UFC 4-211-01N
25 October 2004
CHAPTER 4
STRUCTURAL REQUIREMENTS
4-1
GENERAL. Use a steel frame system for the modular structure of
the maintenance hangar. 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. Design the hangar to use
prefabricated components to the maximum extent practicable.
4-2
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.
4-2.1
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. Provide lateral load support by the side and rear walls.
4-2.1.1
Advantages. 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.
4-2.1.2
Disadvantages. 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
affecting door operation, 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). A cantilevered system also requires a
more elaborate foundation.
4-2.1.3
Considerations. Design documents for a cantilever system need
to carefully consider the effect of erection sequencing, actual versus predicted
dead load deflection and environmental conditions during the fabrication and
erection. Additionally, consider the possibility of load reversal on the main
supporting elements as a result of high uplift forces.
4-2.2
Header Truss System. A header truss system spans the 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
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