Soaring Design Makes New Bay Bridge Span An Artistic Triumph
SAN FRANCISCO (CBS) – It rises some 525 feet above the bay, blazing white against the sky. The centerpiece of a creation blending architecture and engineering in a way never done before.
According to architect Donald McDonald, “There’s chaos and there’s order, and when you bring the two together you get electricity. How are you going to make them work? That’s when, for me, ideas start to really pop.”
MacDonald is the man who came up with the idea: a single tower, self-anchoring suspension bridge on a scale never tried before.
When asked by KPIX why the bridge is so different looking, MacDonald replied, “Well the thing about the bridge making it quite different structurally is the self anchoring suspension bridge. It’s a difficult bridge to build because you have to build another bridge to carry the deck. Once that deck can be carried on its own, then you take away the initial bridge.”
Everyone is familiar with the Golden Gate Bridge. Its separate twin cables are suspended over twin towers, and then anchored to the ground in concrete and rock. MacDonald said his design is radically different because it uses a single continuous cable anchored to the deck.
“It was a way you do a suspension bridge without anchoring the cables into the ground,” MacDonald said.
Here’s how it works: engineers build the deck on temporary supports; then the tower goes up, looping up and over the tower are strands of steel cable the thickness of a pencil. Those strands wrap around and back over the tower before being anchored to the deck. Workers then bundle the strands together to form the 10 million pound main cable holding up the parallel roadways, which hang alongside the huge tower without actually touching it.
MacDonald said he came up with his vision by looking at America’s space program in the late 1960’s, and patterned his design after the Saturn 5 rockets that took the astronauts to the moon.
“I had to get something out there I felt would be lasting for the next 50 years. I felt, well, there will be a lot of space exploration. There will be rockets here and there, so it has a lot of similarities. The base of it is like the base of our tower. The vertical elements, the negative spaces are like ours, the top has these rounded elements like ours. So when I matched them up it was just dynamite how they came together.”
Bringing elements together is a hallmark of MacDonald’s design. His almost compulsive need to match things up can be seen throughout the bridge – if you know where to look.
“If you look at the piers under the main decks, the viaducts, you’ll see all the corners are the same shape as the legs of the tower. The same shape as in the light standards that are held up. So this pattern is repeated everywhere we can enforce it,” McDonald said.
No detail went overlooked; from the color white to match the huge container cranes in the Port of Oakland, to the geometric slope of the single cable to match the iconic great Golden Gate.
MacDonald said he wants the average commuter to understand the artistry of the bridge.
“That bridge is something we want everybody to have a piece of, but also my theory was we could take it to another level the average man wouldn’t get to, and that’s why we think we’re good bridge architects.”