Fiber reinforced plastic (FRP) has in recent years emerged as an alternative reinforcement for structural concrete. The properties that make FRP appealing to the construction industry include its resistance to electro-chemical corrosion, high strength-to-weight ratio, and electrical insulation. An efficient use of FRP is in the form of concrete-filled tubes, where the tube not only protects the concrete against environmental factors, but also provides confinement and external reinforcement. Since use of fiber composites for confining concrete is relatively new, analytical work in this area is limited to the models that were originally developed for transverse steel reinforcement. However, it has been shown that such models overestimate the strength of FRP-confined concrete, and result in unsafe design This study is focused on developing a nonlinear finite element model for the analysis of FRP-confined concrete. Solid elements are used for the concrete core, along with a non-associative Drucker-Prager type plasticity, which takes into account the pressure sensitivity of the material. The parameters used to model the concrete are cohesion, angle of internal friction, and the dilatancy angle. The jacket is modeled by linear-elastic membrane shell elements. A parametric program was developed within the ANSYS® software to automatically generate the mesh for various geometric shapes and material properties. A sensitivity analysis was conducted to determine the optimum number of elements required in the mesh. The model was validated against previous experiments at UCF. The stress-strain curves compared favorably with the test data. The model was also used for square sections to compare their confinement effectiveness with that of circular sections. The analysis, much the same as the experiments, showed stress concentrations around the comers. The stress concentration and the confinement effectiveness both depend on the comer radius of the section. Finally, the model was used to examine the plastic deformations of concrete filled FRP tubes under cyclic loading, i.e., unloading and reloading in compression.
Master of Science (M.S.)
College of Engineering
Civil and Environmental Engineering
Structures and Foundations
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Length of Campus-only Access
Masters Thesis (Open Access)
Dissertations, Academic -- Engineering; Engineering -- Dissertations, Academic
Zagers, Kenneth T., "Nonlinear Modeling of Concrete-filled FRP Tubes Using the Finite Element Method" (1998). Retrospective Theses and Dissertations. 2593.