I've designed a traditional timber frame with an English Tie Beam truss for a commercial space. My dilema is that I'm working with an engineer who is adamant that no more than %25 of the crossectional area of the timber is removed at any point in any component.
What was initially intended to be a traditional timber frame is quickly becoming a post and beam.
I'm looking for some references that could lend a different take other than this %25 rule of thumb, so some of the craft could be saved in this frame.

Thanks,

Ian

How wide is the truss? Can you shed some detail of specific joinery which is offensive?

Hi Ian,

There must be hundreds of thousands of English tying joint frames in existence even today and so that means that this system should be capable of passing a structural test.

One must recognise that even the best systems in the world will in fail in due course and so its important (for future generations) that your frame design is capable of coping with both joint failures and component losses so the 25% max section reduction limitation on an individual component might well be a red herring since this does not appear to be tied to service condition. It's fairly easy to check and demonstrate whether your design will work or not especially if this is done using 2D plane frame or 3D Space frame analysis programmes. There are still some unknown unknowns regarding timber design and so designs adopted should ideally be conservative and follow or be based upon or be a development upon other proven timber frame designs.

I suggest that you find yourself an engineer both familiar with and experienced in undertaking the basic structural design checks required when adopting an all wood design.

Regards

Ken Hume P.Eng.

We've dealt with this engineering firm before and the joinery has always passed. The problem is this is a commercial space and they have made %25 the max. crossectional area that can be removed. It's not just one joint in question. It's every component at every point in the frame. It's even gotten to the point where they are not allowing pegs in some joints because of this %25 they are adamant about.
The joinery is very typical really. We haven't reinvented the wheel.
I guess I'm just looking for some literature that I can refer to the next time I go into a meeting with the engineers and stakeholders so this frame isn't completely stripped down
Ian

Seems it shouldn't be about a blanket rule, but studying each piece and joinery decision to see how they are affected by loading.

Have you taken a look at the engineering report put out by the TFG engineering council? Might be a great place to start. Think it is available to members on the TFG website.

Ian

"The problem is this is a commercial space and they have made %25 the max. crossectional area that can be removed. It's not just one joint in question. It's every component at every point in the frame. It's even gotten to the point where they are not allowing pegs in some joints because of this %25 they are adamant about."

Strict adherence to this standard would eliminate tenoned ends, so is there a governing rule to tenon size?

Is this a specialist engineer you hired to engineer the timber frame or the engineer of record who was hired by someone else to engineer the whole building?

We always use our own engineer. We hire him to review and sign and seal our shop drawings and then we submit them to the Engineer of Record, just the same as a conventional wood truss company or a structural steel company. The EOR reviews our signed and sealed shop drawings and sometimes asks for our guy's calculations.

By only using our guy we retain some measure of control. The EOR his happy because he doesn't have to dig too deeply into something he is clueless about. They usually have a couple of questions, but nothing changes from the design and detailing that I worked out with my engineer (with the exception of aesthetic detailing if the architect has an issue).


I suggest you find an engineer who is active in the Timber Frame Engineering Council and begin working with them. No point in trying to teach an engineer his job. Her'es a place to start http://timberframe.org/timber-frame-engineer.html


But if you're in too deep already on this one, the only document I know of that will hold water is the TFEC standards, available through the guild here: http://tfguild.stores.yahoo.net/stfordeoftif.html

Thanks to everyone for their help. This experience has made me want to go for an P.Eng degree.....but then I wouldn't be a timber framer. (Hands flayling in the air)

Hi WoodUjoin,

It's not impossible to be both and given the content of this topic it certainly appears that it would be helpful to the timber framing industry if more employers or associations were supportive of the idea of producing their own P.E / P.Eng. / C.Eng.'s to serve the wood construction industries.

Regards

Ken Hume