All Steel Buildings: Non-expandable Building Frames

All Steel Buildings: Non-expandable Bearing Frames

I learn at least one new thing every day. Seemingly whether I try to or not, which makes it ever so much more interesting. I’ve deduced this – when I stop learning, I am dead.

This morning, Eric (one of the owners of Hansen Pole Buildings), asked me, “non-expandable bearing frame – any idea what this means? I’m sure it is something off a steel building quote”.

I told Eric I would have to research further, and once again (thanks to the wonders of the Internet) I quickly had the answer.

This answer came from an all steel building website. A “main frame” is an assemblage of rafters and columns which support the secondary framing members and transfer loads directly to the foundation. An Expandable Frame is designed to support any future building additions with the same width and height which will tie-in to this frame. A Non-Expandable frame is used when X-bracing is not allowed in the endwall. It provides added structural support, compared to the bearing frame. It is also used in Hangar Buildings to support the Header system for the hangar doors in the Endwalls.

While all of this is a mouthful – it did set me to pondering.

My educated guess is, the majority of all steel buildings are designed so as the ends of the buildings cannot be added on to. Or, at least not without major structural considerations.

Post frame (pole buildings) can have their ends added on to relatively easily – however some thought still must be involved.

The easiest – is when the original design incorporates trusses on the endwall which are designed to carry the roof loads from a future “next” bay. In most cases, this takes having a double truss on the endwall which will be later added onto.

There are some things to be looking for when adding to the end of a pole barn.

If the siding is to be removed from the end of the existing building, the adequacy of the roof skin and both endwalls needs to be checked for the ability to carry the shear loads. Not just the new endwall, but also the remaining endwall of the existing building, which is opposite the proposed addition.

Are the existing endwall columns to be removed? This can be tricky – as some buildings are designed with rafters on the endwalls, rather than trusses, or the existing end trusses are not designed to be clearspan, they require the support of the endwall columns.

In any case, the adding to the end of an existing building is best done when involving the assistance and experience of design professionals who can do an analysis on the existing structure, as well as the proposed overall new building. This is the assurance of a result which will perform structurally as desired.


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