A design model for fibre reinforced concrete beams pre-stressed with steel and FRP bars

Composites Part B: Engineering

2016

a b s t r a c tThe 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.

Section: Numerical Simulationmentioning

confidence: 99%

Flexural strengthening of reinforced low strength concrete slabs using prestressed NSM CFRP laminates

Hosseini

Dias

Composites Part B: Engineering

2016

“…By applying the principle of virtual work, the mid-span deflection of the beam for the kth loading step d k ð Þ is obtained, resulting a P k À d k point of the force-deflection response of the beam [29].…”

Section: Evaluation Of Force-deflection Relationshipmentioning

confidence: 99%

“…Numerical approach to determine the force-deflection response of statically determinate beams failing in bending[29].…”

mentioning

confidence: 99%

A model to simulate the moment–rotation and crack width of FRC members reinforced with longitudinal bars

Taheri

Salehian

2015

Engineering Structures

Self Cite

a b s t r a c tThe present work describes a model for the determination of the moment-rotation relationship of a cross section of fiber reinforced concrete (FRC) elements that also include longitudinal bars for the flexural reinforcement (R/FRC). Since a stress-crack width relationship ðr-wÞ is used to model the post-cracking behavior of a FRC, the r-w directly obtained from tensile tests, or derived from inverse analysis applied to the results obtained in three-point notched beam bending tests, can be adopted in this approach. For a more realistic assessment of the crack opening, a bond stress versus slip relationship is assumed to simulate the bond between longitudinal bars and surrounding FRC. To simulate the compression behavior of the FRC, a shear friction model is adopted based on the physical interpretation of the post-peak compression softening behavior registered in experimental tests. By allowing the formation of a compressive FRC wedge delimited by shear band zones, the concept of concrete crushing failure mode in beams failing in bending is reinterpreted. By using the moment-rotation relationship, an algorithm was developed to determine the force-deflection response of statically determinate R/FRC elements. The model is described in detail and its good predictive performance is demonstrated by using available experimental data. Parametric studies were executed to evidence the influence of relevant parameters of the model on the serviceability and ultimate design conditions of R/FRC elements failing in bending.

“…Previous work [10] shows that, using a cross section layered model that takes into account the constitutive laws of the intervening materials, and the kinematic and the equilibrium conditions, the deformational behavior of structural elements failing in bending can be predicted from the moment-curvature relation, M-χ, of the representative cross sections of these elements, using the algorithm described elsewhere [23,24].…”

Section: Numerical Simulationmentioning

confidence: 99%

Behavior of RC beams flexurally strengthened with NSM CFRP laminates

Dias

Janwaen

2018

Composite Structures

An experimental program was carried out to investigate the behavior of RC beams flexurally strengthened using the NSM technique with CFRP laminates. Four beams were tested, a reference beam without CFRP, and three beams flexurally strengthened using different percentage of laminates. The experimental results show that NSM CFRP laminates is an effective solution to increase cracking, yielding and maximum loads of beams failing in bending. Furthermore, the high tensile strength of the CFRP was effectively mobilized. By increasing the CFRP percentage, the load carrying capacity of the NSM beams increased, while the ductility level decreased. Taking into account the experimental results, the predictive performance of the analytical formulation proposed by the ACI was assessed considering two methodologies to determine the maximum strain that can be applied to the CFRP: i) the ACI proposal; ii) the equation proposed by Barros et al. (2007). ACI formulation provides safe results by using both methodologies, but the Barros et al. equation ensures better predictions. A numerical strategy was used to evaluate the load-deflection relationship of the tested beams and to highlight the influence of the longitudinal bars percentage, the CFRP percentage and the concrete strength on the NSM flexural strengthening effectiveness of RC beams.