Phoenix-Mesa Gateway Airport has experienced increased air traffic in recent years, and with plans to expand the airfield, it was necessary to build a taller, state-of-the-art traffic control tower (ATCT). The new structure meets all current Federal Aviation Administration (FAA) criteria and replaces the original tower constructed in 1968 when the site was an Air Force base.
The 194-ft-tall ATCT includes a 500 ft² control cab with room for eight controller positions. The lower tower shaft is unoccupied, accommodating vertical circulation (stair and elevator tower) and various mechanical, electrical, communications, fire protection, and navigational aids utility risers. The ground floor level houses FAA electronic equipment and storage rooms, the main mechanical and electrical service entrances, the entry vestibule, and the elevator lobby.
The tower’s seismically resistant, 12-sided precast concrete shaft is composed of precast concrete panels with integral color and a medium sand-blasted finish. Intermediate floor slab and stair construction also have a precast concrete design, with the upper tower expanded ring construction employing steel framing with insulated metal panel cladding and high-performance insulated glazing bands. Two structures, designated as the bulge and the cap, sit atop the tower.
The new ATCT is 65 ft taller than the old tower and will provide twice the cab space. In addition to the eight controller stations, there is a staff break room, meeting and training spaces, and offices for the controller in charge and the air traffic manager.
Precast concrete was selected to meet the stringent FAA requirements for building drift, and to expedite the overall construction process. In addition, all interior components (floors, walls, and stairs) were redesigned with precast concrete to speed installation. As a result of this effort, only one trade was on site for the construction of the shaft element.
Typically, ATCT exterior walls are constructed using five precast concrete modular section pieces, which are shipped horizontally. In an effort to reduce the quantity of exterior spliced connections, this project was designed and constructed with only three exterior precast concrete sections, which were shipped vertically to the jobsite. The reduction in the number of pieces resulted in a shorter erection sequence. Precast concrete slabs were used at each floor of the tower. Each floor consisted of three floor slabs that would bear on angles welded to embeds cast into each exterior and interior precast concrete wall. Precast concrete stairs provided direct access to the tower during erection. Separate precast concrete landing slabs were used due to the special shape required from the geometry of the exterior ring walls. Erection crews used two interior hydro mobile scaffolding units, which were each customized with a platform that would fit in the mechanical and air shafts. The units had to be built up as construction went vertical. These units eliminated the need for traditional scaffolding and allowed the grouting, welding, and erection crews to work safely and reach all areas of the tower during the tower installation.
The construction of this ATCT required exacting precision and tight tolerances. The use of precast concrete facilitated the critical coordination of the connection between the tower and the steel bulge and cap, improved on-site safety, and shortened the project schedule.