Professional Obligation

[jike]

What professional obligation do I have when I have noticed that a structure was not designed for drifted snow? I have called the design engineer and he agrees and has looked at the situation.

I have done some calcs and believe the metal roof deck is 30% overstressed with a 3 span cont. condition. The joist nearest the wall is about 20 % overstressed. This includes a revaluation of all existing dead loads since they were originally overestimated.

The design engineer says that he looked at it and he thinks he can justify saying that it is OK.

Do I leave it here, since this is his responsibility, or do I talk to him again and try to convince him that it is more overstressed than he thinks?

Do I have any obligation to inform the Owner or local building department?

 

[RDK]

What you are really doing is questioning the competence of a fellow engineer.

Here in Manitoba our local association’s rules are clear on this. The correct forum is to inform the Investigations Committee of the association and allow them to investigate the issue. If necessary they can and will inform the appropriate authorities and the owner.

A full complaint would include your calculations and other observations.

You may of course have one final discussion with the designer in an effort to get him to take some action.

At the end of the day, your first professional obligation is to protect the public.




Rick Kitson MBA P.Eng

Construction Project Management
From conception to completion

http://www.kitsonengineering.com

 

[JAE]

Your obligation is to protect the public welfare first and foremost.

That said, check with your state's engineering laws and code of conduct. If you are not a PE, then find another PE to review them for guidance. Some states in the US require an engineer to notify the owner direct if they know or are aware of a potential conflict.

In any case, document whatever you do and say.

The decking being overstressed wouldn't bother me all that much as it would still tend to react as a tension element between joists (like a cantenary curve).

The joists being 20% overstressed means that they will not fall down in a code snow load, but the required safety factor is not present. Therefore, if perchance a larger than code snow load would occur, you might have joists going plastic on you and failure is a potential.

Probably, as the snow built up, the joists would excessively sag, giving some warning that there is a problem. I've seen a couple of buildings where this has occurred - lots of distress in the hung acoustical ceiling but no failure - even with 8 foot of snow - way over the design. How the joists managed to stay intact was beyond me.

Was the 20% overstress in flexure or shear? Again, flexure offers the potential warning while shear might involve a diagonal weld connection failing.

 

[Bbird]

jike,

There is problem in here as your description seems to suggest the investigation is personal, incidental and you have no formal obligation to check the design calculation.

The building has not failed or showed any sign of distress. Nevertheless as an experienced engineer you believe some structural members may have been undersized. You therefore brought this to the designer's attention.

The designer verbally confirmed to you that in his opinion his design could be justified.

The only real leverage you have is to challenge the relevant design code has not been complied with. If you feel strongly about it you can seek clarification (say ask to see the design calculation to compare with your assessment) from the designer, before bring the matter to the authority. From the description of others there is a possibility of a reduction in the safety factors but there is no imminent risk of a collapse. Thus it may be premature to disturb the owner because the designer may be willing to do something about it.

If the designer fails to convince you then you have an obligation to alert to the authority formally by pointing out the design deficiency. If you feel the property can suffer distortion, damage or risk to its occupants then you have a moral duty as well as professional obligation to let the owner aware of your view.

I think the designer has a right to demonstrate to you that his design could be satisfactory, say by bringing in considerations additional to a standard design like different methods of analysis and 3D effects etc.