Pennybacker Bridge

The Percy V. Pennybacker Jr. 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." Due to its arched weathering-steel bridge and the rolling hills on its northern side, this structure is regarded as a scenic route in Texas.

In 2001, 48,000 vehicles crossed the bridge daily. Ten years prior to this, 22,000 vehicles had crossed the bridge daily.

Specifications
The bridge is constructed such that no part of the structure touches the water 100 ft below. The bridge is 1150 ft long with a 600 ft 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 ft 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.

Aesthetics
The steel bridge has a uniform weathered rust finish allowing the bridge to blend in with the surrounding hills and lake.

Planning
Originally envisioned as a western circular road, Loop 360 began planning in 1962. As part of Loop 360's construction, a contractor was selected to cut into the rock at the site of the future bridge and approach roads due to the area's terrain. This rock debris was deposited along the lakeshore at the site of the proposed bridge, raising environmental concerns. At one point, the Austin Navigation Board considered legal action against the contractor responsible for the rock debris.

Throughout the design and build process, concerns were expressed by elected officials and residents over the environmental effects of such a bridge, particularly the possibility of concrete pillars being driven into the lakebed. The bridge was redesigned in 1978 as a tied-arch bridge to avoid placing pillars into the water.

The contract for the bridge was let in late 1979.

Construction
The 600 short tons (544,311 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 3400 ST of concrete. The finish was sandblasted to ensure even weathering for an amber patina. The construction was coordinated by Clearwater Constructors (Hensel Phelps) of Denver, Colorado. Ed Westall was the project coordinator, Buddy Johnson was the project supervisor and David W. McDonnold was the bridge designing engineer. The bridge cost US$10 million to build.

Additionally, a local metal fabricator, Beck Tool & Manufacturing (Thomas L. Beck, Owner) was contracted to machine many of the critical components that anchor the cables suspending the roadway. Major structural steelwork was finished by July 1982

Completion
The bridge was dedicated officially November 29, 1982 by Austin mayor Carole McClellan and other public officials and opened for traffic December 3, 1982.

Naming


The bridge is named for Percy V. Pennybacker Jr., who designed bridges for the Texas Highway Department and was a pioneer in the technology of welded structures. Pennybacker, a resident of Austin since 1939, worked for the department for over 20 years before retiring in 1957.

Awards
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.