Title:
Experimental and Analytical Modeling of Concrete-Filled Fiber-Reinforced Polymer Tubes Subjected to Combined Bending and Axial Loads
Author(s):
Amir Fam, Bart Flisak, and Sami Rizkalla
Publication:
Structural Journal
Volume:
100
Issue:
4
Appears on pages(s):
499-509
Keywords:
beam; column; concrete; confinement; fiber-reinforced polymer.
DOI:
10.14359/12659
Date:
7/1/2003
Abstract:
This paper presents test results of an experimental program and proposes an analytical model to describe the behavior of concrete-filled fiber-reinforced polymer (FRP) tubes subjected to combined axial compression loads and bending moments. The experimental program included 10 specimens subjected to eccentric axial loads, two specimens tested under concentric axial loads, and two specimens tested in bending. Glass FRP (GFRP) tubes with two different laminate structures were considered. Axial load/bending moment interaction curves are presented. The paper presents an analytical model that accounts for variable confinement of concrete as a result of the gradual change of the biaxial state of stresses developed in the tube as the eccentricity changes. The model uses the classical lamination theory for the FRP tubes and accounts for their gradual reduction of stiffness as a result of the progressive failure of different FRP layers. A parametric study was conducted to evaluate the effects of diameter-to-thickness ratio and laminate structure of the tube, including different fiber proportions in the axial and hoop directions. The study evaluated the confinement as affected by the eccentricity of the applied axial load as well as the influence of the FRP laminate structure. Research findings indicated that the interaction curves are significantly affected by both the laminate structure and diameter-to-thickness ratios of the tubes. The contribution of confinement—resulting from increasing the ratio of fibers in the hoop direction—to the overall axial strength of concrete-filled FRP tubes seems to be significant for thin-walled tubes only.