I have a potential client who is looking into building a 70ft wide free-span timberframe shop with about an 8/12 +/- pitch saltbox roof. ??? :o (That's what I thought!!)
What is the widest building width that a hammer beam truss can appropriately span?
Or has anyone built a timberfame girder truss to span long widths?
Looking for options and direction, ..."no need to re-invent the wheel"
Rooster
This is definitely one for the engineers. Wrangling the assymetrical forces of a saltbox roof under a single truss will be quite a challenge, have you got a sketch?
I've seen hammer beams spanning ~60ft and suspect some cathedrals go even wider, but these are buttressed structures. A scissors truss might be another option.
As for the TF girder, I haven't done it but it's essentially the same problem as a bridge.
The Guelph bridge (a 1992 guild project) is 120' clear span.
I would say the possible client does not understand the hammer beam "truss". Is this their idea? Did it come from a glossy magazine? Buttress indeed.
If the building is 70' wide how long is it?
I have an engineer now looking at a 36' queen rod truss for my next possible up coming job.
Tim
Thanks guys,
I haven't received a sketch yet, but I do know that the building is divided up into two halves...one end is a 42ft wide x 56ft gambrel roof style, two story draft horse barn, which also has 14ft x 56ft lean-to additions attached to each side.
42 +14+14=70ft
The other end of the building is the 70ft x100ft free span, saltbox style roof, timberframe farm and mechanics/ maintenence shop.
70ft x 156ft total footprint.
He likes the look of old timber and is asking that it be made out of used barn material. I have built a 51ft Multiple Kingpost truss covered bridge, so I feel more comfotable with that sort of system. I also looked at some of the Guild's truss literature and found a couple of Queen/King truss combinations that would work for a shorter span. We are still in the early stages of planning, and I have a couple of alternatives/compromises to propose if needed.
Tim,
30-36ft Queen trusses with hanging support rods are very common in Wisconsin Dairy barns built between c.1890-1920. Let me know if you want to pick my brain on that one.
Rooster
I been in some churches with large span hammer truss design. The walls are mortared stone with a substantial buttress, also of stone, to support the outward thrust of each truss.
I think you will also have to consider a heavy snow load..........