Inspection and Maintenance of Bridge Stay Cable Systems (2005) / Chapter Skim
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Pages 8-36
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From page 8... ...
. The locked coil cable and spiral strands are examples of applications of suspension cable technology to stay cables.
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From page 9... ...
locked coil, (b) helical strand, (c)
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From page 10... ...
However, stay cable systems 0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 7-wire steel strand steel wire steel bar or threadbar other no answer MTE Type P er ce nt o f B rid ge s U.S. Canada FIGURE 6 Types and frequency of main tension elements used.
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From page 11... ...
, all of the major stay cable manufacturers in the United States have at least one system that more or less falls within the point anchorage system described in Figure 8. Shop or Field Cable Fabrications There are two different approaches regarding the assembly and erection of stay cables.
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From page 12... ...
. An FHWA Technical Advisory released in 1994 ("Cable Stays .
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. According to the latest edition of the PTI Recommendations for Stay Cable Design, Testing and Installation (2001)
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From page 14... ...
The Storchenbrücke (Stork) Bridge in Winterthur, Switzerland, incorporates two CFRP stay cables, each consisting of 241 parallel pultruded CFRP rods of 5 to 6 mm in diameter (Hooks et al.
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From page 15... ...
However, none of the Canadian bridges included galvanized MTE in contact with cement grout. It was also believed that the process of galvanizing would degrade the tensile strength of strand and its fatigue life ("Cable Stays .
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The Buy America Act enacted by the U.S. Congress in 1933 has so far effectively prevented the importation of stay cable-quality galvanized strands.
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From page 17... ...
These systems have been common in all recently constructed cable-stayed bridges in the United States. Examples of bridges using these types of strands are the Cape Girardeau Bridge in Missouri and the Sixth Street Viaduct Bridges in Wisconsin.
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From page 18... ...
Georges, Delaware, cracking of the steel sheathing was noted on one of the stay cables. This cracking was attributed to the position of a grout vent hole at a high-stress location near a pylon.
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From page 19... ...
Portland Cement Grout There have been a variety of opinions on the merits of cement grouts for stay cables. As stated earlier, the practice of grouting stay cables comes from the post-tensioning technology, and not from the suspension cable technology.
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From page 20... ...
, and the Fred Hartman Bridge (Texas) , the HDPE sheathing was partially removed (windows cut)
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From page 21... ...
That is the approach used on the Charles River Crossing Bridge in Boston, Maumee River Bridge in Ohio, Sixth Street Viaduct Bridges in Wisconsin, and Cooper River Bridge in South Carolina, where individually coated and sheathed strands (or epoxy-coated strands) are used inside HDPE pipe without cement grout.
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From page 22... ...
cases referred to neoprene boots that are not as described above. STAY CABLE DESIGN CHALLENGES Aside from structural strength, the design of stay cables also must address the challenges of corrosion, fatigue, vibration, inspectability, and maintainability.
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From page 23... ...
As will be seen later in this report, recent trends have been toward inclusion of additional features such as vibration control and force measurements as part of the cable design. This constitutes a "system approach" to the design of stay cables.
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From page 24... ...
The authors attributed failures to many factors including misalignment of cables, missing protection at the sockets, cable vibrations, and possible effects of deicing salts. The Lake Maracaibo Bridge in Venezuela also suffered corrosion of its galvanized locked coil cables after fewer than 18 years of service, and all of its cables were subsequently replaced in 1980 ("Cable Stays .
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From page 25... ...
. These bridges were built in the early FIGURE 33 Neoprene washers on the Luling Bridge at the exit point of cables from the steel box (Telang et al.
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The cable had failed in an area near the entrance to the bottom anchorage. Subsequent ultrasonic testing on other anchorages revealed damage to other cables, with up to 62% wire breaks.
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From page 27... ...
As will be discussed later, assessments of MTE corrosion in cablestayed bridges are, in many cases, very difficult. Fatigue The PTI Recommendations for Stay Cable Design, Testing, and Installation (2001)
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From page 28... ...
vibration phenomenon in stay cables. It was first reported on the Meiko– West Bridge in Japan in 1986 (Matsumoto 2000)
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From page 29... ...
also reported on the instrumentation and long-term vibration monitoring of the Fred Hartman and Veterans Memorial Bridges in Texas. Figure 42a shows a sample histogram of dominant modes for one stay cable, and Figure 42b shows vibration amplitudes versus wind speed for the same cable.
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From page 30... ...
In -p la ne a cc el er at io n – 5m in u te R M S (g ) mode 2 mode 3 mode 4 mode 5 mode 7 FIGURE 42 Vibration data from Fred Hartman Bridge: (a)
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From page 31... ...
These bridges are the Cochrane Bridge in Alabama; Talmadge Memorial over the Savannah River in Georgia; Clark in Alton, Illinois; Burlington in Iowa; Veterans Memorial between Bridge City and Port Arthur in Texas; and Fred Hartman in Houston, Texas. In Canada, the Prince's Island and Fox Hollow bridges (Alberta, Calgary)
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From page 32... ...
to control vibrations. In the Cooper River Bridge in South Carolina, viscous dampers will be installed, but provisions for future installation of cross cables are made in case they are needed.
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From page 33... ...
0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 yes - from the beginning yes - retrofitted to correct vibrations no no answer Cross Cables Pe rc en t o f B rid ge s U.S. Canada FIGURE 46 Percentage of bridges using cross cables.
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From page 34... ...
Question 5 in the survey asked whether the current inspection, testing, monitoring, and repair methods were effective 34 and adequate. Figure 49 summarizes these responses.
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From page 35... ...
As will be discussed later, there is a wide variation in topics discussed in individual maintenance manuals. Survey question 10 asked whether an up-to-date resource such as a national database of information on stay cable inspection, repairs, and testing would be a useful tool.
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From page 36... ...
. FABRICATION AND ERECTION OF STAY CABLES As discussed in the previous section, stay cables can be either shop- or field-fabricated.
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