Tensile and Nondestructive Testing of FRP Bars.
Tensile and Nondestructive Testing of FRP Bars.
(1290 K)
Castro, P. F.; Carino, N. J.
Journal of Composites for Construction, Vol. 2, No. 1,
17-27, February 1998.
Keywords:
building technology; fiber reinforced plastic; modulus
of elasticity; nondestructive testing; reinforcing bars;
reasonant frequency; statistical methods; tensile test;
ultrasonic pulse velocity
Abstract:
An exploratory study was carried out to support the
development of standard test methods for fiber
reinforced plastic (FRP) bars for use as concrete
reinforcement. The principal objectives were to develop
a simple, economical, and effective system to permit
tensile loading of the bars in a universal test machine;
to evaluate the influence of the
free-length-to-bar-diameter ratio on the measured
tensile strength; and to explore the potential of
measuring the elastic modulus using available
nondestructive test methods. A successful system for
applying tensile load was developed. The ends of a bar
were embedded in steel tubes using a high-strength
gypsum cement mortar. The bars were loaded by gripping
the tubes in the conventional wedge friction grips of a
tensile testing machine. No statistically significant
influence of the free-length-to-diameter ratio was
observed for ratios varying between 40 and 70. However,
large within-test variability of tensile strength was
observed. Dynamic modulus of elasticity was determined
using two stress-wave propagation methods: ultrasonic
pulse velocity and resonant frequency. The dynamic
values compared favorably with static values obtained
from tensile stress-strain curves. Recommendations are
provided for additional studies to support the
development of standard test methods.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899