CHAPTER 3: FRP W-BEAM GUARDRAIL
Guardrails are common and are critically
important elements of highway safety systems.
Every year about 2,165 km (1,345 mi) of guardrails
are constructed on Federal projects (McDevitt and
Dutta 1993). The existing W-beam design shown
in Figure 6 is specified under the "Standard Speci-
fication for Corrugated Sheet Steel Beams for
Highway Guard Rail, AASHTO Designation:
M180-84." The beam consists of open hearth sheet
steel with the following mechanical properties:
Yield point,
minimum: 344.5 MPa (50,000 psi)
Tensile strength,
Figure 7. Three-point bending test of standard AASHTO
minimum: 482.3 MPa (70,000 psi)
W-beam--Class A.
Elongation,
minimum: 12%
Tests are done per the ASTM A525 procedure.
Figures 8a and b for MW-1 and MW-2, respec-
Depending on the type of beam, the thickness var-
tively. The loading and the two support points
ies from 2.67 mm (0.105 in.) to 2.82 mm (0.111 in.)
were provided by 50.8-mm- (2-in.-) diam. hard-
for Class A beams, and 3.43 mm (0.135 in.) to 3.58
ened steel rods. Loading was applied by a screw-
mm (0.141 in.) for Class B beams.
driven testing machine. The midpoint deflection
and the load were measured manually. The beams
started yielding at about 60.08 kN (13,500 lbf)
Initial tests
Under the current investigation, the W-beam
load. The yielding happened primarily at the
material considered was the fiber-reinforced plas-
loading contact point of the beam to the rod, as
tic (FRP) composite. Initial tests were the three-
shown in Figure 9.
point flexural bending tests on two 1.22-m (4-ft)
To understand the comparative behavior of an
long pieces, MW-1 and MW-2, of AASHTO Class
FRP beam under similar tests, we tested a com-
A W-beam design, with a loading span of
mercially available FRP W-beam (manufactured
609.6 mm (24 in.) (Fig. 7). The load-deflection and
for some special applications) with a thickness
energy absorption characteristics are shown in
of 3.81 mm (0.15 in.) (Fig. 10). As for the steel
Load
Load
Energy
Energy
Deflection (in.)
Deflection (in.)
a. MW-1.
b. MW-2.
Figure 8. Load deflection characteristic of AASHTO W-beam under three-point flexure test.
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