SAS main suspension cable Eastern span replacement of the San Francisco–Oakland Bay Bridge

compaction test section of sas cable; distinct colors mark individual parallel wire strands, each bundle of 127 pencil-thin wires. there 137 such bundles, each individually terminated @ eastern end of sas.

the tower saddle includes eyebars attachment of temporary cables supported 4 walkways, each simple suspension bridge (called catwalk) allowed access cable spinning mechanism , main cable during construction. in several ways similar ski lift, additional superior cables carried 1 or more of these travelers, wheeled devices shuttled 1 end of span other, pulled drafting cables manipulated several winches.

cable images


















































































































































june 24, 2011: gantry crane has been removed , 2 of 4 temporary catwalks have been installed.

the main span use single cable, spun using pre-bundled groups of wires anchor point @ eastern end of main span, across eastern corner horizontal deviation saddle, on vertical deviation saddle on eastern end, , on corresponding half of main tower saddle, down 90-degree deviation saddle @ western counterweight, across counterweight, passing on hydraulic tensioning saddle, around opposing western deviation saddle, other half of main tower saddle, on eastern vertical deviation saddle down final eastern corner deviation saddle, appropriate anchor point in eastern strand anchor opposite beginning.

as bundle laid down, supported supports mounted on catwalk, both ends attached , cable tensioned @ eastern anchor points. conventional cable suspension span, of tensioned bundles compressed circular shape , protected circular wrap of wire. saddles suspender cables added , suspender cables placed , tensioned. suspender cable tensioning lifted span supporting falsework.

october 1, 2011: tracks within blue cage guide strand hauler around deviation saddle, continue across jacking saddle , around opposite deviation saddle.

in mid-june 2011, preparations spinning of main cable began installing temporary catwalks on sas span. both western catwalks installed , mid-august, 4 catwalks installed in place , approximation of completed outline of bridge seen. 4 catwalks, traveler, suspension cable , drafting cables , winches , specialized tracks @ deviation saddles had in place before strand dragging begin. these catwalks required worker s access cable strands bundling , arrangement individual wires placed.

work in september 2011 included installation of turning tracks travelers @ western deviation saddles. these tracks allowed continuous motion of traveler across western end of main span. mid-october 2011, traveler cables installed. temporary group of tower stay cables west, intended resist overturning forces imposed bare main cable, installed. subsequently, eastern deviation saddles installed, preparing bridge cable placement.

cable placement

the cable construction technique differed used earlier western spans , similar conventional suspension bridges. in method, cables spun few wires @ time, bundles made wires spun pulling loop along cable s route. sas used different technique, wire strands pre-fabricated mile-long cable bundles bundle terminations in place, pulled dragging 1 end through route. after attachment termination, tensioning operation performed on each bundle @ eastern anchor point, , bundles suspended few feet above catwalk. total of 137 such bundles installed. bundles positioned, temporarily tied form cable. cable in place in late may 2012. later compacted circular shape, , wrapped protective wire jacket. in mid-march 2013, western portion completed , catwalks removed. wire wrapping still in progress on eastern portion.

since main cables curve , suspender cables splay outward deck edge, saddle design individual location, being fabricated in mirror image pairs each side. in mid-june 2012, saddles in place upon main cable. wire rope suspender cables draped on these saddles , later pulled outward , attached projections main deck.

on conventional suspension bridge, sections of deck hung in place , tension suspenders. proper initial length of each suspender predetermined engineering calculations , adjustments required segment relative positioning , equality of load distribution amongst several suspenders of section. on bridge, deck sections in fixed relative position (being joined , resting upon falsework) , suspender cables must brought specific tensions individually in order tension main cable. jacking saddle on western end used balance tension among sections of single main cable.

suspender cable tensioning performed in stages. degree of tensioning @ various stages , order of tensioning critical procedure.

starting in 2011, proper balance between main cable runs , suspender cables , proper tension applied main , suspender cables. on november 20, 2012, process completed made sas portion of bridge self-supporting. after that, falsework removed.