Simulation of Tension Behavior of Reinforced Concrete Members Strengthened with CFS by Using RBSM (original) (raw)
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Uniaxial Tension Behavior of Reinforced Concrete Members Strengthened with Carbon Fiber Sheets
Journal of Composites for Construction, 2011
This paper presents numerical simulation to the tension behaviour of reinforced concrete (RC) members strengthened with externally bonded Carbon Fiber Sheets (CFS) by using two dimensional Rigid Body Spring Model (RBSM) ([1] and [2]). A non-linear reinforced concrete model strengthened by CFS, with bond-slip models and bond deterioration models to simulate both the steel reinforcement bar-concrete interface and the CFS-concrete interface were applied in the RBSM numerical code. It is reported that the RBSM analysis can represent the experimentally observed phenomena very well.
2009
This paper presents numerical simulation of the tension behaviour of reinforced concrete (RC) members strengthened with externally bonded carbon fiber sheets (CFS) by using two dimensional (2D) rigid body spring model (RBSM). A non-linear RC model strengthened with CFS with bond-slip relations to model the concrete, steel reinforcement interface and concrete, externally bonded CFS interface, and simple models for bond deterioration due to cracking was embedded in the RBSM code that was developed by the authors. Comparison between the RBSM prediction and experimental results shows good agreement. The CFS has shown significant change in the bond stress and average stress of steel reinforcing bar and concrete. In addition the CFS has reduced the crack spacing and gave good crack width control.
Tension-Stiffening Model for Steel Fiber-Reinforced Concrete Containing Conventional Reinforcement
ACI Structural Journal, 2013
The tensile behavior of fiber-reinforced concrete (FRC) members co-reinforced with conventional deformed reinforcing bar (R/FRC members) is analytically investigated in regards to tensile stresses developed in the reinforcing bars, tensile stresses induced in the steel fibers bridging a crack, and the bond mechanism between the reinforcing bar and the concrete matrix. A tension-stiffening model for R/FRC members is developed through an analytical parametric study using a crack analysis procedure that considers the tensile behavior due to the steel fibers and the bond stress-slip relationship between the reinforcing bar and the concrete matrix. With the proposed model, the local yielding of reinforcing bars at a crack can be realistically simulated, enabling reasonably accurate predictions of the tensile behavior of R/FRC members. Analysis results obtained from the proposed model show good agreement with the test results measured by previous researchers.
2007
The basic aim of this paper is to present a preliminary study of the behavior of concrete beams under compression and a flexural stresses, both reinforced with carbon fibers. In each research, theoretical formulations, experimental results and numerical methodology using the finite element methods are presented. To simulate numerically the rupture of the concrete speciments, the adequate parameters are considered to define the rupture surface of the Drucker-Prager criterion for structural concrete elements in higher tensions. For the flexural beam simulation, the Willam-Warnke criterion is applied. In the end of this paper numerical results are presented to conclude this research.
Finite Element Modeling of Reinforced Concrete Beams Strengthened with Carbon Fiber Composites
This paper presents the results of a comparison between a finite element model and experimental data of reinforced concrete beams strengthened with carbon fiber reinforced plastics. For the experimental program, simply supported beams, with 12 x 20 cm cross section and 2.25 m long span were tested. These beams have been submitted to short-term static loading tests from which it has been possible to evaluate the stresses and strains, the displacements, the crack widths and the failure mode. Strains gauges glued to the composite surface allowed the analysis of the behavior at the interface. The tensile and shear stresses at interface could be estimated. The numerical model consisted of a nonlinear finite element model for the flexure-shear response. The concrete was represented through plane stress isoparametric, eight nodes, finite elements. The concrete two-dimensional constitutive law was based on the orthotropic model proposed by Darwin. The concept of uniaxial equivalent strain and the two-dimensional failure criterion of Kupfer and Gerstle were adopted. The reinforcement was represented through an embedded model. Each steel bar was considered as a more rigid line inside of the concrete element, which just resists to axial efforts. The model includes a special interface element to simulate the bond between concrete and the external composite plate which is represented by truss elements.
Materials
This study investigates the mechanical behavior of steel fiber-reinforced concrete (SFRC) beams internally reinforced with steel bars and externally bonded with carbon fiber-reinforced polymer (CFRP) sheets fixed by adhesive and hybrid jointing techniques. In particular, attention is paid to the load resistance and failure modes of composite beams. The steel fibers were used to avoiding the rip-off failure of the concrete cover. The CFRP sheets were fixed to the concrete surface by epoxy adhesive as well as combined with various configurations of small-diameter steel pins for mechanical fastening to form a hybrid connection. Such hybrid jointing techniques were found to be particularly advantageous in avoiding brittle debonding failure, by promoting progressive failure within the hybrid joints. The use of CFRP sheets was also effective in suppressing the localization of the discrete cracks. The development of the crack pattern was monitored using the digital image correlation method. As revealed from the image analyses, with an appropriate layout of the steel pins, brittle failure of the concrete-carbon fiber interface could be effectively prevented. Inverse analysis of the moment-curvature diagrams was conducted, and it was found that a simplified tension-stiffening model with a constant residual stress level at 90% of the strength of the SFRC is adequate for numerically simulating the deformation behavior of beams up to the debonding of the CFRP sheets.
Advances in Structural Integrity, 2017
In practical terms, repair and strengthening of reinforced concrete structures with composite materials is an issue of great importance. However, how this strengthening affects the strength of reinforced structures has not been adequately justified. The specific features of the deformation behavior of strengthened structures are mainly determined by the debonding of the composite from the concrete surface. Experimental data describing the debonding process are practically absent. This paper presents the results of experimental studies of deformation processes taking place in bending reinforced beams strengthened with carbon fiber sheets. A thermography technique was used to detect the debonding in the examined structures. The results obtained made it possible to evaluate the effect of the strengthening of carbon fiber sheets on the deformation process and bearing capacity of reinforced concrete beams.
Journal of Materials in Civil Engineering, 2004
The paper is devoted to the cracking and deformability analysis of steel reinforced concrete beams strengthened with externally bonded carbon fiber reinforced polymer (CFRP) sheets. A theoretical nonlinear model, derived from a cracking analysis founded on slip and bond stresses, is adopted. The model takes into account both the tension stiffening effects of the concrete and the force transfer between the concrete and the CFRP sheet at the interface. A local bond-slip law-defined by experimental tests, carried out on concrete specimens strengthened with CFRP sheets-is adopted in the model. The slip between the concrete and the traditional steel bars is also considered. Theoretical predictions, in terms of crack width, curvature, and deflections, are compared with available experimental results and predictions of traditional models, usually adopted for design purposes. Obtained results are presented and discussed.
Constitutive Model for Steel Fibre Reinforced Concrete in Tension
2013
In order to represent the ductile tensile behaviour of steel fibre reinforced concrete (SFRC), the Diverse Embedment Model (DEM) was recently developed, accounting for both the random distribution of fibres and the pull-out behaviour of fibres. Although the DEM shows good agreement with test results measured from uniaxial tension tests, it entails a double numerical integration which complicates its implementation into computational models and software developed for the analysis of the structural behaviour of SFRC members. In this paper, the DEM is simplified by eliminating the double numerical integration; thus, the Simplified DEM (SDEM) is derived. In order to simplify the DEM, only fibre slip on the shorter embedded side is taken into the account of the fibre tensile stress at a crack, while coefficients for frictional bond behaviour and mechanical anchorage effect are incorporated to prevent overestimation of the tensile stress attained by fibres due to the neglect of fibre slip...
Purpose – The purpose of this paper is to present a new bond slip model for reinforced concrete structures. It consists in an interface element (3D) which represents the interface between concrete (modeled in 3D) and steel, modeled using 1D truss elements. Design/methodology/approach – The formulation of the interface element is presented and verified through a comparison with an analytical solution on an academic case. Finally, the model is compared with experimental results on a reinforced concrete tie. Findings – Contrary to the classical perfect or “no-slip” relation which supposes the same displacement between steel and concrete, the proposed model is able to reproduce both global (force-displacement curve) and local (crack openings) results. Originality/value – The proposed approach, applicable to large-scale computations, represents a valuable alternative to the no-slip relation hypothesis to correctly capture the crack properties of reinforced concrete structures.