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 STRUCTURAL REQUIREMENTS
The modular structure of the maintenance hangar should be a steel frame system. Use of a
column free roof structure over the hangar bays allows for maximum maneuverability of aircraft
within the hangar as well as flexibility for future changes in base loading. The hangar should be
designed to use prefabricated components to the maximum extent practicable.
Main Structural Framing Systems
The selection of the main structural framing system must balance the often competing needs of
the other design disciplines as well as the needs of the future occupants, owners and maintenance
activities.
Cantilevered System
A cantilevered system supports the entire weight of the roof structure, as well as superimposed
loads, from the rear wall of the hangar bay. Lateral load support is provided by the side and rear
walls.
The system is advantageous in that it provides a column free building face towards the aircraft
flightline. This maximizes the usable flightline frontage while decreasing the number of
obstructions to aircraft movements. Additionally, the system provides the maximum flexibility
for structural expansion to either side of the hangar. However, if future expansion is anticipated,
other disciplines must consider such expansion in their design development.
Disadvantageously, a cantilevered system is an inefficient method for supporting loads, is prone
to larger deflections than other systems and is more difficult to erect. Thermal cycles are also
more likely to result in larger deflections, but will not result in thermal stresses unless the system
is restrained in some unconventional manner. Additionally, the landward side of the facility
must have some provision for tension anchorage of the rear of each cantilever. This anchorage
may be in the form of massive dead-load or tension earth anchorages (typically tension piles).
Therefore, a cantilevered system also requires a more elaborate foundation.
Design documents for a cantilever system need to carefully consider the effect of erection
sequencing, actual versus predicted dead loads and environmental conditions during the
fabrication and erection. Additionally, the designer must consider the possibility of load reversal
on the main supporting elements as a result of high uplift forces.
Header Truss System
A header truss system spans entire flightline face of the building and either rests upon towers at
each flightline corner of the building or is continuous to the foundation. The remaining walls of
the hangar are conventionally framed. Lateral support is provided through the walls and the truss
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