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Title: Modeling of Near-Surface-Mounted Fiber-Reinforced Polymer Strips to Concrete

Author(s): Solmaz Afzali, Hamidreza Alinejad, Kourosh Nasrollahzadeh, and Thomas H.-K. Kang

Publication: Structural Journal

Volume: 118

Issue: 5

Appears on pages(s): 3-16

Keywords: bond stress-slip curve; fiber-reinforced polymer (FRP); finite element (FE) method; modeling; near-surface-mounted FRP; pullout test

DOI: 10.14359/51732866

Date: 9/1/2021

Near-surface-mounted (NSM) fiber-reinforced polymer (FRP) is a strengthening method for reinforced concrete (RC) structures that relies on the bond between FRP strip/rod embedded in an epoxy-filled saw-cut groove and the concrete substrate. The bond stress is known to relate to the slip along their interface. This paper aims to propose a technique for modeling the bond between NSM FRP and concrete for the specimens, in which failure occurred at the concrete-adhesive or adhesive-FRP interface, or by rupture of the FRP, using the finite element (FE) method. The FE analysis is more accurate in predicting the bond capacity of the joint and simple to use for modeling the interactions in comparison to the existing bond models. The proposal uses a three-dimensional (3-D) FE model, and simulation results are verified by the experimental results of direct pullout tests of 25 specimens done by the other researchers. The form of the bond stress-slip curve considered in the proposed model is bilinear. A comparison of the strain distribution along the bond length at different loading stages with avail-able experimental values showed that the proposed model accurately predicts this distribution. A parametric study on the initial stiffness of the bond stress-slip curve revealed that a value of 10 times the epoxy elastic modulus (Ee) to the thickness of the epoxy layer between FRP and concrete (te) is appropriate. In addition, a parametric study on bond length disclosed that the developed model can capture effective bond length—that is, the length beyond which bond strength no longer increases.