Modeling of Tension Stiffening Behavior in FRP‐Strengthened RC Members Based on Rigid Body Spring Networks

Abstract

Allowing for the tension stiffening effects resulting from the bond between steel reinforcement and surrounding concrete leads to effective deformation analysis of reinforced concrete (RC) members when using a nonlinear finite element analysis modeled on the smeared crack concept. Nowadays, externally bonded fiber reinforced polymer (FRP) composites are widely used for strengthening existing RC structures. However, it remains unclear to what extent the tension stiffening of postcracking concrete is quantitatively influenced by the addition of FRP composites, as a result of the bond between the FRP and the concrete substrate. This article presents a discrete model, which is based on rigid body spring networks (RBSN), for investigating the tension stiffening behavior of concrete in FRP‐strengthened RC tensile members. A two‐parameter fracture energy‐based model was deployed to represent the bond‐slip behavior of the FRP‐to‐concrete interface. The reliability of the RBSN model was verified through comparisons with previous test results. Further parametric analysis indicates that the tension stiffening of concrete is hardly influenced by the addition of FRP composites before the yield of steel reinforcement has occurred although concrete crack patterns and crack widths may be influenced by the bond‐slip behavior of the FRP‐to‐concrete interface.

Strengthening and Rehabilitation of Reinforced Concrete Slabs with Carbon‐Fiber Reinforced Polymers Using a Refined Bond Model

“…When comparing the calculated and measured values for the CFRP strain, it can be noticed that there is a good match at the start. But on the verge of the failure, there is a bigger difference between the calculation and the measurement, because there is higher tension stiffening (see also Dai et al, 2012). The measured value is about 10% lower than the calculated one.…”

Micromechanical modeling of tension stiffening in FRP-strengthened concrete elements

“…Extensive experimental, analytical and numerical studies have shown the effectiveness of this technique in improving the strength and stiffness of RC elements. Although the effect of FRP application and FRP-concrete bond on the ultimate limit state (ULS) behavior of strengthened elements have been extensively studied [1,2], their effect on the service limit state (SLS) behavior and cracking has received less attention [3][4][5][6][7].…”

“…The available results show FRP application affects the stiffness and deformation of the strengthened elements and leads to reduction of crack spacing and width [5,8]. The analytical and numerical investigations on this subject are also still limited [3,7,9,10] and comprehensive models describing the tension stiffening with detailed consideration of micromechanical mechanisms are scarce. As for macro-modeling, suitable constitutive models, as the main inputs of smeared crack modeling approaches, are not available yet.…”

“…Several models have been proposed for modeling the average tensile behavior of reinforcing bars and concrete in RC elements [12][13][14][15][16][17], while the number of recent studies on this subject shows 3 there are still debates on the accuracy of the previous models [4,[18][19][20][21]. Most of the available formulations for prediction of the crack spacing and width have been found to produce controversial results depending on the geometry of the specimens and reinforcement type [21].…”

In‐Plane Displacement and Strain Image Analysis

“…Sutton (Ke et al., ; Reu et al., ; Sutton et al., , ) started to study image correlation techniques for photogrammetry in the early 1980s until now, with several publications in two‐ and three‐dimensional Digital Image Correlation (DIC; Sutton et al., ). Since then photogrammetry has been increasingly used as an additional tool in various engineering tests such as load tests, monitoring structures, crack measurements (Dai et al., ; Huang et al., ; Iyer and Sinha, ; Nishikawa et al., ; Park et al., , ).…”