"ACI 544.8R-16"Development of proper design procedures for fiber-reinforced
concrete (FRC) materials requires use of material tensile and
compressive stress strains that reflect the contribution of fibers to
the post-cracking behavior. While uniaxial tension tests provide
the most fundamental material properties, conducting closed-loop
tension tests are difficult to accomplish; therefore, methods based
on indirect measurement of tensile properties using flexural tests
are typically used.
This report presents the methodologies that are used for data
reduction and presentation of the flexural test results in terms of
an equivalent tensile stress-strain response for FRC materials.
Existing methods for estimating uniaxial tensile stress-strain
response of strain-softening and hardening FRCs from flexural
beam-test data are introduced. Different approaches applied to
beam tests based on elastic equivalent, curve fitting, or back-calculation
of flexural data are introduced. These are divided into two
general categories: elastic equivalent approach or inverse analysis
method. In the elastic equivalent approach, a summary of available
test methods by various code agencies are presented.
Using back-calculation methods, tools based on the finite
element method and analytical closed-form solutions are presented.
An approach is presented that uses closed-form moment-curvature
relationships and obtains load-deflection responses for a beam of
three- or four-point loading. The method is used to obtain equivalent
parametric tensile stress and strain relationships for a variety
of FRC materials. The methods are compared against the available
residual strength and also elastically equivalent residual strengths
obtained by different specimen geometries.
Results for a range of FRC materials studied show the backcalculated
post-peak residual tensile strength is approximately 30
to 37 percent of the elastically equivalent flexural residual strength
for specimens with different fiber types and volume fractions
