Calculation submissions

[gwynn]

Just a random question after seeing a comment in another thread about examining submitted calculations. How often do you actually detail and submit your calculations as part of the design package?

I see this come up fairly often, but rarely experience it myself. Other than a few government departments, asking for calculations is well outside the standard in my experience.

This is especially true for construction engineering work. As both a designer and reviewer of falsework and shoring systems (among other things), the general concensus here seems to be that if you can't figure out how it works without seeing the calculations, you shouldn't be reviewing it. Sentiment seems to run along the lines of "We are being paid to design this, not teach you how to design it." We do not ask for, or expect to receive, calcuations from construction engineers.

 

[Ron]

Most of the analytical work that I do is either delegated design work or forensic. In both cases, I usually have to submit calculations for review. For the delegated design work, the review is usually by the SEOR and/or the Building Department. For the forensic work, it is for review by the opposing parties (usually a tougher crowd!...since their job is to try to prove you're wrong!)

For delegated design work, the calculations are often necessary to show that the design is responsive to the intent of the structural engineers's overall design. I have no problem with that, whatsoever. When calculations are submitted to a building department, it is not done for review but for administrative purposes (to "complete" a file), since they usually do not have staff with adequate knowledge and qualifications for critical review of the calculations.

I have seen delegate engineers refuse to provide calculations...unfortunately in my state,that is against the law if they were requested by the SEOR for review.

For original design work by the SEOR, calculations are almost never submitted to anyone. Most design structural engineers that I deal with consider that an affront to their integrity.

 

[Maury]

I have done a lot of subdivision design, and we are usually required to submit calculations for the storm sewer and storm water detention design. These calculations are almost always reviewed in detail by the city engineering staff.

 

[zelgar]

Calculations should be provided as they're part of the engineering design.

There's a lot of problems that can be eliminated if calculations are provided. It allow the reviewing engineer to clearly understand what the designing engineer was thinking and what assumptions were made with the design.

Even if you've provided calculations doesn't mean they're right. I've reviewed a significant number of calculations performed by PE and have seen a lot of common mistakes (e.g., wrong formula, converting units, misread drawings).

When you provide calculations; make certain they're legible. Provide formulae used, units, references used, etc. Don't just give Sigma= 23*687/57 = 90065, do it right. If you're the only one who has to deal with the calculations, fine; but if you're providing them for others, do it the right way.

This isn't because the reviewer needs to be taught how to design, it's simply to facilitate the review of the material. If as a designer you wish to intentionally delay your project from being reviewd, send us garbage. If you want to facilitate the review, give us a proper design with detailed drawings and calculations.

 

[Ron]

zelgar...I agree with you if an engineer is going to be reviewing the submittal. Many plans examiners are not engineers nor are they required to be. In that context, submitting calculations is a waste of time.

 

[beej67]

In the southeast, hydraulics and hydrology require extensive calculations that must be submit for review and approval.

That's not to say they're always reviewed properly.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[JedClampett]

I request calculations for shoring submittals and always review them, even if they are sealed by others. However, I give the submitting engineer a lot of leeway in his approach.
The reason we require them is that if a disaster happens, we realize we're on the hook just as much as the vendor's engineer. Using shoring as an example, we want to display due diligence with regards to the work by others. With the calculations we can verify that the soil properties seem reasonable, all statics are satisfied, etc. I could perform my own calculations, but if I come up with some results that are just a little off, the vendor’s calculations can indicate whether it is a serious issue or just a different approach.

 

[zdas04]

I recognize that this is a Structural/Civil discussion, but since you put it in Business Practices I thought I'd participate. I always do my calculations in MathCAD. MathCAD has some rudimentary formatting abilities, so it is trivial to print them off and include them in the design. Some of my clients just skip them and never check (but it does kind of add to my credibility). Others review them line by line. I did one last month for a company that NEVER reviews the calcs, but this time they did and found that I had fat fingered a dimension. The error didn't change the recommendation (just reduced a safety factor slightly), but it was useful to support communication.

I don't think there ever is a downside to including the calcs (and anyone who get upset about it is probably trying to hide something). If you use a black-box program that doesn't give you that option then you should print out the input screens and make certain that you have clearly identified the program (and version) you're using and any options you've turned on.

David

 

[hawkaz]

Submitting calculations is standard for most of the United States- especially on the west coast.

I did a project recently where an engineer from England was involved in the initial design, and we were to take the job to fruition. When we asked for his calcs, he didn't know how to respond.

I agree with Zelgar- Don't use "magic" numbers. If you set up your calcualtions properly, they can be used for training purposes for new engineers also.

 

[rcw retired EE]

Electrical & control calculations are very useful for the end user of the facility. For example, when a breaker trips or a tank level control causes problems, a maintenance engineer can use the calculations to help determine if the trip setting was too tight or there is an actual problem.

 

[rowingengineer]

I once submitted calculations that were for the wrong project, no-one noticed or cared when I pointed it out after the building had been complete and we were doing a final filling. These calcs were submitted to the SEOR, After this event I haven’t really felt the need to send too much time making the calcs very clear.

ANY FOOL CAN DESIGN A STRUCTURE. IT TAKES AN ENGINEER TO DESIGN A CONNECTION.”

 

[csd72]

Personally, I always think that to do a good and proper check of a design it should be done without the aid of the original calculations.

My reason for this is that if the original engineer made a logical error that seemed to make sense to them then there is always the chance that it may also seem to make sense to you. I call this error contagion.

Having the calculations is useful, however as if you cannot understand their assumptions on something then it may be necessary to read the appropriate section. But I still think it should be checked independently before that.

 

[beej67]

I once submitted calculations that were for the wrong project, no-one noticed or cared when I pointed it out after the building had been complete and we were doing a final filling.

Well if we've transitioned into the "regulatory horror stories" portion of the thread, I've got some pretty good ones.

I've done site hydrology studies in XP-SWMM before, who's raw data printouts are truly horrific and basically worthless. One of the fundamental flaws with that program. So when using XP-SWMM I used to build my own hydrographs and diagrams of the model to display to reviewers, by exporting to Excel. Quite a time sink.

So we submitted one report once, for a very complicated system, that had all the important hydrographs and data shown, and had the design assumptions and results tabulated nicely. Report was about 8 pages of body, and 20 pages of hand-built maps and results. We get our comments back from the reviewer and they say, "please provide all routings." So on resubmittal, we turned back around and printed 120 pages of fine text time series dyanamic flow calculations out of XP-SWMM, just a wall of numbers really, and handed them a big giant 3 ring binder. The reviewer picked it up, weighed it, said "yeah, this is about right" and approved the design.



Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[csd72]

beej67,

hillarious. Yes drainage calculations are a classic as each local authority can potentially ask for different criteria. In the end it is all statistical jiggery pokery which may/may not be similar to reality.

I can remember one local authority in Australia that required all their drainage calculations in their region done by a very specific program that was only available to buy from their website. I think also that the head drainage engineer was the author - no conflict of interest there!

 

[cry22]

CSD
I just wonder, how do you check your own internal junior engineers? do you do all the calculations all over again? or do you get their calcs? it would be a waste of your time to actually perform the calcs, wouldn't it?

When I review HVAC calcs, I can spot errors just by going thru the output from the computer program checking the benchmarks (CFm/SF; SF/Ton, static pressure calcs, etc..), it rings a bell right away.

Europeans consider claculations as Intelectual property. Gate keepers spin in place in my opinion, we are talking about calculations for the construction industry which have been around forever, not exactly rocket science.

 

[gwynn]

Cry

I know you were asking csd, but our in house checks vary. For smaller or simple projects, the calculations are handed over and reviewed. For larger projects it is done as an independent review. The checker gets the design drawings or analysis report and that is it.

 

[Ron]

The calcs I review are usually structural, geotechnical, pavements or vapor transport. I do benchmark sampling of the calcs, such as for wind loads, I will check a couple of coefficients as if I were doing the calcs myself.

After doing calculation and other review for many years, you get a sense of what to look for and how to do so efficiently.

 

[rowingengineer]

I have a few rules of thumb I like to use.

ANY FOOL CAN DESIGN A STRUCTURE. IT TAKES AN ENGINEER TO DESIGN A CONNECTION.”

 

[vthomidis]

.....lesson learned through my 17 year experience :

the more detailed and multipage calculations you provide - the less probability anybody actually checking any of them..