page_title: Eastern span replacement of the San Francisco–Oakland Bay Bridge
section_title: SAS main suspension cable
hierarchical_section_title: Eastern span replacement of the San Francisco–Oakland Bay Bridge / Design and construction / SAS main suspension cable
caption_attribution_description: English: San Francisco - Oakland Bay Bridge (eastern span replacement construction). The blue cage contains tracks to guide the traveler around the northwestern deviation saddle.
context_page_description: The eastern span replacement of the San Francisco–Oakland Bay Bridge was a construction project to replace a seismically unsound portion of the Bay Bridge with a new self-anchored suspension bridge and a pair of viaducts. The bridge is in the U.S. state of California and crosses the San Francisco Bay between Yerba Buena Island and Oakland. The span replacement took place between 2002 and 2013, and is the most expensive public works project in California history, with a final price tag of $6.5 billion, a 2,500% cost overrun from the original estimate of $250 million. Originally scheduled to open in 2007, several problems delayed the opening until September 2, 2013. With a width of 258.33 ft, comprising 10 general-purpose lanes, it is the world's widest bridge according to Guinness World Records.
  The Bay Bridge has two major sections: the western suspension spans and their approach structures between San Francisco and Yerba Buena Island and the structures between YBI and the eastern terminus in Oakland. The original eastern section was composed of a double balanced cantilever span, five through-truss spans, and a truss causeway.
context_section_description: The tower saddle includes eyebars for the attachment of temporary cables that supported four walkways, each a simple suspension bridge (called a catwalk) that allowed access to the cable spinning mechanism and the main cable during construction. In several ways similar to a ski lift, additional superior cables carried one or more of these travelers, wheeled devices that shuttled from one end of the span to the other, pulled by drafting cables manipulated by several winches.
  The main span use a single cable, spun using pre-bundled groups of wires from an anchor point at the eastern end of the main span, across an eastern corner horizontal deviation saddle, over a vertical deviation saddle on the eastern end, up and over the corresponding half of the main tower saddle, down to a 90-degree deviation saddle at the western counterweight, across the counterweight, passing over the hydraulic tensioning saddle, around the opposing western deviation saddle, up to the other half of the main tower saddle, over an eastern vertical deviation saddle down to the final eastern corner deviation saddle, to the appropriate anchor point in the eastern strand anchor opposite the beginning.
  As a bundle is laid down, it was initially supported by supports mounted on the catwalk, then both ends were attached and the cable is tensioned at the eastern anchor points. As with a conventional cable suspension span, all of the tensioned bundles were then compressed into a circular shape and protected with a circular wrap of wire. Saddles for suspender cables were added and suspender cables placed and tensioned. The suspender cable tensioning lifted the span from its supporting falsework.
  In mid-June 2011, preparations for the spinning of the main cable began by installing the temporary catwalks on the SAS span. Both western catwalks were installed and by mid-August, all four catwalks were installed in place and an approximation of the completed outline of the bridge could then be seen. All four catwalks, the traveler, its suspension cable and the drafting cables and the winches and specialized tracks at the deviation saddles had to be in place before strand dragging could begin. These catwalks were required for worker's access to the cable strands for bundling and arrangement as the individual wires are placed.
  Work in September 2011 included the installation of the turning tracks for the travelers at the western deviation saddles. These tracks allowed the continuous motion of the traveler across the western end of the main span. By mid-October 2011, the traveler cables were installed. A temporary group of tower stay cables to the west, intended to resist the overturning forces imposed by the bare main cable, were also installed. Subsequently, the eastern deviation saddles were installed, preparing the bridge for cable placement.
caption: October 1, 2011: Tracks within the blue cage will guide the strand hauler around the deviation saddle, to continue across the jacking saddle and around the opposite deviation saddle.
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