On September 15, 2004, the Air Force Memorial Foundation held a groundbreaking ceremony on a three-acre site at the Naval Annex overlooking the Pentagon in Arlington, VA for the long anticipated Air Force Memorial. Centex Construction, LLC, was awarded the contract to provide preconstruction and construction services on the $30 million project. Centex, represented by their Washington, DC, division, was selected over five other firms competing for the project. Bevan Mace, ’97, ’01g, project manager and Kevin Engel, ’07, project engineer with Centex, along with fellow PSU alumnus Mike Phillips (Civil Engineering), vice president of operations, and Bhavin Patel, current CE undergraduate student on internship, were proud to be part of this exciting and historic construction project.

Designed by James Ingo Freed, an internationally recognized architect of Pei Cobb Freed and Partners in New York, the design includes three stainless steel spires that stretch skyward in graceful arches symbolizing flight, as well as the precision “bomb burst” maneuver performed by the United States Air Force Thunderbird Demonstration Team. The three spires also represent the three core values of the Air Force - integrity first, service before self, and excellence in all that is done.

The memorial also features an Absolute Black granite paved parade ground featuring an 8-foot tall bronze sculpture and a 9 ft. x 10 ft. illuminated glass Contemplation Wall. The sculpture depicts a four person honor guard that was created by the distinguished sculptor, Zenos Frudakis. The glass Contemplation Wall was constructed by laminating five layers of ½” Starphire glass and then carved to depict planes flying in the “missing man formation,” a final tribute paid to fallen airmen. The parade ground is flanked by two granite inscription walls which are each approximately 11’ high and 60’ long which were constructed using a 12” thick JetMist granite monolithic support wall faced with 2.5” thick Absolute Black granite panels. The JetMist granite was quarried in nearby Culpepper, VA, the Absolute Black was from Italy. A stone seating area, entrance gate, extensive stonework in paving and walls, one guard house and a stone-clad service building are also included in the design of the memorial.

Bevan Mace (shown right climbing at the 200 ft. level of one of the spires) discussed some of the unique engineering challenges that were associated with the construction of the arched spire structure. Each spire is constructed of triangular arched sections fabricated with ¾ inch-thick plate stainless steel skin with a bead blast finish. The three spires extend vertically to 270 feet, 231 feet and 201 feet. The spire structure is supported by a system of concrete foundations that include concrete caissons, concrete pile caps and concrete grade beams. The caissons are three feet in diameter with a six foot belled base. The pile caps are approximately 23 feet wide and eight feet deep and range in length from 32 feet to 56 feet. The pile caps are connected by a continuous triangular grade beam, approximately eight feet wide by 16 feet deep and with a perimeter of about 300 feet. The spires are connected to the concrete foundations with a two and a half inch base plate and anchored by one and a quarter inch post-tensioned reinforcing steel bars. (shown above) Once the base section (about 40’ tall) of each spire was set, two layers of #11 reinforcing at 6” o/c was installed on each face and the section was poured with 12,000 PSI concrete. In total, fifteen sections, from 40’ to 75’ in length, were erected to construct the spires; the heaviest section weighed about 110,000 pounds. The total weight of the spires including stainless steel, reinforcing steel and concrete, is approximately 7,300 tons (5,000 tons below ground, 2,300 tons above ground). The spires were installed with the use of a 300-ton Manitowoc “ringer” crane. (shown left) Mace reported that the single biggest challenge on this project was the welding, polishing and finishing of each section of the spires. Each section was made using individual flat plates that were milled, polished, cut and then rolled before it got to the fabricator’s shop. The fabricator constructed temporary falsework (same length and size of each spire) to support each face of the section while it was being welded together. The fabricator had to experiment with various variables (e.g., wire type, size, shielding gas) when welding the faces together to make not only a sound structural weld but also one that minimized distortion which ultimately was critical to a good aesthetic finish once a section was completed. All the welds had to pass radiographic examination; once a section had completely passed then the fabricator used custom tools to grind down and polish the weld prior to finishing. Of course, this entire process had to also be completed on site, high above the ground, when the sections were joined together. (right and below)

A problem inherent in the design of the tall spires is the sway caused by strong wind. Initial wind-tunnel tests conducted on scale models of the spires, verified that they were susceptible to structural failure due to wind conditions that could cause galloping. To mitigate the swaying the structural engineering team used a series of multiple ball-in-box mechanisms within each spire. Each mechanism consists of an octagonal stainless steel box lined with a synthetic dampening material (Sorbothane) and houses a 20-inch, 2,000-pound lead ball. When the spires begin to sway, the free-rolling lead balls hit the dampening material on the sides of the box which absorb the energy and help to reduce the swaying effect. Arup’s Advanced Technology Group in the United Kingdom developed this custom system and has fine-tuned the precise dimensions and position of each of the boxes within all three spires to ensure that an appropriate level of damping is achieved. One damper box was tested in Buffalo, NY prior to erection and following construction each spire was individually tested to verify performance of the dampening system.

The United States Air Force Memorial was officially dedicated by President George W. Bush at an onsite ceremony held on Saturday, October 14, 2006. The event was open to the public and was attended by numerous military top brass as well as several thousand spectators.

During his dedication speech, President Bush said,
“Building this memorial took a lot of talent and creativity and determination. Like the aircraft whose flight it represents, this memorial is an incredible feat of engineering. Like the country whose freedom it represents, this memorial is hopeful and optimistic. By its design, this monument raises our eyes toward the vast and open skies, and focuses our mind on the endless possibilities of human flight.”

The Memorial honors the millions of patriotic men and women who have distinguished themselves in the United States Air Force and its predecessor organizations, including the Aeronautical Division, the U.S. Signal Corps; the Aviation Section, U.S. Signal Corps; the Division of Military Aeronautics, Secretary of War; the Army Air Service; the Army Air Corps; and the Army Air Forces.

Mace said, “Everyone involved on this project was very proud to be a part of its construction because of the impact it has on a large number of people traveling into Washington DC – either from the air, from across the Potomac or on the Memorial grounds itself. Normally when we turnover a project to the owner they move in and go to work; on this project it was very different and gratifying to see all sorts of people, including kids, walking around and experiencing the Memorial in their own way.”