Speed of construction was certainly the primary factor for the air traffic control tower constructed on the eastern edge of the St. Augustine-St. Johns County Airport. Tilt-Up was selected as the solution because of the method’s ability to meet demanding schedules and budgets, and even more important – durability and resistance to everything from hurricanes to bombs. Previously, the typical construction method for aviation towers has been cast-in-place concrete, reinforced masonry, or a combination of the two; however, Tilt-Up was adopted for this project to meet the schedule and budget.
The original design concept included four full-height panels for the tower. But, the size of crane necessary to erect the huge panels, as well as the limited bracing area, necessitated an alternative solution. As such, the panels were divided vertically, which created eight 12-inch thick panels approximately 25-feet wide and 20-feet tall for the tower. Each panel weighed approximately 85,000-pounds each. Innovation was not limited to the design process, but applied during construction as well.
The first four panels were tilted into place, and then two concrete floors – constructed on the ground – were slid down into place, one at the 10-foot mark and the other at 20-feet. The next four panels were then tilted into place on top of the original four panels and braced to the second floor slab. The remaining two floors slabs were then dropped into place at 10-foot increments. The benefit to this system is the use of a smaller crane and braces, as the braces never had to handle more than 20-feet of panel. The cap – the control tower also was constructed on the ground – was simply lifted as one piece into place.
The tower was designed for maximum durability – to include 125 mile per hour wind load and exposure category D with an importance factor of 1.15, meaning that this tower should not only stay intact during a hurricane, but operational. Exterior stucco and roof colors were selected to blend in with the architecture of the city and surrounding community.
St. Augustine, FL 32095
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