复合材料高强度混凝土桥梁英文文献和中文翻译(3)
reinforcement, but featured dierent concrete formula-
tions and dierent tendon pretension levels. Beam 1
suered from a design calculation error and failure of
some prestressing tendons, but was salvaged as a useful
test specimen. Fiberglass rebar was used for shear
reinforcement in Beam 1, and was also used in a shear-
critical region of Beam 2, the remainder of which
featured steel shear reinforcement. This section docu-
ments the material properties, beam design, beam
fabrication, and beam testing. A discussion of the test
results is included.
3.1. Materials
The composite prestressing material was Leadline
cable, manufactured by the Mitsubishi Kasei of Japan.Leadline cable features unidirectional carbon ®bers in
an epoxy matrix. Surface deformations are milled into
the surface in a helical pattern. Manufacturer-supplied
properties and characteristics of Leadline are shown
in Table 1. The epoxy matrix has a glass transition
temperature, Tg, of 120°C (248°F).
Marshall Industries of Lima, Ohio, manufactured the
composite rebar shear stirrups used in the program. The
composite rebar, named C-Barä, is fabricated using a
continuous hybrid pultrusion/compression molding
process. C-Bar consists of an inner core of unidirectional
E-Glass ®bers embedded in a PET matrix, and an outer
layer composed of sheet molding compound with
chopped ®ber mats embedded in urethane-modi®ed
vinyl ester. Uniform deformations on the surface inhibit
longitudinal movement of the bar. According to the
manufacturer, tests have shown that C-Bar resists de-
Manufacturer-supplied properties of Leadline CFRP cable
Characteristic Leadline GA-D10
Matrix material Epoxy
Carbon ®ber volume
fraction
65%
Cable diameter 10 mm 0.394 in
Nominal cross-section area 71.8 mm3
0.1113 in2
Intact cross-section area
(measured)
69.5 mm2
0.1075 in2
Ultimate tensile load 186 kN 41 000 lb
Ultimate tensile stress 2600 MPa 377 ksi
Longitudinal thermal
expansion
0.68 ´ 10ÿ6
/°C 0.38 ´ 10ÿ6
/°F
Longitudinal Young's
modulus
147 GPa 21.4 Msi
Extension at break 1.60%
Matrix material 1.6gradation when exposed to deicing salts, seawater, and
wastewater. Table 2 provides the mechanical properties
of C-Bar, obtained from product literature. C-Bar can
be fabricated with curves having a 51 mm inside radius,
where all curves must be in the same direction (no
reversed curves or S-shapes). #4 bar steel (414 MPa
yield strength) shear stirrups were also used in the pro-
gram, as described in Section 3.3.
Two dierent high-strength concrete formulations
were used to fabricate the two beams. Twenty-eight day
compressive strength cylinder tests showed a compres-
sive strength of 86.3 MPa for the ®rst beam and
71.1 MPa for the second beam. Mix designs, formulated
by Anderson Concrete of Columbus, Ohio, are provided
in Table 3.
3.2. Design and ultimate strength analysis
This section documents the procedures used to obtain
the prestressing and shear reinforcement speci®cations
for the nominal test beam design, and to predict the
ultimate strength capacity of the as-built beams. Two
beams were built during the program. Using the nomi-
nal material properties for Leadline cable and assuming
69.0 MPa compressive strength for the concrete, the
prestressing for ®rst beam (Beam 1) was designed.
During fabrication of Beam 1, breakage of several
prestressing tendons occurred, as described in Section
3.3. The second beam (Beam 2) was then fabricated
using a lower target pretension value for the tendons.
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