Fieldale, VA, 2001
53’ span x 3’ rise x 22’ wide Hy-Span Bridge
Designed to carry gross vehicle weights of 204,000 lbs
Unit weight – 58,000 lbs per section
7 Hy-Span units and curbs installed in 5 hours
Boxley Materials, a supplier of quality construction materials, needed to relocate its truck scales as part of the Fieldale, Virginia plant expansion. The routing of trucks through the new scales included crossing a small stream located between the scales and the scale house. Boxley wanted a single clear span structure to minimize impact on the waterway and aquatic environment. The clear span also reduced expensive and time consuming permit acquisition. The site required a structure with a 50 foot span (X) 3 foot rise (X) 22 foot width. On a previous plant expansion, Boxley had utilized a triple cell Hy-Span structure from Permatile. Pleased with its first Hy-Span structure, Boxley contacted Permatile to provide a solution to the task at hand.
The stream crossing at the Boxley site required Permatile engineers to design a 50 foot single span unit with only a 3 foot clear vertical rise. Another challenge was the vehicular live load for the bridge. Permatile recommended use of the Hy-Span Bridge System- a three sided, flat deck, rigid frame system. For almost two decades the Hy-Span System has been used successfully on DOT, municipal, and private projects throughout the Mid-Atlantic region.
The precast units were designed to support live loads generated by highway use tandem and tri-axle dump trucks as well as fully loaded, off-highway haulers with gross vehicle weights approaching 204,000 pounds. Final design also included a three-inch asphalt overlay. The resultant maximum loads were approximately 30.5 kips per linear foot vertically and 15.5 kips per linear foot horizontally, far exceeding normal loading for standard highway bridges.
When geotechnical site investigation indicated less than desirable results for the bridge foundation, Permatile engineers helped design an H pile foundation system. The piles would be topped off with a reinforced concrete cap designed to accept the abutment walls of the precast rigid frame units.
Seven precast rigid frame units with a typical width of 3.14 feet, an overall length of 53.33 feet, weighing almost 58,000 pounds each, were shipped to the site for the installation on the cast-in-place foundation. Due to the extreme mass of each precast unit, special procedures for handling and placement were necessary on site. The general contractor installed all seven Hy-Span units and curbs within 5 hours utilizing only a 5 man crew from start to finish.