Inspection and Maintenance of Bridge Stay Cable Systems (2005) / Chapter Skim
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Pages 50-58
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From page 50... ...
The following is a list of the items found in the different manuals that are related to stay cables: • Bridge description; • Design considerations; • Loads; • Stay cable details: identification numbers, number of strands and wires, diameter of cable, mass per unit length, inclination angles, length, estimated cable tension at the end of construction and after creep and shrinkage effects are taken into account; • Stay cable shop drawings including as-built anchorage design, materials used, any repairs done during construction, and history of problems during construction; • Inspection and maintenance frequencies, and qualifications of inspection teams; • Information on access: platforms, ladders, and snooper trucks; • Cable retensioning procedures; • Cable replacement procedures including traffic patterns and specific replacement procedures; • Inspection procedures for anchorages, guide pipes, neoprene boots, neoprene washers, sheathing, cross cables, dampers, and so forth, including identification of critical areas and how and where to look for moisture and corrosion; • Listing of designers, contractors, and suppliers of stay cables and components; • Summary of qualification test results for MTEs; • Summary of qualification test results for the entire stay cable system; • Deck elevation surveys; • Repair procedures including sheathing repair, PVF tape repair, repair of damage to guide pipes, and welded connections; • Safety and traffic control during inspections; • Description of methods for measuring cable forces; • Inspection forms; and • Deck elevation survey forms. The examination of the maintenance manuals did not identify cases where any of the following methods discussed in the literature were included in the manuals: • Recommendations for baseline measurements of cable frequency, damping ratio, cable sag, and cable inclination angles (at specific points accessible by inspectors)
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From page 51... ...
MITIGATION OF STAY CABLE VIBRATIONS A wide variety of solutions to the problem of stay cable vibrations have been proposed and/or implemented. These mitigation approaches can be categorized as modifications to the surface of HDPE pipe, cross cables, viscous dampers, viscoelastic dampers, friction dampers, tuned mass dampers, semiactive and active dampers, and others.
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From page 52... ...
Cross Cables Cross cables, secondary cables, cable restrainers, or cross ties are used to connect different stay cables within a cable plane. Figure 70 shows a cross cable installed on SR-46 over the East Fork White River in Indiana.
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From page 53... ...
. Bournand reported that the cross cables on the Fred Hartman Bridge in Texas failed one year after installation as a result of fatigue and fretting.
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From page 54... ...
In this discussion, they are all referred to as viscous damper as long as they meet the definition given. Viscous dampers for stay cables have been installed on a large number of cable-stayed bridges worldwide, including the Sunshine Skyway Bridge, Cochrane Bridge, and Erasmus Bridge.
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From page 55... ...
to develop an equation for calculating the first mode damping contribution by a viscous damper. This study indicated that the influence of cable sag was insignificant for the range of parameters found in stay cables.
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From page 56... ...
The authors reported that the potential for using semi-active dampers to control stay cable vibrations "has been demonstrated" in comparison with passive viscous dampers. FIGURE 75 Viscoelastic and hydraulic dampers (Stubler et al.
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From page 57... ...
reported on damping tests on a scale model of a stay cable. They tested a number of approaches for cable damping including using common neoprene rings, latex grout as filler inside HDPE, a liquid damper, application of spiral adhesive damping tapes around HDPE, and filling of the guide pipes with a low stiffness polyurethane.
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From page 58... ...
There are a number of other patented concepts for damping stay cable vibrations including flexible damper bands by Sarkar et al.
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