ABSTRACT
Abstract Tensile tests on FRP bars are affected by local stress concentrations near the grips. These grip effects result in progressive failure of the fibers within the rebar which in turn results in measured ultimate properties lower than expected. Another consequence is an apparent size effect, with lower strengths recorded for larger bar diameters. In an attempt to determine an appropriate anchoring mechanism, a simple clamp grip is first developed in which the lateral pressure can be controlled. A wrapping systems at the bar ends is then analyzed numerically via a finite element model and tested. The analyses show the existing stress localizations in the bars and the effects of the end wraps. Tests using the clamp grips showed increased measured strengths when compared to the standard ASTM D3916 tension test. Wraps with high ultimate elongation and low uniaxial stiffness showed further improvement and forced the failure away from the grips in half of the tests. Keywords: Fiber reinforced plastics, grips, reinforcing bars
1 Introduction Fiber reinforced plastic (FRP) rods are currently being used as reinforcing bars and prestressing strands in reinforced/prestressed concrete structures, mostly in Japan [1,2], Europe [3,4], and in the United States [5,6,7]. For FRP tendons, the end anchorage has typically been the weakest link. To determine the tensile strength of both tendons and reinforcing bars, traditional gripping mechanisms have proven unsatisfactory as the induced stress concentrations near the grips have resulted in premature failure. The objective of this paper is to analyze two types of anchorages for FRP rods, namely the clamp and the end wrap.
