Maintaining History in Central Georgia

A multi-year design and construction project at Robins AFB must balance the need to replace the roof on an historic World War II-era aircraft maintenance hangar against the responsibility to allow the facility’s mission critical work to continue unimpeded.

 

By Robert Durham, AIA, NCARB, LEED AP BD+C, M.SAME, and Terry Allen, P.E., M.SAME

 


 

In September 1941, the War Department began construction of an Army Air Corps Depot in central Georgia that was later to become Robins AFB.

Spurred on by the surprise attack on Pearl Harbor, the U.S. government dramatically increased the rate of construction of the depot by employing 6,600 workers in order to finish construction as soon as possible. This extraordinary effort led to Building 125, the Aircraft Repair Building, being completed significantly ahead of schedule in August 1942. The facility became known as the Maintenance Hangar, which is its current official designation.

Today, Robins AFB contains a number of historically significant structures that are eligible for inclusion in the National Register of Historic Places. And after 70 years of continuous use, some of the build­ings are showing their age.

 

NECESSARY RENOVATION
Four years ago, the U.S. Air Force desper­ately needed to replace the roof on Building 125. Due to the hangar’s age, it also would be necessary to replace the sprinkler system, construct a new drainage system and mitigate a substantial volume of hazard­ous waste. Because the hangar continues to support mission critical activities, that responsibility would need to continue unimpeded during any reconstruction.

Mason & Hanger, an architecture and engineering firm based in Lexington, Ky., was hired by the U.S. Army Corps of Engineers to prepare the preliminary design documents for a design-build contract. The request for proposal was completed in December 2012 and construction of the project is ongoing.

 

Robins AFB maintenance hangar project

South facade shows Art Deco details and roof of Maintenance Hangar, Building 125, at Robins AFB before renovation. The hangar, built between 1941 and 1942, provides space for mission critical large aircraft maintenance repair. The Air Force has commissioned a new roof be built to replace the aging roof in place for 70 years. PHOTOS COURTESY MASON & HANGER


 

The 604,000-ft² hangar is the only building at Robins with Art Deco design elements. These features include panels and pylons of stucco and concrete in its corners and central bays. The age of the hangar, its legacy and its unique design elements, however, are just part of the challenge.

 

CONSTRUCTION REQUIREMENTS

In order to provide for the safety of work­ers and the associated aircraft, maintenance operations are prohibited in all construc­tion areas. The Air Force has required, because mission essential large aircraft maintenance is conducted at the hangar, that it remain operational throughout the entire construction period.

Since the hangar is comprised of four separate bays (or docks), the construction schedule has been carefully phased to allow the contractor to work in only one dock at a time. This allows aircraft maintenance operations to continue as required in the other three areas.

 

STRUCTURAL ANALYSIS

The existing roof system for each of the four docks consists of straight-line elements that make up barrel-shaped vaults.Each vault is covered with corrugated metal panels connected to C-channels supported by structural steel girders and columns. A low-sloped, built-up asphalt roof is now covering the central work area between the docks.

Due to the building’s 70 years of wear and tear, Mason & Hanger was responsible for conducting an analysis of the roof to determine its structural integrity. Without any drawings or other as-built informa­tion, the firm spent several weeks on-site gathering information to be used in a finite element analysis. Once that was completed, a structural capacity could be determined to assure that the existing structure could safely support the weight of the new roof.

 

HAZARDOUS MATERIALS

Other issues identified during the design charrette included widespread drain­age problems and contamination from hazardous material. These all needed to be resolved as prescribed by the preliminary design documents.

A study was commissioned to identify the hazardous materials present in the building and devise a plan to dispose of them. The primary materials found on-site included lead paint and asbestos in the Galbestos roof and the siding panels as well as drywall joint compound in the building’s north annex. The Galbestos material also contained polychlorinated biphenyls.

To remove lead paint in the building’s structural frame, the contractor is required to sandblast the steel framing members and decking. As the sand strikes the lead paint, it becomes contaminated and must be disposed of as hazardous waste. After removing the paint, the bare steel is exam­ined to determine if there is any corrosion or other deterioration that would need to be repaired. The management and disposal of hazardous waste has followed the U.S. Environmental Protection Agency regu­lations established in the 1977 Resource Conservation and Recovery Act, which regulates the management, handling and disposal of hazardous materials.

 

Robins AFB maintenance hangar projectDeterioration of paint is visible on the interior steel frame and roof of Building 125. The existing roof over each of the four aircraft maintenance bays is a barrel-shaped vault, formed by multiple straight-line segments. To facilitate construction and eliminate future problems with thermal joint movement, a new roof structure has been developed, consisting of a continuous, uniformly supported arc.


 

ROOF SYSTEM DESIGN

The existing roof over each of the four aircraft maintenance bays was a barrel-shaped vault, formed by multiple straight-line segments. In order to facilitate construction and eliminate future problems with thermal joint movement, a new roof structure has been developed. It consists of a continuous, uniformly supported arc. Standing-seam metal panels running from eve-to-ridge were specified to prevent future leaks and increase durability.

The orientation of the barrel vault roofs has also posed a unique drainage challenge, as adjacent barrel vault roofs were aligned so that water from two vaults cascaded down into the same drainage trough. This flat trough, without sufficient slope to carry the water to the drains, was prone to exces­sive ponding and leakage. To eliminate this problem, the troughs were reconfigured to provide additional slope and the internal drains were enlarged to handle more runoff and prevent excessive ponding.

The request for proposal requires the contractor to inspect all of these systems with a remote-controlled camera to ensure proper functioning of the existing storm water drainage system inside the building and underground. In addition, the new roof design documents state that the contrac­tor must provide a secondary drainage system—something that was not required in 1942. This secondary drainage system also will help control rainfall events outside the original design perimeters.

 

PROJECT TIMELINE

Due to the Air Force’s maintenance schedule, construction work can only proceed at a fixed rate, one dock at a time. To maintain continuity, one contractor has been selected for the entire $50 million project, with a phased construction sched­ule extending out over almost six years.

When the project is completed in 2019, the drainage problems will be eliminated, the hazardous materials will be mitigated, and Robins AFB will again have a modern large aircraft maintenance facility, just as it did in August 1942. And the work all will have been achieved through preserving and reusing a histori­cally significant structure that can now be expected to serve the nation for another 70 years.

  


 

Robert Durham, AIA, NCARB, LEED AP BD+C, M.SAME, is Architect, and Terry Allen, P.E., M.SAME, is Project Manager and Director of Quality Management, Mason & Hanger. They can be reached at 859-280-3520, or This email address is being protected from spambots. You need JavaScript enabled to view it.; and 859-252-9980, or This email address is being protected from spambots. You need JavaScript enabled to view it., respectively.