TABLE OF CONTENTS This chapter examines a palette of primary structural systems used in pre-engineered buildings. As discussed in the previous chapter, a complex process of choosing a framing system involves much more than structural considerations. Assuming that a metal building system is selected for the project at hand, the next milestone is choosing among the available types of pre-engineered primary framing. Proper selection of primary framing, the backbone of metal buildings, goes a long way toward a successful implementation of the design steps to follow. Some of the factors that influence the choice of main framing include:
Dimensions of the building: width, length, and height
Roof slope
Required column-free clear spans
Occupancy of the building and acceptability of exposed steel columns
Proposed roof and wall materials
After all these factors are considered, the most suitable type of primary framing system frequently becomes obvious.
Manufacturers call their framing systems many different names, often distilled into an alphabet soup of abbreviations. Still, only five basic types of metal building framing are currently on the market:
Tapered beam
Single-span rigid frame
Multispan rigid frame
Single-span and continuous trusses
Lean-to
Each type can be supplied with either single or double roof slope. The most common primary frame systems are shown in Fig. 4.1. Primary framing is normally made either from high-strength steel conforming to ASTM A 992 with a minimum yield strength of 50,000 psi or, now rarely, from ASTM...
