Today’s Memorial Bridge runs along the East Coast of the U.S. across the Piscataqua River. It replaced the original bridge of 1923. It is equipped with a vertical lift that raises the bridge to let ships sail under it. The bridge must rise more than 128 ft at an average rate of about 4ft/sec.
As they are custom-built, these cables also tend to have extensive lead times, which can back up project deadlines and run costs up further. Right after installation, droop cable requires extensive testing; many bridge proposals outline the full test procedure as a part of the initial agreement, including who must be present as a test witness. Then, once in service, the repeated lifting motion lead to frequent breaks and damage to the cables.
Motor cables, heavy-duty CF3000 CF9, were enclosed in thermoplastic elastomers (TPSs) and resisted hydrolysis, microbes, UV, oil, and fire. The metal-free cables for fiber optics, CFLG, are protected by a polyurethane other jacket, remain flexible in temperatures down to −40 F°, and resist UV and oil.
The lifting bridge uses pre-assembled igus’ readychain cables and cable carriers instead of the original hanging cables. (The orange lines show where one of the flexible cable carrier is mounted behind a major support beam.) They offer a much higher level of safety and reliability combined with reduced maintenance.
The igus team worked directly and closely with the bridge’s design and maintenance teams, creating a custom metal trough to house the cable carrier system, blending igus design principles with the bridge itself. A combination of structural steel plates, some more than 10 mm thick, were used to create the trough, which was designed to accommodate wind loading, sea, salt, and UV exposure, as well as bridge design safety standards and customer requests.
The new cable management systems can be seen in operation in the video clip below.
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