Specialty engineered items, calculations and submittal review

[Dennis59]

A question for consulting engineers and specialty design engineers:

A magazine article from November 2000

http://www.csemag.com/magazine/articles/c00k021.asp

talked about calculations for specialty engineer-designed items, and how these calculations should be handled by the consultant during the submittal review process. I never saw a follow-up to this article, but I think one is warranted.

Structural examples: wood trusses, cold-formed steel trusses, structural precast concrete, geodesic domes, bridge cranes, etc.
Non-structural examples: fire protection, lightening protection, etc.
Partially-structural examples: wastewater clarifiers, equipment stands, etc.

The consulting engineering firms I have worked for have generally asked for calculations to be submitted along with PE-certified drawings. Once I receive these calculations, I look for the place where the design engineer states his/her design criteria, and I make sure that it matches what I've specified.

My question is: what is the "right thing" to do next? I have heard several approaches over the years:

1) Stop there; your only obligation is to make sure that calculations/drawings are PE-certified and that they claim to have followed your specified criteria.
2) Dig a little deeper and see if the rest of the submittal makes sense - e.g. look for the pages of calculations that are applicable to some of the more critical items and make sure that the specialty engineer's calculations agree with the vendor's drawings.
3) Review everything - calculations and drawings - as if you personally are responsible for the design.
4) Don't even ask for the calculations; you're just opening the door to a lawsuit if something isn't designed right (the thought here, apparently, is that if you don't look at them you can't be held liable).


Let me give you another example:

http://www.geocities.com/SiliconValley/Hub/5968/pnewsletter.htm#b1299

As I understand this December 1999 newsletter article, someone determined that calculations for wood trusses didn't appear to be correct. After further digging, it was alleged that the specialty engineer PE who was signing off on the design wasn't actually doing what I would consider 'truss design'.

My own personal experience is that more than once I have looked at PE-certified precast and wood truss submittal packages and had to send them back because of one or more of the following:
*calculations and drawings didn't agree
*calculation summary sheet said my criteria was followed, but within the calculations it wasn't really being used
*calculations had errors that were significant enough to cause member size(s) to be changed on the resubmittal


So I am wondering - what, if anything, is the "standard practice of the industry" when it comes to handling a specialty engineer submittal?

More specifically, what is your own personal opinion, and does your opinion agree with that of the firm you work for (if applicable)?

Is this something that may vary from state to state?

Thank you for any response you care to offer.

 

[Ron]

Here in Florida, this is known as "delegated engineering". In this process, the structural engineer of record is required to provide the delegated engineer (specialty engineering) with the criteria of design, and the delegated engineer is to provide by the criteria and code. The structural engineer of record is responsible for verification of the delegated engineer's response to the stated criteria.

 

[Lutfi]

I ask specialty engineers to submit calculations. Hand cal calculations are easy to follow as long as they are clear. I require that computer output and input should include software description, and explanation of the input and output.

Regards,


Lutfi

http://www.cdeco.com

 

[UcfSE]

I've been doing specialty engineering for light gauge studs, curtain walls and such, for several months now. When I get a new job, I read the spec section for requirements as well as the architectural and structural notes and follow these for wind pressures, deflection requirements and any other cirteria and design in accordance with the AISI code. I submit my package with a section for drawings, and the calculations and appendices to the calcs showing all the member and connection engineering that I do for the job. It seems to be working since I haven't had any thing returned or had problems with my submittals (knock on wood). I try to keep in mind all the things I didn't like about other shop drawings and calcs I reviewed and correct that for my own submittals.

When I receive shop drawings that we require signed and sealed engineering, I review the engineering for general correctness and compliance with our requirements and leave it at that. I spot check some things and look for anything that raises a red flag so to speak. The only thing I've ever had a problem with is pre-engineered truss packages. The majority of this was with the truss engineer not using the correct loads. I've sent many back because they used the wrong wind speed, exposure, category, enclosure or some combination of those.

 

[BFPartners]

When we submit the calculations to the client, we are of the assumption that the calculations will be passed on to the next firm performing work on the item. Second, this is a reassurance to the client we didn't accept his work and not perform any calcualtions, that is, a due dillagence has been performed. Remember, if you are an engineer of any discipline and you have asked for the design notes, you then have the responsibilty to review the work in partial or in whole. We have been previously "stung" in these types of situations and the "I didn't know" doesn't cut it!!!

 

[JStephen]

I'm in the specialty design category. I would suggest that you omit asking for the calculations and do request that the drawings themselves show the load criteria and whatever else you need to have shown.

The intent of the specialty design system is that the specialty design engineer has knowledge and experience in that particular product that the engineer-of-record doesn't have. If the engineer-of-record is fully knowledgable in the areas of interest, then there's no reason to have two engineers involved- just fully detail the stuff on the contract drawings and build it off that. (Or, request shop drawings, but don't require PE certification- although state laws vary as to how that works.) And if the engineer-of-record isn't too knowledgable in those areas, then there's not a whole lot of reason to go nitpicking in the calculations.

I have learned the hard way, that the more you submit in the way of calculations, the more criticisms you get on it from unknowledgable engineers. So when calculations are requested, I usually prepare a set showing the bare minimum of information that the customer might expect, and perhaps two thirds of the calculations that are done are never seen by the customer. And of course, in most cases, the customers don't realize that there is anything else that should be done, and everyone is happy.

One thing I have learned in the past is that there is literally no end to the calculations that can be generated for any particular product. A part of the engineering experience that goes into the design involves knowing what does and what does not need any calculations to be done.

And FYI, probably 80% or more of our customers do not request calculations.

I notice that you mention geodesic domes. To me, that is an application that calls for structural design software to be used. However, I have been noticing that in recent years, when the dome people submit calculations, they tend to be very basic- using MC/I to find wind moment distribution to the support points for example. I suspect that they DO use structural design software in-house, then generate a simpler set of calcs to give to consultants.

 

[JStephen]

Some additional thoughts-
Do you normally require calculations to be submitted if you subcontract engineering services? Or do you normally submit calculations to the owner for review for your work?

For example, if you as the engineer-of-record hire a geotech or electrical engineer, do you expect to see calculations from those people for their work?

On the issue of finding errors in work done- I don't know that submitting calculations is the answer there. That's good that you found those errors. On the other hand, you might could have spent that time rechecking your own work, and found errors there. And after you double check it, you could probably triple-check it and find the occasional goof. And goodness knows, that the contract drawings we get in here have plenty of errors and inconsistencies on them, so this is not something limited to contractors. I've seen jobs where it was obvious that the person that wrote the specs and the person that drew the drawings had never talked to each other- and have a contract in hand right now that is like that, in fact. We actually quoted it both ways- "per plans" and "per specs"- at two different prices.

And...what to do about spreadsheets? They don't conveniently show all the calculations (IE, the formulas). Yet, they're not "canned" where you have some reasonable assurance that the calculation contained is correct.

 

[Dennis59]

There are really a couple of different issues here, I think.

1) Is there really an 'industry standard' approach to the extent of review a consultant should perform on a specialty engineer-designed submittal, and if so, what is it?

2) Is it good/right to require specialty engineers to submit calculations in the first place?

The main reason for my original post was issue #1. I would still appreciate any more answers from the readers of this forum.

As far as #2, I have some thoughts that I'll run up the flagpole - y'all can shoot them down if you want. I'm using precast hollow core planks as an example, but the same could be done with wood trusses, a fire protection system, or some other specialty engineer item:

I ~could~ design precast concrete hollowcore planks and show the hole sizes and strand patterns on my structural design drawings, but that would be defeating the entire purpose of the precast hollow core slab industry. They've got a specialized product that differs from one vendor to the next, and only if I let THEM do the design will the Owner benefit with a lower cost well-performing building. BUT, I personally think that the specialty design engineer that does precast plank design for a living should do a better job of it than someone who does CMU one day, structural steel the next day, concrete the day after that and so on. I can't possibly be as competitive design-wise as someone who does it most every day. I don't have the day-to-day experience, and I don't have the specialty software.
So I think it also follows that I should be able to expect perhaps a higher level of calculation 'quality' from that specialty engineer. I'm not going to argue with the legitimate shortcuts that he/she has learned, but I do think that there should be something in those calculations that specifically acknowledges the design criteria, and specifically addresses the more intricate elements of the design. Say there are a thousand planks on a job. Maybe only 5 or 6 of them will be anything out of the ordinary. Those are the ones I am tempted to look at a little more carefully and see if the PE-certified shop drawing makes sense.
But if I receive a submittal package that shows a fairly light strand pattern for a plank that obviously has more load on it and/or more cutouts than the others, is it wrong for me to want to look at the corresponding calculations and see if it looks like everything was addressed properly?


Wood truss engineers have wood truss software. I don't (and I don't think I should have to). I'm not going to question the software, but if I look at two essentially identical trusses from two essentially identical corners of the building and see that their member sizes are different what should I do? What I did was to look at the loads they applied and found that loads to one truss were significantly less than the other. Is this going too far?

My mention of geodesic domes was based on a recent experience. In a northern state, I was covering a circular tank that was tucked in next to a taller building. This necessitated that a snow drift load be specified. The first submittal package had no snow drift load applied, however. Only by digging into their calculations was I able to determine thins.

I would say that maybe I am the only one who has occasional problems with this, but based on UcfSE' response, maybe I am not.

 

[JAE]

I brought up a similar subject regarding the general purpose, use and dispersal of calculations - here:
thread507-89434

But that dealt with the EOR's calculations and I think this topic is a little different in that it is the EOR asking for some assurance that the delegated design work has been properly done.

In a nutshell, the legal requirement is for the EOR to ensure the safety and welfare of the public. How you go about that is up to you but you will be judged (if something goes wrong) based on what A REASONABLE ENGINEER IN THE INDUSTRY WOULD DO. And this is exactly your question - what is the standard of practice by which I'll be judged.

I would think that most engineers would insist, at least, on:

1. Some declaration by the delegated engineer of the design loads and parameters used (to compare with those required by your design documents).

2. Some assurance that the delegated engineer and specialty entity has qualifications to design and fabricate the delegated entity.

3. Some review of any unique, or difficult features of the specialty design - for instance, a steel joist is a specialty design delegated to others...however, they are fairly simple, quite standardized, and the massive use of these things provides lots of assurance. But a unique "thing" such as a geodesic dome, not done everyday, would draw more attention by me to its details and features.

So it does boil down to your decision and judgement, as the EOR, as to how deep you go into it to ensure the public safety.

 

[JStephen]

Dennis, I think your examples point out some of the difficulties involved in submitting "calculations".

It sounds like in the case of the wood truss, you never see the actual calculations- just the computer printout. In the case of the geodesic dome, I doubt you ever saw the actual design calculations- but either a computer printout of results, or a set of simplistic calculations that aren't necessarily used for actual dome design. In both these cases, what you actually needed, and what you wound up reviewing, were the loads applied to the structures, not the calculations themselves. And that information can and should be shown on the drawings in some way.

In all three cases, the quickest and simplest way to resolve the issues is to pick up the phone, call the engineer in question, and ask about why this doesn't jive with that, etc.

As far as the requirement to submit calculations- I find that is embedded in standard specifications; it seems never to be based on a particular engineer's judgement, but rather on whether that consulting company's standard specification has that requirement in that technical section.

 

[UcfSE]

Some more info, we don't normally submit calcs on projects for which we are the EOR unless they are required by the local building official. Typically on projects in south FL for instance we have to submit calcs with drawings to the building department. When doing specialty engineering, most of the time either the structural notes page or the building specs require calculations with specialty engineering submittals. To me that takes the guess work out of whether you submit calcs. My submittals include a page of notes stating what design loads I used, any deflection criteria, fastener information, etc. and some explanation of software output so that someone not familliar with the program can reasonably understand at what he/she is looking.