Saturday, January 30, 2010

Peru's Bridges: Puente Locumba

We've looked at bridges across several of the major rivers in Peru. Moving to the south we've crossed the Rio Camana, Rio Sihaus, Rio Chili, Rio Tambo, Rio Moquegua, Rio Locumba, and Rio Sama.

All these rivers flow out of the Andes and across parched desert on their way to the Pacific. When I was there in 2001, there was talk of damming these rivers and turning the desert into a breadbasket like in California. Hopefully, they won't be stealing water from the campesinos in the process. When this was done in California, the poor farmers in the Owens valley tried to stop them without success. At least according to the movie Chinatown.

I'm skipping several bridges on Tambo and Moquegua in order to look at a bridge on the Rio Locumba. Puente Locumba is a two-span continuous, haunched T girder reinforced concrete bridge on a pier wall and seat-type abutments. The deck is about 100 feet long by 30 feet wide and is supported on four girders.  Gabions are strung along the sides of the river for erosion control.

During the earthquake, the superstructure moved back and forth, damaging the abutments and the soil behind the abutments dropping the approaches several feet There were several optical cables on the bridge that were also damaged.

When we were at the bridge site about a month after the earthquake, a drilling rig was sitting on the north embankment suggesting that soil testing was being completed before repairs were made. Note the temporary bridge behind Puente Locumba consisted of gravel poured into the river as a driving surface with a culvert at the center to allow the water to flow.

I find this two span continuous bridge to be a very attractive solution when a river is too long to be spanned by a single span. The bridge is like a children's teeter-totter, balanced securely between the two abutments. I also like the green superstructure and striped barrier rail. To me this is a quintessential Peruvian bridge, elegant, simple, and attractive.

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