As a resident of the Bay Area, I will never forget October 17, 1989. The memories from that day are still clear. The Loma Prieta earthquake, also known as the Quake of '89 and the World Series Earthquake struck the San Francisco Bay Area at 5:04 pm PDT. Caused by a slip along the San Andreas Fault, the quake lasted 10–15 seconds and measured 6.9 on the magnitude scale. The earthquake wreaked havoc; buildings in the Marina district of San Francisco and the Santa Cruz area collapsed, the Cypress Structure at the 880 interstate highway in West Oakland and a part of the Bay Bridge collapsed.
The new eastern span of the San Francisco-Oakland Bay Bridge was completed earlier this month and the new bridge was ready crossing on Labor Day.
From Design to Construction: 1913 to 2013
An initial sketch of the Bay Bridge from 1913.
Here is the Bay Bridge today (2013).
Why was construction needed?
The Loma Prieta earthquake left the bridge damaged. A 76-by-50-foot section of the upper deck on the eastern cantilever side fell onto the deck below. The quake caused the Oakland side of the bridge to shift 7 inches to the east, and caused the bolts of one section to shear off, sending the 250-short-ton section of roadbed crashing down like a house of cards. Immediately after Loma Prieta, the bridge was closed for a month as construction crews made repairs. A bigger issue bubbled to the surface, if another earthquake were to happen—would the bridge hold up? The seismic retrofitting project started.
Did you know that the Bay Bridge is actually two bridges and a tunnel? The Eastern Span from Oakland to Yerba Buena Island was replaced with a new self-anchored, single tower suspension bridge and the east span highway. The Western Span from Yerba Buena Island to San Francisco has been retrofitted and upgraded to meet the most current seismic standards. The work included adding massive amounts of steel and concrete to strengthen the entire Western Span allowing for a wider range of movement during an earthquake. Crews installed new, state-of-the art devices to isolate, absorb or diffuse the impact of an earthquake.
The new bridge is the world's longest self-anchoring suspension bridge. This design includes innovative "shear link" beams and "hinge-pipe" beams which act as shock absorbers, and will enable the bridge to withstand the largest plausible earthquake for the next 1,500 years.
Much of the work came down to simple "nuts and bolts" retrofitting. The bridge's twin suspension spans were strengthened by adding new steel plates and replacing half a million original rivets with almost twice the number of high-strength bolts. In total, 17 million pounds of structural steel were added! New bracing was added under both decks, and all of the "laced" diagonal crossbeams connecting the upper and lower road decks were replaced with perforated steel. Piers were encased in heavy concrete jackets and additional anchor bolts were installed to fasten tower legs to pedestals.
Bay Bridge suspension cables are composed of 17,000 individual steel strands. Each strand can dangle one Hummer!
Before being built, the bridge was modeled, simulated and analyzed in 3D and the phasing of the construction was modeled in the fourth dimension (time).
The Results
The project cost approximately $6.4 billion and by spanning to 2.2 miles, the new Eastern Span is making California history. Over 280,000 cars cross the Bay Bridge every day. Motorists have a new driving experience, as traffic moves from the upper and lower decks of the original bridge to the parallel, side-by-side decks of the new east span. The new side-by-side configuration opens up panoramic views of the bay and the East Bay hills. From driving beneath a canopy of white suspender ropes to the wider road-decks with shoulders on either side, a drive across the new east span is nothing like it used to be. The views are breathtaking! Caltrans is “encouraging motorists to drive safely and keep their eyes on the road, and let their passengers enjoy the much more picturesque ride.”
As a citizen of San Francisco and an employee of Autodesk, I’m especially proud of the Bay Bridge. I enjoy telling my nieces and nephews about the bridge renovation and how Autodesk software played a part in this historical project.
To learn about the Bay Bridge, visit the Autodesk Gallery page and if you are in the neighborhood, stop by and see the hands-on exhibit.
Lastly, here is my favorite video. Watch 42,000 hours on construction work in 4 mins!
~Sunny
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