The Bay Bridge’s self-anchored suspension span, the world’s largest structure of its kind, will be officially completed on Friday.

Construction crews will place the 28th and final piece of the self-anchored suspension (SAS), which connects the Yerba Buena Island portion of the Bay Bridge to its eastern skyway.

Unlike regular suspension bridges, which are anchored into the ground, the SAS has a single cable that weaves down and through the undercarriage of the span, reinforcing support through its own tension (much like the design of an arm sling.)

On Friday, officials throughout the Bay Area will converge at the site to celebrate the placement of the final piece of the SAS structure. San Francisco Mayor Ed Lee and Oakland Mayor Jean Quan will both attend the event, which will take place at 10 a.m.

wreisman@sfexaminer.com