Friday, January 24, 2014

Pennybacker Bridge, Austin:

Pennybacker Bridge

The Pennybacker Bridge in Austin, Texas, is a through-arch bridge across Lake Austin which connects the northern and southern sections of the Loop 360 highway, also known as the "Capital of Texas Highway." The road is widely considered one of the most scenic urban drives in central Texas, in large part due to this arched weathering-steel bridge and the rolling hills that flank the road. In 2001, 48,000 vehicles crossed the bridge daily. Ten years prior to this, 22,000 vehicles had crossed the bridge daily.
The steel bridge has a uniform weathered rust finish allowing the bridge to blend in with the surrounding hills and lake. The 600,000,000 pounds (272,000,000 kg) of steel for the bridge were produced in Japan. The bridge structures were fabricated in Ulsan, Korea by Hyundai Heavy Industries. The steel structures were shipped on the Jundale freighter to the Port of Houston and then trucked to the bridge site. The bridge was erected by Bristol Steel of Bristol, Virginia. The roadway surface is built from 3,400 short tons (3,000,000 kg) of concrete. The finish was sandblasted to ensure even weathering for an amber patina. The construction was coordinated by Clearwater Constructors of Denver, Colorado. Ed Westall was the project coordinator, Buddy Johnson was the project supervisor and David McDonnold was the bridge designing engineer. The bridge cost US$10 million to build.
The bridge is constructed such that no part of the structure touches the water 100 feet (30 m) below. The bridge is 1,150 feet (351 m) long with a 600-foot (183 m) central arched span. This design keeps Lake Austin free from support columns because the recreational lake (really a dammed stretch of the Colorado River) is popular with boaters and waterskiers. The untied arch suspension span is suspended by 72 steel cables. At the time of its construction, it was only the second bridge of its design in the world.
The bridge has four lanes, two in each direction, separated by a middle barrier wall. The bridge also has a 6-foot-wide (1.8 m) bike and pedestrian lane. The bike access on the bridge is one reason for Loop 360's popularity with cyclists. The south approach provides a turnaround under the bridge along with lake access for public boating.
The bridge won first place in the 1984 Federal Highway Administration's Excellence in Highway Design competition. In 1992, the Austin members of the Consulting Engineers Council of Texas were surveyed and selected the bridge as the most innovative example of Austin architecture.



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