Behavior of Concrete Columns Confined by Fiber Composites
01 May 1997-Journal of Structural Engineering-asce (American Society of Civil Engineers)-Vol. 123, Iss: 5, pp 583-590
TL;DR: In this paper, a series of uniaxial compression tests on concrete-filled fiber reinforced plastic (FRP) tubes are compared with the available confinement models in the literature.
Abstract: External confinement of concrete by means of high-strength fiber composites can significantly enhance its strength and ductility as well as result in large energy absorption capacity. The confinement mechanism may include fiber-wrapping of existing columns as a retrofitting measure or encasement of concrete in a fiber reinforced plastic (FRP) tube for new construction. Proper design of such hybrid columns, however, requires an accurate estimate of the performance enhancement. Current design methods use simple extension of the models developed for conventional reinforced concrete columns. Results from a series of uniaxial compression tests on concrete-filled FRP tubes are compared with the available confinement models in the literature. The present study indicates that these models generally result in overestimating the strength and unsafe design. The study also shows a unique characteristic of confinement with fiber composites in that, unlike steel, FRP curtails the dilation tendency of concrete, as it re...
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TL;DR: In this paper, a new design-oriented stress-strain model is proposed for concrete confined by FRP wraps with fibres only or predominantly in the hoop direction based on a careful interpretation of existing test data and observations.
1,161 citations
Cites background from "Behavior of Concrete Columns Confin..."
...…and Teng 2003; Berthet et al. 2006; Harajli 2006; Saenz and Pantelides 2007; Wu et al. 2007; Youssef et al. 2007) and analysis-oriented models (e.g. Mirmiran and Shahawy 1997; Spoelstra and Monti 1999; Fam and Rizkalla 2001; Chun and Park 2002; Harries and Kharel 2002; Marques et al. 2004; Binici…...
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TL;DR: In this article, a simple model is presented to predict the complete bilinear stress-strain response of fiber-reinforced plastic (FRP) confined concrete columns in both axial and lateral directions.
Abstract: Fiber-wrapping or encasement of concrete in fiber-reinforced plastic (FRP) shells significantly enhances strength and ductility of concrete columns. However, design of such hybrid systems requires an accurate estimate of the performance enhancement due to the confinement mechanism. Current design procedures are simple extensions of the models developed for conventional reinforced concrete columns. Previous studies have demonstrated that such models may not be conservative for FRP-encased concrete. A simple model is presented to predict the complete bilinear stress-strain response of FRP-confined concrete in both axial and lateral directions. The model is based on correlation between the dilation (expansion) rate of concrete and the hoop stiffness of the restraining member. The parameters of the model are directly related to the material properties of the FRP shell and the concrete core. The predicted stress-strain curves compare favorably with the results of the present study, as well as tests by others on both fiber-wrapped and FRP-encased concrete columns.
763 citations
TL;DR: In this paper, axial compression test results of 27 concrete cylinders confined by carbon fiber reinforced polymer composite jackets were described, and the failure of the confined concrete was dominated by the rupture of the jacket at an average strain much smaller than the ultimate strain obtained from tension tests of flat coupons.
Abstract: This paper describes axial compression test results of 27 concrete cylinders confined by carbon fiber reinforced polymer composite jackets. The experimental parameters include plain concrete compressive strength and the thickness of the composite jacket. It is found that the carbon fiber composite jacketing can significantly increase the compressive strength and ductility of concrete. The test results indicate that concrete strength and confinement modulus, defined as the ratio of transverse confinement stress and transverse strain, are the most influential factors affecting the stress-strain behavior of confined concrete. The failure of the confined concrete was dominated by the rupture of the jacket at an average strain much smaller than the ultimate strain obtained from tension tests of flat coupons. In order to describe the main mechanical features of the confined concrete, a simple bilinear stress-strain model is suggested based on the theory of elasticity and minimum number of empirical equations de...
661 citations
Cites background from "Behavior of Concrete Columns Confin..."
...Higher Plain concrete 1-layer 2-layer 3-layer teraction mechanisms between the composite jackets and the confined concrete is still limited (Picher et al. 1996; Hosotani et al. 1996; Mirmiran and Shahawy 1997)....
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References
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TL;DR: In this paper, a stress-strain model for concrete subjected to uniaxial compressive loading and confined by transverse reinforcement is developed for concrete sections with either spiral or circular hoops, or rectangular hoops with or without supplementary cross ties.
Abstract: A stress‐strain model is developed for concrete subjected to uniaxial compressive loading and confined by transverse reinforcement. The concrete section may contain any general type of confining steel: either spiral or circular hoops; or rectangular hoops with or without supplementary cross ties. These cross ties can have either equal or unequal confining stresses along each of the transverse axes. A single equation is used for the stress‐strain equation. The model allows for cyclic loading and includes the effect of strain rate. The influence of various types of confinement is taken into account by defining an effective lateral confining stress, which is dependent on the configuration of the transverse and longitudinal reinforcement. An energy balance approach is used to predict the longitudinal compressive strain in the concrete corresponding to first fracture of the transverse reinforcement by equating the strain energy capacity of the transverse reinforcement to the strain energy stored in the concret...
6,261 citations
Book•
01 Jan 1982
TL;DR: In this article, some basic properties of concrete and steel are discussed and failure criteria of concrete elasticity and failure of brittle fracture models are discussed. But the authors focus on the failure criteria and not the elasticity of the model.
Abstract: PrefaceNotationPart 1 - Basic Concepts and ExperimentsChapter 1 - IntroductionChapter 2 - Some Basic Properties of Concrete and SteelPart 2 - Concrete Elasticity and Failure CriteriaChapter 3 - Linear-Elastic Brittle-Fracture ModelsChapter 4 - Nonlinear-Elastic Fracture ModelsChapter 5 - Failure Criteria of ConcretePart 3 - Concrete Plasticity: Theory and ApplicationChapter 6 - Elastic Perfectly Plastic Fracture ModelsChapter 7 - Limit Analysis of Perfect PlasticityChapter 8 - Elastic-Hardening Plastic-Fracture ModelsChapter 9 - Numerical Implementation of Elastoplastic Fracture ModelsAuthor IndexSubject Index
1,043 citations
"Behavior of Concrete Columns Confin..." refers background in this paper
...In a triaxial state of stress, volumetric strain £v (or dilatation) is defined as the volume change per unit volume (Chen 1982)...
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...From the pioneering work of Considire (1903), who introduced spiral reinforcement in concrete columns, researchers have attempted to develop a generalized model to quantify the effects of confinement on strength and ductility of concrete....
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...90/:, after which the direction of volume change is reversed, resulting in an inelastic volume expansion or dilatancy near or at t:, and an unstable expansion beyond the peak strength (Chen 1982). Replotting test data from Ahmad and Shah (1982) confirms that unstable dilatancy also occurs for steelencased concrete when steel yields....
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...90/:, after which the direction of volume change is reversed, resulting in an inelastic volume expansion or dilatancy near or at t:, and an unstable expansion beyond the peak strength (Chen 1982)....
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Book•
01 Jan 1928
TL;DR: In this article, a study of concrete specimens loaded in compression in one, in two, or in three directions at right angles to each other by means of fluid pressures was carried out.
Abstract: The investigation has been carried out in two parts: (1) a study of concrete specimens loaded in compression in one, in two, or in three directions at right angles to each other by means of fluid pressures, and (2) a study of plain and spirally reinforced concrete compression specimens loaded in one direction in the usual manner. The bulletin contains the results of the first group of tests (series nos. 2, 3A, and 3B) ... It is planned to report the second group of tests (series no. 1) in a later bulletin [i.e. Bulletin no. 190].
833 citations
TL;DR: In this article, an analytical model is proposed to construct a stress-strain relationship for confined concrete, which consists of a parabolic ascending branch, followed by a linear descending segment.
Abstract: An analytical model is proposed to construct a stress‐strain relationship for confined concrete. The model consists of a parabolic ascending branch, followed by a linear descending segment. It is based on calculation of lateral confinement pressure generated by circular and rectilinear reinforcement, and the resulting improvements in strength and ductility of confined concrete. A large volume of test data, including poorly confined and well‐confined concrete was evaluated to establish the parameters of the analytical model. Confined concrete strength and corresponding strain are expressed in terms of equivalent uniform confinement pressure provided by the reinforcement cage. The equivalent uniform pressure is obtained from average lateral pressure computed from sectional and material properties. Confinement by a combination of different types of lateral reinforcement is evaluated through superposition of individual confinement effects. The descending branch is constructed by defining the strain correspond...
695 citations
"Behavior of Concrete Columns Confin..." refers background in this paper
...More recently, Saatcioglu and Razvi (1992) suggested the following coefficient based on the test data from Richart et al....
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TL;DR: In this article, a new technique for seismic strengthening of concrete columns is presented, which requires wrapping thin, flexible high-strength fiber composite straps around the column to improve the column's ductility and strength.
Abstract: Bridge failures in recent earthquakes such as the 1989 Loma Prieta earthquake have attracted the attention of the bridge engineering community to the large number of bridges with substandard seismic design details. Many concrete columns in bridges designed before the new seismic design provisions were adopted have low flexural ductility, low shear strength, and inadequate lap length for starter bars. These problems, compounded by flaws in the design of structural systems, have contributed to the catastrophic bridge failures in recent earthquakes. In this paper, a new technique for seismic strengthening of concrete columns is presented. The technique requires wrapping thin, flexible high-strength fiber composite straps around the column to improve the confinement and, thereby, its ductility and strength. Analytical models are presented that quantify the gain in strength and ductility of concrete columns externally confined by means of high-strength fiber composite straps. A parametric study is conducted to examine the effects of various design parameters such as concrete compressive strength, thickness and spacing of straps, and type of strap. The results indicate that the strength and ductility of concrete columns can be significantly increased by wrapping high-strength fiber composite straps around the columns.
484 citations
"Behavior of Concrete Columns Confin..." refers methods in this paper
...When the model is applied to FRPs, the energy approach generates a failure stress much lower than that calculated from the equilibrium of forces (Saadatmanesh et al. 1994; Mirmiran and Shahawy 1996)....
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