Tuesday, February 10, 2009

Arch Bridges: The Lilac Road Bridge

As I've previously mentioned, California too often adopts a cookie-cutter approach to bridge design. All the more remarkable then when a truly unique and dramatic bridge gets built.

The Lilac Road Bridge is a reinforced concrete arch built high over I-15, a little north of San Diego, California. It was designed by Caltrans architect William Wells (with help from Caltrans engineers) and it was completed in 1978.

The question of the architect's role in bridge design is an interesting one. David Billington in 'The Tower and the Bridge' writes that an aesthetic experience occurs when we can see clearly how a structure resists the forces acting on it. This seems hardly the role for an architect, who is more concerned with visual themes and variations in a design. Still, it is often a collaboration of engineer and architect that creates the finest bridges.

A few days ago, this blog presented a photo of the Millenium Bridge, a collaboration between the engineer Ove Arup and the architect Norman Foster.

The Lilac Road Bridge is a very dramatic and attractive bridge. It looks like a giant scythe poised over the roadway. The way the arch joins the deck looks organic, more like the way a plant grows than something made by humans. I think that this bridge is as good as anything done by Eiffel, Maillart, Menn and the other great designers of arch bridges.
Creative Commons License
Arch Bridges: The Lilac Road Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution 3.0 United States License.

3 comments:

Anonymous said...

It's a stunning bridge. I've long wondered how it got there, and what traffic could justify its expense... and been very grateful it is there because its beauty justifies its existence.

Just today learned the name and the date of the bridge.

I had guessed that it went back to the early sixties... and now I would guess that the designer did most of his work then, even though this bridge was built in '78.

I used to drive under it twice weekly for about a year, maybe ten years ago. What really fascinated me was the continuous tapering of the dimensions of the arch, in reflection of the point-by-point continuously changing stress requirements. It tapers down as the arch goes off shear toward compression. Lovely.

So you have a continuous and symmetrical treatment of stress requirements offsetting the asymmetries of road slope, and landing points for the arch.

One conveyance showing purpose; one support structure showing the forces. Continuous, organic, beautiful.

Anonymous said...

This bridge was designed by my Dad, Fred G Michaels, who has since relocated to Black River Falls, WI. The facts in this article are disappointing to say the least. He has another bridge to his credit, Old Miramar north of 805 and I5 in CA. He actually won an award for this design....although it escapes me what it was....I can answer that one with a simple phone call.

Anonymous said...

http://members.cox.net/mkpl2/hist/77_15lilac.jpg