Thursday, January 28, 2010

Peru's Bridges: Puente Freyne (2)

A view in the opposite direction (toward the northwest) at Puente Freyne and the Tambo River. We are about six miles from the Pacific Ocean. You can see in Google Earth (below) that the river bends back and forth around sandbars  between straight, artificial banks, probably for flood control.

The roadway runs along the coast and then goes inland for several miles before crossing the river and turning back to the coast. Perhaps this is to provide transportation to the farms along the river. In Google Earth (below) you can see a weir just downstream of the bridge and irrigation canals to water the crops in the valley. Peru has plans to dam it's rivers in the mountains and turn it's deserts into farmland.

Puente Freyne is a three span, 400 ft long deck truss supported on hammerhead piers and seat-type abutments. The bridge abutments are tall in order to support the deep truss while still providing a roadway at deck level.  The piers sit in the river suggesting that cofferdams were used or perhaps the river was diverted during construction of each pier.

This truss bridge is different from Puente Montalvo in many ways. In Puente Montalvo the truss had posts between the 'downward-pointing' triangles while this bridge has posts between the 'upward-pointing' triangles. Puente Freyne is a deck truss while Puente Montalvo is a through truss. Also, this truss is old and rusty while the truss for Puente Montalvo is new and freshly painted.
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