1 August 1998
(1) Collateral Loads are an estimate of the miscellaneous loading, expressed as a
uniform load applied to the entire structure, that account for small miscellaneous items such as
lights, ducts, etc., that are hung from the structural frame or secondary framing members.
Collateral loads should not be increased to account for heavy items, i.e., those with a mass
more than 25 kg (55 lb.) hanging from the framing, since that would impose a significant
penalty on members that do not support the heavy loads. Instead, large equipment should be
shown on the contract drawings and tabulated on the structural drawings with descriptions,
estimated weights (to be verified by the contractor), plan dimensions, drawing references for
locations, and any unusual access requirements. Secondary members should be increased
appropriately in size or number to support the heavier loads.
(2) Wind loads are frequently subject to miscalculation even by experienced engineers
and an error, if undetected, could result in costly redesign and resubmittal. Relying on code
references alone and allowing the manufacturer to calculate pressures may be safe for small
uncomplicated structures, but it is preferable to calculate pressures and illustrate the limits of
these pressures on the contract drawings for large complicated structures. The use of tables
and isometric drawings to illustrate all significant design pressures, the extent of all high
pressure areas, and the pressures for parts and portions of the structure along with their
tributary area limitations is recommended.
(3) Seismic loads rarely control the design of lightweight flexible steel structures.
These loads become more of a concern if rigid masonry or precast elements are attached to
the structure as cladding. ICBO-01 was chosen as the specification reference for seismic
loads since this commercial criteria is readily available to the manufacturers and closely
approximates the design guidance in TI 809-04.
(4) The foundations paragraph in the guide specifications contains written criteria the
contractor will use to design the building foundation. Additional supporting criteria, to include
required details of construction, should be shown on the structural plates of the contract
drawings. Examples include: details of integral slab footings, details of separate wall or
column footings, minimum thickness of slabs at edges, dimensions of turn-down portion of
slabs, details of hair pins or tie rods for lateral thrust resistance, etc.
(5) If Structural Standing Seam Metal Roofing is to be used on the structure, then
purlin spacing of 750 mm (30 inches) maximum at corner, edge, and ridge zones and at 1500
mm (5 foot) maximum for the remainder of the roof are required and must be clearly shown on
the drawings, or in the specification.
(6) Acceptable methods for resisting lateral loads include cross-bracing (X-bracing),
diagonal bracing, rigid frames, and wind columns. Metal shear wall bracing should only be
allowed for self-supporting structures procured under specification section CEGS 13121.
Bracing conflicts with doorways and other openings can be a problem. Bays and roof/wall
openings that must remain free of bracing should be shown on the architectural drawings.
(7) Metal Buildings are flexible structures that move under the application of wind,
seismic, and crane loading. Appendix A6 of the 1996 Low Rise Building Systems Manual
provides guidance and should be considered when specifying allowable drift in the
specification. The specifications engineer and design engineer must insure that the maximum
allowable frame drift is suitable for the proposed structure considering all details of