was designed with one control and five strengthened RC beams to verify the performance of the proposed technique. The strengthening materials were CFRP bar as NSM reinforcement combined with CFRP fabric as EBR material. The test variables were the diameter of the NSM bars (8 and 10 mm), the thickness of the CFRP fabrics (one and two layers) and the U-wrap anchorage. The strengthened beams showed enhancement of ultimate load capacity, stiffness, cracking behaviour, and strain compatibility. The ultimate capacity of the CEBNSM-strengthened beams increased from 71% to 105% compared to that of the control beam. A simulation method based on the moment-rotation approach was also presented to predict the behaviour of CEBNSM-strengthened RC beams.

Highlights

Throughout the world, the growing interest in the sustainability of construction encourages the engineering community to develop policies that discourage new construction rather than extend the design life of existing structures [1]
This study proposes the development of another type of combined externally bonded and near-surface mounted (CEBNSM) strengthening technique involving the use of EB fibre-reinforced polymer (FRP) sheets with near-surface mounted (NSM) FRP bars or NSM steel bars, with the aim of developing a cost-effective strengthening solution which will delay or avoid the debonding failure seen in the previous study
These beams were strengthened with the carbon fibre reinforced polymer (CFRP) bar inside the NSM groove and the CFRP fabric bonded at the beam soffit

Summary

Introduction

Throughout the world, the growing interest in the sustainability of construction encourages the engineering community to develop policies that discourage new construction rather than extend the design life of existing structures [1]. Fibre-reinforced polymer (FRP) has substituted conventional strengthening materials such as steel and concrete because of its high strength-to-weight ratio, resistance to corrosion, and low density [5,6,7,8,9,10]. The externally bonded reinforcement (EBR) and near-surface mounted (NSM) strengthening techniques are gaining popularity. The EBR technique consists of one or multiple FRP laminates that are bonded. The NSM technique involves the insertion of FRP strips or rods into pre-cut grooves in concrete covers and filling up with epoxy adhesives [12]. The NSM technique is a contemporary technique that offers a high level of strengthening efficacy, is less prone to premature debonding failure, and enhances protection against fire, mechanical damage, the effects of aging, and acts of vandalism. The technique demonstrates better durability, stress-sharing mechanisms, and fatigue performance, given that the reinforcement is located inside [13]

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