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Torch Tower

3As Sanfrancisco Pic 6 High Res

Curved metal panels accentuate shape of torch-inspired control tower

San Francisco International Airport's (SFO) air traffic control tower was designed to resemble a torch. Paul Kim, AIA, NCARB, is project manager at HNTB Corp.'s San Francisco office, which was the master architect for the project. "[The control tower] reflects the SFO brand as an iconic symbol that is both elegant and timeless in approach," Kim says. "This idea is manifested in the sweeping torch form and is the impetus for opening of the tower shell to expose the core with a backlit glass façade, which greets passengers arriving along the upper-level roadway and SFO's AirTrain."

Photo: John Swain Photography; Courtesy of 3A Composites USA Inc.Curtis Fentress, FAIA, RIBA, president, CEO and principal-in-charge of design at Denver-based Fentress Architects, the architect of record for the project, says the torch design is reminiscent of the historic pier torches used in the 1800s to guide ships to port in San Francisco Bay. "The tower was designed as an iconic symbol for the airport," he says. "It needed to be a long-standing building that was dramatic in form to serve as an airport logo, but also symbolic of stability for passenger flights."


In Plain Sight

The control tower is located between terminals 1 and 2. The project also included a three-story, integrated facility building for the Federal Aviation Administration (FAA) and other personnel, two walkways that connect to the two terminals and renovations to the boarding area C entrance in terminal 1. One of the two walkways is a secure connector bridge with unobstructed views of the runways, a rest area and adjoining yoga room.

Kim says the design team saw an opportunity with the control tower's location. "Unlike towers at most airports, the SFO tower is located immediately adjacent to drivers and pedestrians," he says. "We wanted people to experience the tower up close as well as from afar."


Amazing Glazing

The 221-foot-tall, 5,652-square-foot control tower is a vertical, self-centering, post-tension concrete structure clad with curved metal panels and features a vertical, illuminated 147-foot-tall glass band on its west façade. In addition to serving as an iconic symbol for SFO, it was designed to provide maximum sightlines, withstand Richter magnitude 8 earthquakes and accommodate electrical equipment.

The control tower has an offset cab with a cantilevered roof and windows, which provides air traffic controllers with an unobstructed 270-degree view of runways and taxiways. Additionally, the control tower features skylights and an open-core design, which allows for views up through the tower and of cascading lighting.

Auburn Hills, Mich.-based Guardian Industries Corp. coated glass to produce its SunGuard SNX 62/27 and sent it to Burnaby, British Columbia, Canada-based Garibaldi Glass Inc., which manufactured it into insulated glass units (IGUs). Wausau, Wis.-based Wausau Window and Wall Systems fabricated its systems with the IGUs.

Livermore, Calif.-based Architectural Glass and Aluminum Co. (AGA) installed more than 4,000 square feet of Wausau Window and Wall Systems' four-sided, silicone-glazed curtainwall including SuperWall 8250 Series curtainwall, INvision 7250- UW Series unitized curtainwall and 7250 Series BHM curtainwall for the control tower. Additionally, AGA installed Wausau Window and Wall Systems' INvent 3250i Series in-swing casement thermal windows and Walker, Mich.-based Tubelite Inc.'s ForceFront Blast entrance systems.

Mark Costanzo, PE, project manager at SFO, says the LED lighting on the control tower's façade can transform it to recognize holidays and special events. "The tower lighting can be changed based on the mood of the airport," he says.


Curving Façade

Photo: John Swain Photography; Courtesy of 3A Composites USA Inc.Kim says the control tower's sleek façade is contextual with other airport structures but does not match them. "The intent was to provide a tectonic and elegantly detailed façade with a subtle but dynamic skin with spiraling aluminum panel joints around the conical surface," he says. "The shimmering skin adhered perfectly to the complex geometry of the tower. It is both fresh and unique in its fabric-like form while simultaneously linking you back to images of airplane fuselages and turbines and other metal-clad buildings at SFO."

North Vancouver, British Columbia-based Keith Panel Systems Co. Ltd. spent four months fabricating approximately 1,500 metal wall panels for the project. Rocklin, Calif.-based Pacific Erectors Inc. installed 10,000 square feet of Davidson, N.C.-based 3A Composites USA Inc.'s formable 4-mm Alucobond Plus aluminum composite material (ACM) in custom SFO Silver with Keith Panel Systems' KPS System A Pressure-Equalized Rainscreen System.

Wausau-based Linetec, applied Pittsburghbased PPG Industries Inc.'s three-coat Duranar Sunstorm XL Silver coating (70 percent PVDF) on the exterior of the aluminum framing for the curtainwall and entrance systems and a Duranar Sunstorm Galaxy Silver coating (50 percent PVDF) on interior-facing aluminum framing members.

"Alucobond was a material that could carry the shape of the building with an outward appearance that is sleek and dynamic," Fentress says. "It gives a futuristic quality to the building. Technically, it was able to create all of the joints and worked well with the complex structural engineering designed to ensure that this building will be there after a seismic event."


Custom Software

Photo: Daniel Lunghi Photography; Courtesy of 3A Composites USA Inc.Parametric modeling software and 3-D printed models were used to create the design. Keith Panel Systems spent approximately 1.5 years preconstruction planning and used Autodesk Revit building information modeling (BIM) software and architectural 3-D printed models to create a series of complex panel shapes. It created a series of nine panel assemblies and fabrication prototypes and two full-scale mockups. Field measurements were avoided by relying solely on 3-D modeling to fabricate the metal panels.

"When we started modeling and prototyping, we discovered the tower geometry was dictated by a set of very specific mathematic rules," Dalzell says. "This allowed us to confirm every dimension on each panel pulled from the model mathematically to ensure the panels would fit on-site. This was an exhaustive process requiring manual input and calculation of hundreds of points along the perimeter of each panel. While this process validated the theoretical model and was used in prototyping, it wasn't practical for fullscale production."

Dalzell says his company searched for software that would provide an automated flattening, but did not find one. "In the end, [Keith Panel Systems] employed a developer to build custom software for us," he says. "This was by far the toughest job we've ever done as a company, and the most extreme in terms of geometry and modeling. Every single panel was built from the mathematically corrected Revit model without relying on field dimensions. That's an incredible testament to the capability of BIM-based construction."


Outstanding Successor

The LEED Gold-certified project features sustainably produced finish materials, a roof garden, natural daylighting, programmable LED lighting, photovoltaic panels, energy-efficient HVAC systems, low-flow plumbing fixtures and electric vehicle charging stations. Construction started in 2012, the FAA began installing electrical equipment in July 2015 and the control tower was operational in October 2016.

Credit for photos 1, 2: John Swain Photography; Courtesy of 3A Composites USA Inc.
Credit for photo 3: Daniel Lunghi Photography; Courtesy of 3A Composites USA Inc.


Air Traffic Control Tower at San Francisco International Airport, San Francisco
Owner: City and County of San Francisco
Design-builder: Hensel Phelps Construction Co., San Jose, Calif.,
Master architect: HNTB Corp., San Francisco,
Architect of record: Fentress Architects, Denver,
Glazing installer: Architectural Glass and Aluminum Co. (AGA), Livermore, Calif.,
Glazing systems finisher: Linetec, Wausau, Wis.,
Metal panels installer: Pacific Erectors Inc., Rocklin, Calif.,
Structural engineer: Walter P Moore, San Francisco,
Coatings: PPG Industries Inc., Pittsburgh,
Glass fabricator: Guardian Industries Corp., Auburn Hills, Mich.,
Glass manufacturer: Garibaldi Glass Inc., Burnaby, British Columbia, Canada,
Metal panels fabricator: Keith Panel Systems Co. Ltd., North Vancouver, British Columbia,
Glazing systems: Wausau Window and Wall Systems, Wausau,
Metal wall panels: Alucobond by 3A Composites USA Inc., Davidson, N.C.,
Storefront: Tubelite Inc., Walker, Mich.,