SAMPE Journal - January/February 2025 - 37
loaded to 25, 50, 75, and 100% of the service load
calculated for each beam according to American
Concrete Institute 440 (ACI)[4]
. This assumed that
the service load was one third of the beam's nominal
moment capacity. The beams, which had been
designed to fail in tension, were then loaded until
failure to best characterize the performance of the
rebar. Although the beams' ultimate strengths were
slightly lower than expected, they were reasonably
predicted using ACI 440, thus overall performance
supported research continuation.
Following the initial TP rebar tests were
simple tests of the long-fiber thermoplastic bars
produced via the CFM. These involved tensile
testing and bending demonstrations of the new
bars. The tension testing was performed with
knurled aluminum clamps bolted together within
a universal testing machine. Despite the grip
failures induced from this test method, tensile
failure stresses in the rebar were higher than those
observed during the prototype rebar beam testing,
which helps validate the initial manufacturing
capabilities of the CFM. The bars were also
subjected to field bending, this time using a pipe as
the mandrel. Furthermore, as seen in Figure 12, a
twist was applied to the bar during bending, which
eliminated buckling of the fibers on the inner bend
radius.
These rods, after rotary stamp forming of shear
lugs to become rebar, underwent modified ASTM
D7205 tensile testing[29]
, ASTM D7913 pullout
testing[30], and concrete beam testing. Pictures
from the tension testing and beam testing are
presented in Figure 13. Using longer rebar, the
concrete beams were of structural scale at 6.1 m
in length with a typical span to depth ratio of 15:1
and designed to AASHTO[3]
. Two pairs of beams
were made with sets of two and four rebar to
provide tensile reinforcement, using a structural
concrete mix typical for bridge decks with a target
compressive strength of 27.6 MPa. Each of the
beams were tested in four-point bending and
failed in tension, reaching on average 103% of
Figure 12. CFM pultruded bar formed with a twisting method to eliminate
fiber buckling.
their predicted capacity. They also exhibited a clear
doubling in moment capacity with the doubling
of concrete reinforcement. These results indicated
good performance of the TP rebar in flexural
concrete members.
Early pullout testing demonstrated a promising
bond performance of the rotary stamp formed
rebar with respect to ASTM D7957[31]
, which dictates
minimum performance properties for glass fiber
Figure 11. Early methods of field bending resulted in stirrups that exhibited
fiber buckling.
Figure 13. Thermoplastic rebar tension testing (left), and reinforced concrete beam tests (right).
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|
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SAMPE Journal - January/February 2025
Table of Contents for the Digital Edition of SAMPE Journal - January/February 2025
Contents
SAMPE Journal - January/February 2025 - Cover1
SAMPE Journal - January/February 2025 - Cover2
SAMPE Journal - January/February 2025 - Contents
SAMPE Journal - January/February 2025 - 2
SAMPE Journal - January/February 2025 - 3
SAMPE Journal - January/February 2025 - 4
SAMPE Journal - January/February 2025 - 5
SAMPE Journal - January/February 2025 - 6
SAMPE Journal - January/February 2025 - 7
SAMPE Journal - January/February 2025 - 8
SAMPE Journal - January/February 2025 - 9
SAMPE Journal - January/February 2025 - 10
SAMPE Journal - January/February 2025 - 11
SAMPE Journal - January/February 2025 - 12
SAMPE Journal - January/February 2025 - 13
SAMPE Journal - January/February 2025 - 14
SAMPE Journal - January/February 2025 - 15
SAMPE Journal - January/February 2025 - 16
SAMPE Journal - January/February 2025 - 17
SAMPE Journal - January/February 2025 - 18
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SAMPE Journal - January/February 2025 - 25
SAMPE Journal - January/February 2025 - 26
SAMPE Journal - January/February 2025 - 27
SAMPE Journal - January/February 2025 - 28
SAMPE Journal - January/February 2025 - 29
SAMPE Journal - January/February 2025 - 30
SAMPE Journal - January/February 2025 - 31
SAMPE Journal - January/February 2025 - 32
SAMPE Journal - January/February 2025 - 33
SAMPE Journal - January/February 2025 - 34
SAMPE Journal - January/February 2025 - 35
SAMPE Journal - January/February 2025 - 36
SAMPE Journal - January/February 2025 - 37
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SAMPE Journal - January/February 2025 - 72
SAMPE Journal - January/February 2025 - Cover3
SAMPE Journal - January/February 2025 - Cover4
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