Quantcast Seismic loads

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(1) Factored Load Combinations
Any load case in which dead load is factored with a coefficient exceeding unity, that portion of
the dead load serving to resist overturning should be factored with a 0.9 coefficient.
(2) Service Load Combinations
Any load case in which dead load is factored with a coefficient exceeding unity, that portion of
the dead load serving to resist overturning should be factored with a 0.6 coefficient.
Wind Loads
Refer to American Society of Civil Engineers (ASCE) 7, Minimum Design Loads for Buildings
and Other Structures to quantify and distribute wind loads to the building.
Wind load on main building wind force resisting system should be determined on the following
two conditions:
(1) Hangar doors fully open for winds up to 96.6 kph (60 mph).
(2) Hangar doors closed for winds above 96.6 kph (60 mph) up
to the maximum wind velocity for the geographic area.
Hangars are prone to large eccentricities between centers of wind pressure and centers of rigidity
(especially cantilevered hangars). Even unfactored loads resulting from this eccentricity may be
significant. The designer is cautioned to consider this eccentricity and to locate the center of
rigidity as near to the center of applied force as practical by careful arrangement of the lateral
load resisting elements.
Seismic loads
The designer should consult the references listed (1 below) for seismic design loads.
Additionally, seismic design criteria may impose significant constraints upon the structural
frame, not only in the loads applied but also in the fundamental choice of framing system (2
below). For instance, an STMF system is limited to a span of 20 meters (65 feet). A
combination of site condition, design approach and structural layout will determine the AISC
criteria.
A poor selection of framing, arrangement of bracing or large asymmetries may result in
expensive connection fabrication and testing requirements or outright prohibition of the
fundamental design. The facility designers are cautioned to investigate the seismic issues early
in the design phase and plan the building's geometry and structure accordingly.
Hangars are prone to large eccentricities between centers of mass and centers of rigidity
(especially cantilevered hangars). Regardless of the structural system, the unfactored loads from
this eccentricity may be significant.
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