Behavior of damaged and undamaged concrete strengthened by carbon fiber composite sheets

İlki, Alper; Kumbasar, Nahit

doi:10.12989/sem.2002.13.1.075

Cited by 74 publications

(33 citation statements)

References 13 publications

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“…Therefore, this type of anchorage system can be used to limit the residual displacement (and consequently residual damage). The retrofitted columns behaved similar in terms of strength degradation after the rupture of FRP reinforcement as the specimens tested by Ilki and Kumbasar [46], Bournas and Triantafillou [47], and Vrettos et al [50], where the drift ratios at failure were approximately 2%, 4% and 2.5%, respectively. It is important to note that all significant damage was accumulated at the base of the columns, since the columns were wrapped with CFRP sheets in transverse direction along the full height.…”

Section: Lateral Load-displacement Curves and Failure Modessupporting

confidence: 58%

“…While there are many studies on external confinement of columns or joints [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26], and on flexural retrofit with near surface mounted (NSM) FRP rods or pultruded strips under monotonic loading conditions [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42], only few studies are available on flexural retrofitting using FRPs under repeated loading conditions [43][44][45]. According to the best knowledge of the authors', reversed cyclic flexural behavior of RC members strengthened with longitudinal FRP reinforcement was studied for the first time by Ilki and Kumbasar [46]. More recently, Bournas and Triantafillou [47], Goksu et al [48], Fahmy and Wu [49], Vrettos et al [50], Li et al [51], Goksu et al [52] and Faustino and Chastre [53] also studied this type of behavior.…”

Section: Introductionmentioning

confidence: 99%

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Seismic Behavior of Substandard RC Columns Retrofitted with Embedded Aramid Fiber Reinforced Polymer (AFRP) Reinforcement

et al. 2015

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Many existing reinforced concrete structures were constructed with substandard characteristics. Low quality concrete, poor transverse reinforcement details and insufficient flexural strength are among the most common deficiencies. While substandard structures are in need of retrofitting, particularly in seismic areas, problems such as high costs and disturbance to occupants are major obstacles for retrofit interventions. Fiber reinforced polymers can provide feasible retrofit solutions with minimum disturbance to occupants. In this study, the basic aim is to investigate the flexural seismic performance of substandard reinforced concrete columns retrofitted with embedded longitudinal fiber reinforced polymer reinforcement without increasing the original dimensions of the columns. In the experimental study, the reference and retrofitted columns were tested under constant vertical and reversed cyclic lateral loads. Three different connection methods of aramid fiber reinforced polymer reinforcement to the footing were investigated experimentally. A significant enhancement was obtained in lateral flexural strength through the proposed retrofitting method. Furthermore, it was observed that the cyclic lateral drift capacities of the retrofitted columns were as high as 3%, which can be deemed as quite satisfactory against seismic actions. The comparison of the experimental data with analytical calculations revealed that a conventional design approach assuming composite action between concrete and fiber reinforced polymer reinforcement can be used for flexural retrofit design. Experimental results also demonstrated that strain limit for longitudinal fiber reinforced polymer (FRP) reinforcement should be remarkably lower in case of reversed cyclic loading conditions.

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Section: Lateral Load-displacement Curves and Failure Modessupporting

confidence: 58%

Section: Introductionmentioning

confidence: 99%

Seismic Behavior of Substandard RC Columns Retrofitted with Embedded Aramid Fiber Reinforced Polymer (AFRP) Reinforcement

et al. 2015

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“…Mirmiran and Shahawy [22], Ilki and Kumbasar [23,24], , Shao et al [25], Lam et al [26], Tamuzs et al [27] and Ilki et al [30] tested 150 × 300 mm concrete cylinders confined with unidirectional FRP tubes or wraps under axial stresses. The specimens tested by Mirmiran and Shahawy [22] were confined by glass FRP tubes, and they tested only one of the specimens under cyclic loading.…”

Section: Outline Of Available Cyclic Testsmentioning

confidence: 99%

“…The unconfined concrete compressive strength of the specimens was around 30 MPa. The specimens tested by Ilki and Kumbasar [23,24] under cyclic axial stresses were either pre-damaged or undamaged. The confining material was carbon FRP sheets.…”

Section: Outline Of Available Cyclic Testsmentioning

confidence: 99%

“…For prediction of the seismic performance of structural members externally confined with FRP sheets under seismic excitations, the knowledge on the stress-strain relationship of FRP confined concrete/reinforced concrete members under cyclic loads is essential. Although many researchers examined the behavior of FRP confined concrete under monotonic compression , very few studies are available on the behavior of FRP confined concrete under cyclic axial stresses [22][23][24][25][26][27][28][29][30][31][32][33]. Most of these cyclic tests are on small-size cylinders or prisms, except the specimens tested by Ilki and Kumbasar [24] and Ilki et al [31], which included medium-size specimens with circular and non-circular cross sections.…”

Section: Introductionmentioning

confidence: 99%

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Cyclic Stress–Strain Relationships of FRP Confined Concrete Members

2014

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External confinement of columns of existing reinforced concrete buildings using fiber-reinforced polymer (FRP) composites can significantly increase the ductility and compressive strength of structural members against seismic actions. Therefore, knowledge on the behavior of FRP confined concrete/reinforced concrete members under cyclic stresses is vitally important for realistic prediction of seismic performance of retrofitted structures. In this study, available experimental data on the cyclic stress-strain behavior of FRP confined concrete/reinforced concrete members are evaluated in a comparative manner, and accuracy of several stress-strain models proposed for FRP confined concrete is discussed in terms of prediction of the skeleton curves, as well as the unloading-reloading branches of the cyclic stressstrain relationships of the tested samples. Furthermore, a new model is proposed for the prediction of unloading and reloading branches based on the cyclic tests carried out specifically for this purpose. The predictions of the proposed model and two other available models proposed for cyclic loading are compared with experimental data, and a satisfactory agreement is observed between the predictions and experimental data.

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Axial load behavior of circular and square concrete columns confined with sprayed fiber-reinforced polymer composites

2015

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Many experimental and theoretical investigations have been carried out to study the compressive strength of concrete confined externally with unidirectional fiberreinforced polymer (FRP) composites. These unidirectional FRP(s) include carbon, glass, aramid, polyethylene terephthalate, and polyethylene naphthalates. In this article, the performance of randomly distributed sprayed fiber-reinforced polymer (SFRP) composites on the enhancement of strength and deformability of concrete column through external confinement is investigated. The salient features of SFRP are quick and easy application as well as the uniform tensile properties in all directions. In the present study, 24 small concrete specimens were loaded to failure under the uniaxial compression loading. The study parameters covered SFRP thickness, fiber length, and column sectional shape (circular and square). Test results showed that the external confinement by SFRP is significantly effective to increase the strength and deformability of confined concrete. Based on the experimental results, the performance of existing strength models developed for the unidirectional FRP is assessed to examine its applicability to the SFRP confinement. It is found that none of the existing models is capable of accurately predicting the strength of concrete confined with SFRP. Finally, new strength models based on a linear relationship between confined concrete compressive strength and lateral confining pressure are proposed to predict the compressive strength of circular and square sections. The strengths predicted by the proposed models are found to have a good agreement with experimental results. POLYM. COMPOS., 00:000-000, 2015.

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Behavior of damaged and undamaged concrete strengthened by carbon fiber composite sheets

Cited by 74 publications

References 13 publications

Seismic Behavior of Substandard RC Columns Retrofitted with Embedded Aramid Fiber Reinforced Polymer (AFRP) Reinforcement

Seismic Behavior of Substandard RC Columns Retrofitted with Embedded Aramid Fiber Reinforced Polymer (AFRP) Reinforcement

Cyclic Stress–Strain Relationships of FRP Confined Concrete Members

Axial load behavior of circular and square concrete columns confined with sprayed fiber-reinforced polymer composites

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