UFC 4-211-01N
25 October 2004
4-5.2.1
Hangar Doors. Hangar door guide systems are normally sized to
allow total roof truss live load deflection not to exceed 200 mm (8 inches). The
designer of record is responsible for coordinating the total anticipated roof
deflection with several potential door guide manufacturers to ensure that an
economical system is selected. For cantilever roof systems, the hangar door
guide system should have adjustment capability to allow for final leveling after all
loads are in place.
4-5.3
Static Determinacy. Designers are cautioned that the basic
structural elements of a truss system should be "statically determinate" during the
adjustment phase (to avoid introduction of large and often unpredictable stresses
into a constrained system) unless a careful investigation has been made into the
resulting load condition.
4-5.4
Miscellaneous Considerations. Provide a means to "lock in" the
final adjusted configuration once the system has been leveled. If high strength
bolts are used, ensure that they are fully tensioned. The use of load indicating
washers in final bolted assemblies of the principle load carrying members is
encouraged. The use of load indicating washers allows for more meaningful
inspection of the primary connections at a later time. In all cases, bolted
assemblies that require fasteners to be loosened in order to adjust the structure
should have their bolts discarded and replaced before the construction is
complete.
4-5.4.1
Failure Mechanism. Single points of failure are undesirable in any
facility but are historically not uncommon in long span-steel structures. Pay
particular attention to the connections between major structural elements (truss
supports, cantilever anchors, etc). The designs should include secondary or
backup load paths should the primary system be damaged.
4-5.5
Construction and Erection. Hangar construction involves the
creation of a long-span, column-free space. These requirements complicate the
erection of the building and make the steel erection contractor a much more
important partner in the process than is typical of most government construction.
While the structural engineer is typically advised to avoid interfering with the
means and methods of the construction professionals, he should have an
understanding of the consequences that accompany any chosen erection
method. Two general approaches are applicable to the erection of large hangar
bays, ground assembly with heavy lift and aerial assembly with shoring towers.
4-5.5.1
Ground Assembly with Heavy Lift. While not unique to hangars,
lifts of pre-positioned, pre-assembled hardware weighing 27,000 to 45,000 kg (30
to 50 tons) are uncommon in most construction and typical of hangar
construction. Ground construction is typically the most common means selected
by contractors. Large cribbing is set immediately adjacent to the lift location and
leveled. Shims are set to adjust for elevation differences and to establish the
proper camber. The structural element is then constructed on top of the cribbing.
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