Concrete columns encased in fiber-reinforced polymer (FRP) tubes offer an attractive solution to enhance behavior of concrete in terms of strength as well as ductility. Analytical models for development of stress-strain curves for concrete confined with FRP are proposed in this paper. The predicted stress-strain curves for confined concrete using the proposed models are compared with those of tests for concrete specimens confined with FRP. It is demonstrated that the proposed models predict the stress-strain behavior of confined concrete very well. Based on the confidence gained in the proposed models, the effects of using different fibers, the presence of voids, and the number of layers are established.

Design and detailing requirements for composite concrete beams are specified in clause 17.5 of building code 318 of the American Concrete Institute. These requirements rely on monolithic action of the entire cross section to develop flexural and shear resistance, and for deflection control. Detailing of the interface between the precast web and cast-in-place flange to resist horizontal shear in a composite concrete beam is crucial in developing a monolithic action for such beams. This paper presents the results of recent research on the behavior of composite concrete beams with a smooth interface. Current provisions of the American Concrete Institute's code on flexural strength, shear strength, and deflection characteristics are found to be satisfactory. However, the code clauses dealing with horizontal shear are found to be very conservative. Based on test results, an equation to represent the shear transfer strength of a smooth interface is developed. Suitable suggestions are made for consideration duri...

Fiber reinforced polymer (FRP) composite bars are suitable substitutes for steel reinforcement in structural concrete because of their light weight and high specific strength and stiffness. Sustained load on FRP composites over the entire service life of the structure can cause failure by creep rupture at loads much smaller than those corresponding to static transient loads. Creep rupture test methods used by several researchers are presented, and a suitable loading arrangement and test method were selected for this study. The creep rupture properties of basalt FRP bars were determined using sustained loading applied to the test specimens simultaneously with an alkaline solution at an elevated temperature. The tests were based on the method specified by the American Concrete Institute (ACI) in a standard. The ultimate creep rupture strength coefficients for basalt FRP bars were determined to be approximately 18% for 50 year service life and 28% for 5 year service life. The corresponding one millio...