Single Span and Multi Span Rigid Frames: What are the Differences?

Blog | October 26th, 2018

Single Span and Multi-Span rigid frames are both recognized as popular structure bracing systems. They both support walls and rooftops. They’re both fabricated in-shop and transported to work sites, where they’re erected and transformed into stylish and functional buildings. The similarities don’t stop there, but we’re looking at the differences between the two structural systems, not the parallels. For openers, Single Span structures create open space.

Single Span Benefits 

Using a rigid steel alloy, a metal that won’t easily deform, the beams and frame pieces stretch across a wide-open area. The internal space contains a massive hall or sports field, a music auditorium or warehouse. As long as the slope of the roof and the structurally rigid capabilities of the steel perform as the fabrication shop intended, the rigid framing holds firm. Walking around this open plan structure, there are no supporting beams, no space-interrupting bracing systems that travel roof-to-floor, and no mandatory room partitioning. This option wasn’t available until structural steel came along. Made from beams of wood, older buildings couldn’t support their own weight without support.

Employing Multi-Span Rigidity 

There are, of course, limitations to the Single Span approach. This framing system uses predetermined roofing slopes and fixed building dimensions. If those architectural parameters are exceeded, the weight of the steel destabilizes the rigid span. So the building must stay relatively small. By introducing a Multi-Span system, multiple roof peaks can march across the length and breadth of a building. There are columns to support the bottom two corners of each triangular frame, and there are rafters and tapered beams to add more strength to the system. More versatile than Single Span, the column and load-bearing walls can support single roof frames or multi-gabled architectures.

A Few Important Drawbacks to Consider 

While dimensional constrictions do hamper Single Span structures, this approach is favoured when small warehouse sheds and athletic facilities require a space-freeing structural solution, one that relies on the rigid and durable properties of hardened steel. For Multi-Span designs, however, there are more materials and more load-bearing factors to plan. Footings increase and foundation-allocated support mechanisms also increase in number. Because of those added system design factors, certain forces can impact this otherwise load-capable design. Ground settling issues, for example, are known to acutely affect Multi-Stage structures.

Again, both structural support systems have their place. Because of the single roofing span, this technique often ends up looking boxy and unattractive. For more profile flexibility, the fabrication shop turns to Multi-Span systems. Still, at least when the building requires plenty of open space, there’s no beating Single Span. If that open area requirement isn’t important, though, it’s easy enough to conceal columns. Just build a few partitioning walls around them.

 

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