Sunday, February 25, 2007

Arched Bridges

It seems that arched suspension bridges over freeways are the latest thing. These bridges have large arches on each side of the bridge, anchored at the ends, and cables to suspend the surface of the span over the freeway. Here are some examples.

I took this first photo last October on northbound US 59, the Southwest Freeway in the museum district of Houston, not far from the downtown split. Even though the highway is northbound, it actually runs east and west here, so you are looking east. These bridges replaced older, standard bridges that used to cross the freeway at Hazard, Woodhead, Dunlavy, and Mandell. The old Hazard Street bridge was appropriately, though inadvertently named, since that bridge didn't have quite enough clearance for some 18-wheelers, and there were frequent trucks hitting the bridge and getting stuck under it. Part of the problem was that the freeway goes into a trench at Hazard, so the pavement was descending about where the bridge was.

This part of the Southwest Freeway is also a Texas rarity, as it is like freeways in most other places, in that it is lacking what Houstonians call "feeder streets", also known as frontage roads or service roads. The trench keeps the noise down for the residential community on the sides of the highway.

This stretch of the freeway was reconstructed in 2000-2001. For another view, CLICK HERE to see it on the web site.

Here is another example of a suspended arch overpass. This is in the Denver area. The big difference here is that despite the similarity to the design in Houston, these are pedestrian bridges rather than vehicular ones. They were recently completed as part of the TRex, or Transportation Expansion project that widened I-25 on the south side of the Denver metropolitan area, and added a light rail line. There is a series of these bridges south of I-225 to permit people to get across the freeway to the trains which run on the west side of the freeway; on the right side of this photo. The photo above is at the Belleview Station.

There is one of these bridges that is different than the others. That is the one near Park Meadows Mall. It is a double arch, and is in the photo below.

Given the similarity of the designs of the Denver and Houston bridges, it would be interesting to know if they had the same engineer, or if this is just a common design that is well known. Either way, I don't recall seeing this type of bridge over freeways anywhere else but in these two places.

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