The organic architecture movement in Hungary grew in the late 20th century as a protest against the Brutalist architectural styles favored by the ruling Communist party. When current Prime Minister Viktor Orbán commissioned a landmark soccer stadium at the Puskás Academy, just outside of Budapest, he “was firmly committed to the concept of organic Hungarian architecture,” says Tamás Dobrosi, principal at local firm Doparum Architects.
The 3,400-seat Pancho Arena, which hosts league matches and
tournament games, maintains the style of the athletic academy’s campus, which
was master planned by Imre Makovecz, a prominent proponent of organic
architecture. The 130,000-square-foot arena harmonizes with the natural environment,
from the fan vaults that spread like tree branches to the use of timber as the
primary building material.
Like a forest canopy abutting a clearing, the roof cantilevers 43 feet over spectators and is supported by glulam columns rooted into concrete piers every 20 feet with the use of 36-millimeter-diameter threaded rods anchored 5 feet into the concrete and affixed with synthetic resin. These primary supports arc up and fan out, with steel elbow-bracket reinforcements. As the supports extend farther from the piers, their depths increase to accommodate the accumulating cantilevered load.
Secondary intersecting beams connect to the primary beams via
radial glulam crutches. The resulting hybrid timber-and-fan-vault construction is
based on gridshell principles.
In the first design iteration of the roof, modeled in ArchiCAD, nearly every support had a unique radius, which was cost prohibitive to manufacture. In their second pass, Doparum grouped members of a similar bending radius for more efficient milling, Dobrosi says. For example, the team revised all members that initially were 33 to 43 feet tall to have a bending radius of 38 feet, the average.
A CNC router cleared boreholes and slots for the heavy-duty screws and hardwood-peg joinery in the glulam members. The steel fittings that anchor the beams to the concrete piers resist the tension forces in the primary beams toward the roof’s open edge, and resist the compression forces in the beams toward the base of the roof.
In plan view, the roof was built in rectangular segments, with each section being self-supporting. Once the corners of the arena’s roof were completed, five carpentry teams simultaneously worked inward to construct the remaining sections.
In total, nearly 1,000 tons of wood were used to form the vaulted structure. Austrian timber manufacturer Rubner Holzbau manufactured about 80 percent of the GL28 and GL32 pine beams—both mid-grade varieties of glulam—and Hungarian specialty timber mill Sokon completed the remaining fabrication and construction. Structural engineer László Pongor analyzed the system's capacity.
Dobrosi is proud that the Pancho Arena was designed and
constructed by local firms. “Smaller firms may not have much big-project
experience,” he says, “but [we] had lots of diligence and enthusiasm.”