There are several types of purlins that are used in steel building systems. Some of these are rather similar; some are a bit different. It’s important to understand the difference between them in designing your building. Rather than delineating all of the major (and minor) types, we will just focus on the two most common. Look over the following information and see what will work best for your project.

Implemented in any number of plans is a purlin-style of hot-rolled steel beams. All-steel structures came into general use many years after the inception of hot-rolled steel purlins. Rooftop framing technology for manufacturing use in the early 1900’s incorporated the roof trusses being spanned with hot-rolled channel and I-beam purlins. This approach can still be used in pre-engineered steel buildings today, especially in production facilities needing substantial interior support. The selection of hot-rolled steel beams is part and parcel of their excellent load-carrying abilities as matched up to decreased gauge designs. Spans 30-feet and above can employ the hot-rolled steel beams. And these are also supportive of ample overhead loads in the building interior. This application can be very expensive even though it is substantial.

“C” and “Z” cold-formed structural frameworks are not readily customizable for uplift, however, unbraced or braced hot-rolled steel purlins are easily customized for this. Hot-rolled steel structure roof purlins’ symmetry is contingent on engineered channels and wide flanges. Steel decking which enables excellent reinforcement and can go across long distances can be utilized with hot-rolled purlins. It is ordinarily quite economical to place these over the primary frame rafters. The given load bearing efficiency of the deck determines the purlins’ intervals. Preparing for the energy acting on the purlins can be accomplished by installing a roof-deck diaphragm or sag rod bracing. There can be attachment of sag rods up to three inches below the topmost part of the steel. This aids in lowering torsional characteristics.

Utilizing open-web steel joists is a second purlin configuration to think about. Pre-engineered steel structure systems that are above 30-feet in span along with buildings requiring expansive bays should benefit from open web joists. These are also called bar joists and can span larger areas than hot-rolled or cold-formed purlins.

Bar joists, in comparison, have an inability to withstand major twisting or turning energies as they lack solid webs to assist in dispensing of this stress. A standing-seam roof can be readily attached and the diaphragm capability furnished by horizontal rod or cable bracing within pre-fabricated, pre-engineered steel structures using open-web joists.

To reinforce standing-seam roofing there are two proven approaches in efficient set-up methods featuring bar joists. One plan is to affix thin gauge hat channels atop the steel deck, vertical to its flutes and its particular steel deck. Another plan is to not use the steel deck in the configuration, but rather install compactly spaced cross bridging in its place. Such cross bridging along the close spacing allows soundness with the entire assembly, and to deter any dynamics that may be acting.

Well, what do you think Certainly you must be glad that we didn’t talk about all the purlin types. But, we do hope that what we did cover is instrumental in the planning stages of your building project. Or, at least we hope it’s educational in understanding the terms you encounter when involved in a steel building project.