Ted Hall of Hatch Mott MacDonald, Program Manager for the Bay Area Toll Authority, talked about the newly opened $6.4 billion San Francisco-Oakland Span of the Bay Bridge. The signature span, which opened on Labor Day weekend, is the longest self-anchored suspension bridge in the world.
The new span replaces the old cantilever bridge built in 1936 whose upper deck collapsed during the Loma Prieta earthquake in 1989. The span uses a single cable which begins and ends at Yerba Buena Island. Because the span is asymmetrical, the shorter section of the span terminating at Yerba Buena Island is weighed down by massive concrete weights which counteract the forces of the longer section of the span terminating in Oakland.
The central tower is comprised of four separate columns joined by replaceable box structures designed to absorb seismic shifting. In the event of a severe earthquake, the box structures absorb the seismic energy rather than the columns and can be replaced if damaged, and the columns themselves are not directly connected to the roadway so as to prevent damage to the roadway and commuters in the event of an earthquake.
In addition to the engineering aspects of the bridge, Ted talked about the financing for the new span (it was paid for primarily through toll fees), how politics and public opinion played a part in the design of the span (the span went through several significant design changes from a simple retrofit to an elevated viaduct to the current signature span), and, of course, the now infamous bolts (the bolts are being replaced but the new span is safer than the old span).
Ted also brought in a scale model of the span which he built entirely out of Legos (now we know what engineers do on their downtime) and showed a time-lapse video of the construction of the span (which he said, not only kept the public apprised, but turned out to be very useful during construction) like the one below showing 42,000 hours of construction in four minutes.
Thank you Ted for speaking, and thank you to the many attendees for attending!