Three-Dimensional Nonlinear Finite-Element Analysis of Prestressed Concrete Beams Strengthened in Shear with FRP Composites

Abstract

Nonlinear finite-element (FE) analysis was carried out to investigate the structural response of prestressed concrete (PC) beams strengthened with fiber reinforced polymer (FRP) composites in shear. Development of the FE model for concrete structures dominated by shear, in particular for FRP-strengthened concrete structures, requires careful consideration in choosing the appropriate elements and constitutive laws to simulate the proper failure mode. The paper presents a new three-dimensional technique to model FRP-strengthened prestressed concrete beams. Most previous work has dealt with two-dimensional analysis of FRP-strengthened reinforced concrete beams. The novel attributes of the proposed model lie in the description of the three-dimensional constitutive material models for each component. The model accounts for the softening behavior of concrete under a triaxial state of stress. A new three-dimensional interface element necessary to capture the debonding failure was proposed. In particular, the effect of the out of plane stress behavior of the FRP-concrete interface, which is currently unavailable through experimental measurements, was carefully evaluated. The use of mechanical anchors to improve the bond behavior was properly simulated. In addition, the prestressing operation and precracking effects were also simulated in the model through a phased analysis technique, which makes it possible to predict the response with respect to the time-dependent behavior of elements and materials. The FE model developed in this study was calibrated through comparison with test results. This paper reports not only on the fundamental investigation of the strengthening effect of FRP composites for PC beams but also on the identification of the damage mechanisms and the progression of failure. The model was shown to provide a good level of correlation with experimental data, and could therefore be used to conduct extensive parameter studies.