As progress on the Bureau of Engineering’s Sixth Street Viaduct Replacement Project moves closer to completion, the exciting process of installing hanger cables comes into focus. Providing both function and style, each of the 20 arches (10 sets of two) will be embedded with crisscrossing cables connecting to edge girders located at the bridge deck level. The edge girders have cable embeds spaced 9 feet apart. As the arches curve, their embeds are spaced apart at various distances.

Once complete, the cables will provide structural support for the deck, allowing the temporary falsework that has been holding up the bridge will be removed. This will enable the viaduct to be completely freestanding.

The viaduct will have a total of more than 15,000 feet of tensioned cables and they have to be installed so they can be adjusted one final time after the bridge settles into place during construction.

Each cable has a custom-designed strain gauge which allows engineers to stress the cables after installation and monitor the loads as the rest of the bridge hanger cables are tensioned. Bridge engineers used a testing warehouse to finalize the design of the strain gauge to handle the unique installation of the hanger cables. The cable strands were first tested at a load of 100,000 pounds to calibrate, then the final cables were cycled through loads of over 585,000 pounds to ensure the length of the cables would remain constant in supporting the final bridge load.

Keep an eye on the bridge as the hanger cable installations bring us closer to the final vision of the Sixth Street Viaduct.

The City of Los Angeles Bureau of Engineering is leading the construction of the new, $588 million Sixth Street Viaduct Replacement Project, the largest bridge project in the history of Los Angeles. The completed structure will be a 3,500-foot long viaduct connecting Boyle Heights and the Arts District across the Los Angeles River. The original viaduct was built in 1932, but had significantly deteriorated due to "concrete cancer"; it was demolished in 2016. The new viaduct will have ten pairs of lit arches, bike lanes and wider sidewalks. When the viaduct is completed, work will begin on the Sixth Street PARC, 12 acres of recreational and open space under the bridge. The bridge is funded primarily through the Federal Highway Administration, with additional City support. The viaduct will be completed in Summer 2022.

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