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Joaquim A. O. Barros - One of the best experts on this subject based on the ideXlab platform.

  • Flexural Strengthening of masonry members using advanced cementitious materials
    2020
    Co-Authors: Joaquim A. O. Barros, Esmaeel Esmaeeli, Elizabeth Campbell Manning, D. Häßler
    Abstract:

    Two different cement based fiber reinforced composites for the Flexural Strengthening of masonry beams under monotonic loading are studied. Steel Fiber Reinforced SelfCompacting Concrete (SFRSCC) with tensile strain-softening behavior, and PVA fiber reinforced cement based mortar (SHCC) with tensile Strain-Hardening were the developed composites. Both composites were applied on the tensile surface of masonry beams and the effectiveness of this technique for the Flexural Strengthening of these quasi-brittle structural elements was assessed by performing four point beam bending tests. Both materials contributed effectively to increase the load carrying capacity and ultimate deflection ductility of the tested masonry beams, but, higher average values were obtained for these two indicators of the Strengthening effectiveness when using a layer thickness of SHCC that is 2/3 of the thickness of SFRSCC. Furthermore, much more homogenous results, in terms of forcedeflection relationship, were obtained with masonry beams strengthened with SHCC than with SFRSCC.

  • Efficiency of different FRP-based Flexural Strengthening techniques in beams submitted to fatigue loading
    2020
    Co-Authors: José Sena-cruz, Joaquim A. O. Barros, Mário Rui Freitas Coelho, Luís F. F. T. Silva
    Abstract:

    Flexural Strengthening of reinforced concrete (RC) structures with fiber reinforced polymers (FRP) has been used mostly by two main techniques: Externally Bonded Reinforcement (EBR) and Near-Surface Mounted (NSM). In both Strengthening techniques the FRP systems are applied on the cover concrete, which is normally the weakest region of the element to be strengthened. Consequently, the most common problem is the premature failure of the system, which occurs more frequently when using the EBR technique. In an attempt of overcoming this weakness, another Flexural Strengthening technique, named MF-EBR – Mechanically Fastened and Externally Bonded Reinforcement, is analyzed in the present paper. This technique uses multidirectional carbon fiber laminates that are simultaneously glued and anchored to concrete. To compare the efficiency of NSM, EBR and MF-EBR techniques, four-point bending tests with RC beams were carried out under monotonic and fatigue loading. In this work the tests are described and the obtained results are presented and discussed.

  • exploring new nsm reinforcements for the Flexural Strengthening of rc beams experimental and numerical research
    Composite Structures, 2016
    Co-Authors: Mohammadali Rezazadeh, Renata Kotynia, Szymon Cholostiakow, Joaquim A. O. Barros
    Abstract:

    Abstract Carbon-fiber-reinforced-polymer (CFRP) composite materials applied according to near-surface-mounted (NSM) technique constitute an effective technique for the Flexural and shear Strengthening of reinforced-concrete (RC) structures. However, the NSM CFRP reinforcement ratio is limited by the thickness of concrete cover of the longitudinal tensile steel bars, and the minimum distance between consecutive CFRPs, below which premature fracture of surrounding concrete occurs due to group effect. Hence, the current study aims to experimentally and numerically evaluate the Strengthening potentialities of a novel NSM system (with high CFRP ratio capability) for the Flexural Strengthening of RC beams. This new system combines externally-bonded-reinforcement (EBR) and NSM techniques in the same application using T-shaped CFRP profiles. The obtained experimental results of the RC beams strengthened with CFRP profiles are presented and discussed with the aim of evaluating the influence of CFRP profile reinforcement ratio on the Strengthening efficiency of this technique. A developed 3D finite-element (FE) approach is used to simulate the experimental tests. After demonstrating its good predictive performance, a series of parametric studies is performed to assess the influence of the main material properties, and ratio of bond area to cross sectional area of the CFRP profiles on the efficiency of the proposed system.

  • Flexural Strengthening of reinforced low strength concrete slabs using prestressed nsm cfrp laminates
    Composites Part B-engineering, 2016
    Co-Authors: Mhoammadreza Mostakhdemin Hosseini, Salvador J E Dias, Joaquim A. O. Barros
    Abstract:

    Abstract The effectiveness of the Near Surface Mounted (NSM) technique with prestressed CFRP (carbon fiber reinforced polymer) laminates for the Flexural Strengthening of reinforced concrete (RC) slabs of low strength concrete was assessed. Four RC slabs were tested, a reference slab (without CFRP), and three slabs Flexurally strengthened using NSM CFRP laminates with different prestress level of the ultimate tensile strength of the CFRP: 0%, 20% and 40%. The experimental program is described and the main results are presented and analyzed in terms of the structural behavior of the RC slabs, failure modes and performance of the NSM technique with prestressed CFRP laminates. The results show that prestressing CFRP laminates with NSM technique is an effective technology to increase cracking, service, yielding and maximum loads of RC slabs made by low strength concrete. By applying NSM CFRP laminates prestressed at 20%, the cracking, service and maximum loads have increased, respectively, 258%, 123% and 125%, when the corresponding values of the reference slab are taken for comparison purposes, while 400%, 190% and 134% were the increase when applying laminates prestressed at 40%. Using available experimental results obtained with the same test setup, but using RC slabs of higher strength concrete, it can be concluded that as minimum is the concrete strength as more effective is the NSM technique with prestressed CFRP laminates in terms of serviceability limit states. A numerical strategy was used to evaluate the load-deflection of the tested RC slabs and to highlight the influence of the percentage of CFRP, the percentage of tensile longitudinal bars and the elasticity modulus of the CFRP on the effectiveness of the NSM technique with prestressed CFRP laminates for the Flexural Strengthening of RC slabs, by performing a parametric study.

  • a new hybrid methodology according to near surface mounted carbon fiber reinforced polymer technique for the Flexural Strengthening of reinforced concrete beams
    Journal of Reinforced Plastics and Composites, 2014
    Co-Authors: Mohammadali Rezazadeh, Joaquim A. O. Barros
    Abstract:

    The objective of this paper is to propose a new hybrid methodology according to near surface mounted (NSM) technique, using carbon fiber reinforced polymer (CFRP) reinforcement for the Flexural Strengthening of reinforced concrete (RC) beams. This NSM hybrid Flexural Strengthening technique combines non-prestressed and prestressed CFRP laminates in the same application in order to provide a good balance in terms of load-carrying and ultimate displacement capacity to the strengthened elements. An experimental program composed of six RC beams was carried out to assess the benefits of this NSM hybrid technique when compared to the use of non-prestressed or prestressed NSM CFRP laminates (NSM prestressing technique). For this purpose, the performance of both techniques in terms of crack width, prevailing failure mode, ultimate displacement capacity, energy absorption, and load-carrying capacity of the strengthened beams was assessed. The experimental tests were also simulated by executing advanced 3D nonlinea...

Dionysios A Bournas - One of the best experts on this subject based on the ideXlab platform.

  • Flexural Strengthening OF RC COLUMNS WITH NSM FRP OR STAINLESS STEEL
    2020
    Co-Authors: Dionysios A Bournas
    Abstract:

    The paper presents the results of a large-scale experimental program aiming to study the behavior of reinforced concrete (RC) columns under simulated seismic loading, strengthened in flexure (of crucial importance in capacity design) with different types and configurations of near-surface mounted (NSM) reinforcing materials. The role of different parameters is examined, by comparison of the lateral load versus displacement response characteristics (peak force, drift ratios, energy dissipation, stiffness). Those parameters were as follows: carbon or glass fiber-reinforced polymers (FRP) versus stainless steel; configuration and amount of NSM reinforcement; confinement via local jacketing; and type of bonding agent (epoxy resin or mortar). The results demonstrate that NSM FRP and stainless steel reinforcement is a viable solution towards enhancing the Flexural resistance of reinforced concrete columns subjected to seismic loads. This is especially the case, when the retrofitting scheme combines epoxy-bonded NSM bars with local confining jackets (provided in this study with textile-reinforced mortars – TRM).

  • trm versus frp in Flexural Strengthening of rc beams behaviour at high temperatures
    Construction and Building Materials, 2017
    Co-Authors: Saad M Raoof, Dionysios A Bournas
    Abstract:

    The Flexural behaviour of RC beams strengthened with TRM and FRP composites was experimentally investigated and compared both at ambient and high temperatures. The investigated parameters were: (a) the Strengthening material, namely TRM versus FRP, (b) the number of Strengthening layers, (c) the textile surface condition (dry and coated), (d) the textile material (carbon, basalt or glass fibres) and (e) the end-anchorage of the Flexural reinforcement. A total of 23 half-scale beams were constructed, strengthened in flexure and tested to assess these parameters and the effectiveness of the TRM versus FRP at high temperatures. TRM exhibited excellent performance as Strengthening material in increasing the Flexural capacity at high temperature; in fact, TRM maintained an average effectiveness of 55%, compared to its effectiveness at ambient temperature, contrary to FRP which totally lost its effectiveness when subjected to high temperature. In specific, from the high temperature test it was found that by increasing the number of layers, the TRM effectiveness was considerably enhanced and the failure mode was altered; coating enhanced the TRM effectiveness; and the end-anchorage at high temperature improved significantly the FRP and marginally the TRM effectiveness. Finally, the formula proposed by the Fib Model Code 2010 was used to predict the mean debonding stress in the TRM reinforcement, and using the experimental results obtained in this study, a reduction factor to account for the effect of high temperature on the Flexural Strengthening with TRM was proposed.

Alessandra Aprile - One of the best experts on this subject based on the ideXlab platform.

  • a parametric study on the effectiveness of the nsm technique for the Flexural Strengthening of continuous rc slabs
    Composites Part B-engineering, 2012
    Co-Authors: Matteo Breveglieri, Joaquim A. O. Barros, Glaucia Dalfre, Alessandra Aprile
    Abstract:

    Abstract Recent experimental research has shown that the Near Surface Mounted (NSM) technique has significant potential for increasing the load-carrying capacity of continuous reinforced concrete (RC) slabs. This Flexural Strengthening technique is based on the installation of rectangular cross sectional carbon fibre reinforced polymer (CFRP) laminates into thin slits that have been opened into the top concrete cover on intermediate supports as well as into the bottom concrete cover in the tensile zones. However, there are several drawbacks to the NSM technique. The linear-elastic behaviour of the CFRP laminates, combined with the possibility of premature detachment of the concrete cover that includes these laminates, can compromise the effectiveness of the Flexural Strengthening, the moment redistribution and the ductility performance of this type of structure. In order to evaluate the influence of concrete strength, the Strengthening configuration, the percentage of CFRP on the load-carrying capacity, the moment redistribution ability and ductility performance of this type of structure, a parametric study was carried out by executing material nonlinear analysis with an FEM-based computer program, whose predictive performance was calibrated based on the results of a previous experimental program.

  • Assessment of the effectiveness of NSM-CFRP Flexural Strengthening configuration for continuous RC slabs
    2011
    Co-Authors: Matteo Breveglieri, Joaquim A. O. Barros, Glaucia Dalfre, Alessandra Aprile
    Abstract:

    The experimental programs for the Flexural Strengthening of reinforced concrete (RC) structures using the Near Surface Mounted (NSM) technique with Fiber Reinforced Polymer (FRP) laminates were, in general, conducted with simply supported beams. Therefore, there is a lack of experimental and theoretical studies on the moment redistribution of statically indeterminate RC elements strengthened with NSM technique. This work explores the influence of the amount of FRP in terms of load carrying capacity, ductility and moment redistribution capacity of continuous RC slab strips. In this way, two span slab strips strengthened in the hogging region were tested. The obtained results were used to assess the predictive performance of a finite element model in the simulation of the nonlinear behavior of the tested slabs. Finally, a parametric study is carried out to investigate the influence of the Strengthening arrangement and FRP percentage in terms of load carrying capacity and moment redistribution capacity of continuous RC slab strips Flexurally strengthened by the NSM technique.

Raafat Elhacha - One of the best experts on this subject based on the ideXlab platform.

  • anchorage system to prestress frp laminates for Flexural Strengthening of steel concrete composite girders
    Journal of Composites for Construction, 2013
    Co-Authors: Raafat Elhacha
    Abstract:

    Using externally bonded (EB) fiber-reinforced polymer (FRP) laminates for Strengthening steel-concrete composite girders has recently received more attention from researchers. By prestressing the EB FRP laminates, the material is used more efficiently because a greater portion of its tensile capacity is employed and it contributes to the load-bearing capacity under both service and ultimate conditions. This is an ideal technique because it combines the advantage of using noncorrosive and lightweight advanced composite materials in the form of bonded FRP laminates with the high efficiency offered by external prestressing. An innovative mechanical anchorage system was developed to prestress the FRP laminates directly by jacking and reacting against the steel girder itself. The efficiency of the system was investigated using two types of FRP laminates for Flexural Strengthening of large-scale steel-concrete composite girders. The used FRP composite materials included carbon-fiber-reinforced polymer (CFRP) plate and steel-fiber-reinforced polymer (SFRP) sheets. The developed anchorage/prestressing system was easy to use/apply and proved to be a feasible and practical system for prestressing both CFRP plate and SFRP sheet. The prestressing levels in the FRP laminates were sufficiently maintained. The prestressing losses were insignificant.

  • Flexural Strengthening of rc beams using steel reinforced polymer srp composites
    Special Publication, 2005
    Co-Authors: A Kong, Raafat Elhacha
    Abstract:

    Synopsis: This paper presents the application of a new generation of externally bonded composite material in Flexural Strengthening of reinforced concrete beams. The steel reinforced polymer (SRP) composite consists of high-carbon steel unidirectional Hardwire® fabrics embedded in epoxy resin, and offers high strength and stiffness characteristics at a reasonable cost. In this paper, the mechanical properties of SRP are evaluated and its application in Flexural Strengthening of RC beams is investigated. Six beams have been tested in three-point bending to study the effect of SRP retrofitting on Flexural behavior, failure modes, and crack patterns. Test parameters include variation of the width of SRP sheets and the use of SRP U-wraps at both ends to prevent premature failure caused by delamination of the longitudinal sheet. Significant increase in Flexural capacity, up to 53 %, and pseudo-ductile failure modes have been observed in the SRP-strengthened beams. Failure is governed primarily by concrete cover delamination at the tips of the SRP sheets or crushing of concrete at mid-span. It is also shown that the U-wraps have improved Flexural stiffness by means of controlling diagonal crack width and providing anchorages to the longitudinal SRP sheets, which reduces their slip. Shear stress concentration near the cut-off point of the SRP sheet has also been investigated. An analytical model is proposed to predict the nominal strength of the SRP-strengthened beams.

Faouzi Ghrib - One of the best experts on this subject based on the ideXlab platform.

  • effect of the fiber type and axial stiffness of frcm on the Flexural Strengthening of rc beams
    Fibers, 2017
    Co-Authors: Abdulla Jabr, Amr Elragaby, Faouzi Ghrib
    Abstract:

    The use of externally-bonded fiber-reinforced polymer (FRP) sheets has been successfully used in the repair and Strengthening of both the shear and Flexural capacities of reinforced concrete (RC) beams, slabs and columns since the 1990s. However, the externally-bonded FRP reinforcements still present many disadvantages, such as poor performance in elevated temperature and fire, lack of permeability and strength degradation when exposed to ultraviolet radiation. To remedy such drawbacks, the fiber-/fabric-reinforced cementitious matrix (FRCM) has been recently introduced. The FRCM system consists of a fiber mesh or grid embedded in a cementitious bonding material. The present research investigates the Flexural Strengthening of reinforced concrete (RC) beams with FRCM. The experimental testing included eight large-scale concrete beams, 150 mm × 250 mm × 2400 mm, internally reinforced with steel bars and strengthened in flexure with FRCM. The investigated parameters were the internal steel reinforcement ratio and the FRCM systems. Two steel reinforcement ratios of 0.18 and 0.36 of the balanced reinforcement ratio, as well as three FRCM systems using glass, carbon and PBO fibers were investigated. Test results are presented in terms of load-deflection, load-strain and load-crack width relationships. The test results indicated that the PBO FRCM significantly increased the ultimate capacity of the strengthened RC beams with both low and moderate internal reinforcement ratios compared to the glass and carbon FRCM.

  • Flexural Strengthening of reinforced concrete slab column connection using cfrp sheets
    Construction and Building Materials, 2014
    Co-Authors: Hazem A Elenein, Hossein Azimi, Khaled Sennah, Faouzi Ghrib
    Abstract:

    Abstract The objective of this paper is to investigate experimentally the effectiveness of application of carbon fiber reinforced polymer (CFRP) sheets as a Strengthening technique of a reinforced concrete (RC) slab–column connection in one-way flat-plate system to enhance its Flexural strength. The experimental study was particularly conducted to examine whether there is enough anchorage with the use of CFRP wrapping to the discontinuous longitudinal CFRP sheets at column stub. Series of tests were conducted on six flat slab–column connection specimens organized in two groups of three specimens each. The first group included three control specimens with central, eccentric, and edge columns, respectively. The second group was geometrically identical to the first group, though with CFRP sheets installed on the tension side of the slab to increase Flexural capacity at the negative moment region. The specimens with eccentric and edge columns are those having geometrical eccentricity and whose results are compared with those obtained for specimens with central column to study the effect of column eccentricity. The experimental work included fabrication of specimens and testing them under increasing monotonic gravity loads up to failure. Experimental results demonstrated that the Flexural ultimate load carrying capacity increased by 33%, 37% and 67% for the tested specimens with central, eccentric, and edge column, respectively, when strengthened using CFRP sheets. The cross-sectional analysis was also undertaken to compare the experimental results with those obtained from Canadian Standards for FRP design for buildings.