1 September 1999
METAL BUILDING SYSTEMS
10-1. INTRODUCTION. A metal building system is an engineered product furnished by metal
building manufacturers. The metal building can be selected from a catalogue of standard
designs or can be a custom design. Metal building systems, in general, consist of:
rigid frames which act as the primary vertical load carrying system and as a lateral
force system in the transverse direction,
rod or angle x-bracing for the roof truss diaphragm and for vertical lateral bracing in
the longitudinal direction,
girts to support wall system cladding and resist wind loads,
roof purlins to support a standing seam metal roof system and roof live , loads, and
an exterior cladding system.
Many variations in framing systems are possible, and many different wall-cladding systems can
be used including metal panels, brick veneer, masonry, and precast concrete wall panels.
Additional information on metal building systems can be found in TI 809-30, "Metal Building
10-2. METAL BUILDING OPTIMIZATION. The metal building system will be optimized, based
on ASCE 7 load and load combination requirements, to provide the lightest weight structural
system possible. The designer must determine if additional requirements related to
displacement, drift, durability, and redundancy should be written into the specifications to
assure the final design will satisfy short and long term performance goals including function,
durability, serviceability, and future expansion needs.. The major optimization occurs with
respect to the rigid frames. These frames are constructed of relatively thin plates that are
welded together. The frames use tapered webs with increased depth in the areas of high
moments. Web thickness and flange size are varied as needed. The rigid frame members are
designed with bolted end connections for easy field assembly. Most often the flanges are weld
connected to the web on only one side to reduce fabrication costs. The secondary members
including girts and purlins are cold-formed with a high strength to weight ratio.
10-3. BASIS FOR DESIGN.
a. Criteria. Specifications for metal building systems usually require that design be in
accordance with the Metal Building Manufacturers Association (MBMA), "Low Rise Building
Systems Manual," except that design loads and load combinations will be in accordance with
TI 809-01, "Load Assumptions for Buildings." Secondary members (purlins, girts, etc.) are
normally light gage cold-formed sections for which design is governed by TI 809-07, "Design of
Load Bearing Cold-Formed Steel Systems and Masonry Veneer / Steel Stud walls".
b. Roofing. Roofing will comply with the requirements of TI 809-29, "Structural
Considerations for Metal Roofing."
c. Certification. American Institute of Steel Construction, Inc. (AISC) certification is
required of all metal building system manufacturers. However, this requirement may be