When completed, the eastern span of the new Bay Bridge, will include the longest self-anchored suspension bridge in the world. Self-anchored sets itself apart from typical bridges that anchor their cables from the bridge to the land. In the case of the Bay Bridge, the supporting cable will be cemented into the roadway, hoisted over a massive center column, and cemented in the roadway on the other side.
So it's no wonder that it is featured as one of our exhibits in the Autodesk Gallery at One Market.
Here's a cross-section of the supporting cable - actually 17,349 individual steel strands. The strand ends have been colored as part of a compression test. The goal for the strands is to stay clustered to maintain structural integrity. The coloring helps identify stands that go astray.
In 2010, as part of my gallery ambassador training, I took a tour by boat to check out the bridge early in its construction:
On Wednesday I had the pleasure of being part of a walking tour of the bridge. Lead once again by the always informative and entertaining, Bart Ney, our group got to go beneath the roadway to marvel at the engineering that makes the new bridge so earthquake tolerant. Though the bridge has many seismic features, something that stood out to me was:
- The bridge is made up of steel-reinforced concrete sections.
- Each section stands alone.
- The sections are connected by steel portions that act like an accordion.
- In the event of an earthquake, the accordion portions expand and contract to absorb the effects of the earthquake.
The goal of the bridge redesign is to allow emergency vehicles to be able to use the bridge immediately after an earthquake and to be able to repair it without having to rebuild any sections. We got to see these accordion structures from below the roadway:
and from above:
Another interesting aspect is the pedestrian access. The pedestrian portion extends from the side of the bridge and is one foot higher than the roadway. This will give pedestrians a more pleasant experience.
The new Bay Bridge is being built to withstand 1,500 years of seismic activity. Although not needed yet (since the concrete and steel are plenty strong enough now), the bridge includes cement footings with holes for additional cables. In 150 years when the bridge needs a tune-up, steel cables can be passed through these holes and tightened to shore up the bridge and reduce its sag.
In other words, the engineering infrastructure for a facelift is being put in now. Now that's thinking ahead.
Marveling at engineering is alive in the field.