TABLE OF CONTENTS In this chapter we review the structural basics of metal building systems. We begin with a brief discussion of the structural loads (or loads, for simplicity) that the systems typically must carry, the methods of combining these loads, and the methods of analysis. We then discuss how metal building systems work structurally and what their competition is, and examine the process of system selection. Our goal is to show how and when to make an informed judgment about suitability of pre-engineered framing for a particular project.
Dead load is the weight of all permanent construction materials, such as roofing, framing, and other structural elements. Being well defined and known in advance, dead load is assigned a relatively low factor of safety in the ultimate (load factor) design.
Collateral or superimposed dead load is a specific type of dead load that includes the weight of any materials other than the permanent construction. It may account for the weight of mechanical ducts, pipes, sprinklers, electrical work, future ceilings, and reroofing.
How much do these components weigh? The MBMA Manual1 suggests the following typical values:
Ceilings: 1 to 3 psf
Lighting: 0.1 to 1 psf
Heating, ventilating, air conditioning (HVAC) ducts (office/commercial occupancy): 1 psf
Sprinklers: 1.5 psf for dry systems, 3 psf for wet systems
Adding up the numbers, a commercial or industrial building with sprinklers, lights, and mechanical ducts but without ceiling could be designed for the collateral...
