Common practice for EORs duties over sub-disciplines

[Signious]

Hi Everyone,

This is normally something I would run by my mentor first, but I am kind of curious what your experience is.

I am doing structural for a building where a senior in our shop is the EoR. The client has contracted a roof truss supplier to do design & mfcr of roof trusses. We sign & stamp on the roof layouts as they don't have a senior engineer in shop. When I was peeling through their layouts and shop drawings I had noticed that they did not do a drift load where two different height roofs met. I checked code req's (Canadian NBC 2010) to see what was needed, and drift was required.

Now, I have talked to the roof truss supplier, and they are asking that I provide the load distribution as their software will not come up with an automatic drift load case (They don't know how to do the calculation manually...)

Is this common? I have no problem providing them the loading but something just seems off with these guys just punching numbers into a program without understanding something directly related to their trade.

 

[woodman88]

Welcome to the world of trusses. The seller only has these type of people "with these guys just punching numbers into a program without understanding" and the engineer sealing the truss designs only see the truss design and seal it for what it states only. At least it is this way in the USA.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[msquared48]

Unfortunately, I have to agree with Woodman. This is more common than not.

Mike McCann, PE, SE (WA)

 

[Signious]

Thanks,

I talked to mentor as well, he said pretty much the same thing as you did Woodman. Bill the client an extra hour for consulting services (cost plus), but doesn't make me respect the truss guys any more.

 

[Signious]

Also, I don't think this deserves it's own thread - but it is friggen cool to see. This is a site where the foundation was poured on frozen material about 2 wks ago. After a week or so of temperature in the positives the soil is thawing out and starting to sit down from the frost heave.


Show this to your builders who think heating & hoarding is a money pit.

 

[dcarr82775]

In the US at least the IBC calls for you to specify the drift loads on the drawings as well as C&C wind loads among other things. The truss guy typically misses it unless you catch it during review.

 

[msquared48]

Seen truss systems fail from drift loads. Didn't know that roofs had zippers either. Happens very quickly...

Mike McCann, PE, SE (WA)

 

[TLHS]

The standard of practice in BC as per APEGBC just involves giving structure drift/deflection information and the necessary inputs for them to develop environmental loads (i.e. the code input values) to the specialty engineers, but in in the real world if there's something tricky you should either work out the numbers for them or at least put big letters somewhere telling them to look at the tricky bit so it at least raises red flags. Then when you get their design, verify that they looked at the tricky bit.

 

[dhengr]

I just have it printed in our title block, big letters, where I sign the drawings.... “I’m just the EoR, someone else is responsible for all tricky bits and important stuff.”

 

[woodman88]

dhengr I rather place the statement "I am responsible for only that which I was paid to do. Get the plans approved by the Building Department. Everything else is the owners responsibility." on the plans.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[JStephen]

"The client has contracted a roof truss supplier to do design...they don't have a ...engineer in shop."

There's your problem.

Actually, some of the specifics vary. In some jurisdictions, the rules recognize that you can delegate engineering, and in those cases, whoever it is delegated to, would seal that part of it. You might check into your jurisdiction's rules to see what the specifics are, also if this supplier is licensed to perform engineering in the first place (if that is required), check to make sure your client is paying them for the design (and not just manufacturing), and raise a flag if it isn't getting done. I see situations where Entity A assumes Entity B is responsible for a certain aspect of design, and Entity B assumes Entity A is handling that part of it, and it just doesn't get done. And it sounds like your case is not far from that. You can put notes on the drawings limiting your scope, but I find in real life, they tend to be ignored by pretty much everyone, so that might limit liability in a lawsuit, but doesn't resolve the issue, either.

 

[SrVaro]

Similar to dcarr, I have always shown the drift loads on my drawings. If you all indicating all the other loads way would you not this. Especially if there are architectural features or you are going against an existing structure that they may know about.

Also, I am not sure if I am reading correctly, but I interrupted you stating your firm was sealing the truss drawings completed by the truss supplier. I would never do this as they have their own internal software to design that I doubt they shared with you nor would you have time to learn if they did. It appeared you reviewed something similar to shop drawings including loads, but how are you verifying member sectional?

 

[XR250]

May be slightly off topic, but I typically require that the trusses be designed to require no web bracing if possible.
That is one thing that NEVER gets installed properly (if at all). If it is required, I typically require the webs be sistered rather than by adding horizontal braces. Much easier for them not to screw that up.

 

[TXStructural]

Most manufacturers in the truss industry don't have the staff to determine loads, and I am not sure it is appropriate to expect that. The EOR should probably be specifying ALL loads, since these would be required for the design of supporting structure and foundations. We always did the same for open web bar joist roof systems, and I don't see how wood or light gauge should be different.

We are currently organizing a program about this for my local SEA chapter, since delineation of responsibility is one of the biggest problems on jobs where the EOR only does part of the job.