CEMP-ET
TI 809-30
1 August 1998
4. General.
a. Definition. A Metal Building System is defined by MBMA as "a complete integrated set
of mutually dependent components and assemblies that form a building. It includes the
primary and secondary framing, covering, and accessories, all of which are manufactured to
permit inspection on site prior to assembly or erection". In simpler terms, it is a steel frame
building that typically consists of the following metal components:
Roof Sheeting
Wall Sheeting
Girts
Frames (including side wall columns)
Columns
Endwall Beams and Columns
Flange Braces
Longitudinal Bracing
Connections
Screws and Bolts
Other non-structural parts
When assembled, all of the parts form the shell of a complete structure. All components are
typically designed, fabricated, and furnished by a single manufacturer based on owner
identified requirements. They are delivered to the job site where they are assembled by a
structural steel erector. The general contractor, erection contractor, building supplier, or other
agreed upon party may act as the erector. Erection normally uses field-bolted connections
with little or no field welding. Primary components, such as columns, beams, and girders, are
typically fabricated from plates, are shop welded, and are optimized for the specified loading
conditions. Webs of beams and columns are normally tapered to conserve material in areas of
low stress. While Metal Building Systems with tapered rigid frames are the most common,
other types of framing are also in common use: single span self-framing (no frame), multiple-
span beam and column frames, trussed column and girders, trussed rigid frames, continuous
beam frames, columns with tapered girders, etc.
b. Pre-Engineered Buildings. Several years ago Metal Building Systems were commonly
referred to as "Pre-engineered Buildings". The term is still popular in the building trades
despite efforts by MBMA members to change the culture. "Pre-engineered Building" was an
appropriate name because it described the procurement process in place at that time. Building
manufacturers hired structural engineers to design a series of standard building modules for
different wind loading. The modules differed in eave height, building width, and roof slope.
The modules could then be joined to create buildings of practically any length. An owner
would review the catalog, select a building with a footprint and interior height that most closely
matched the requirements, and place the order with the supplier. The manufacturer would
then fabricate the parts based on the standard design drawings on file and ship the building to
the owner's site. Erection would be by a general contractor or by an erector that worked with
or for the supplier. This approach is quite different from the modern process. Today, most
manufacturers use proprietary computer programs for design and provide a custom designed
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