Calculations: Personal Tool or Public Record 9

[JAE]

Here is a qustion for the ages.

Structural engineers provide professional services to their clients. These services involve taking specialized knowledge of material behaviors and applying them in such a way as to "turn ideas into reality."

The process in getting an idea put together that is strong enough, stiff enough, ductile enough, etc. and meets the required building codes involves the engineer using various tools. Traditionally, these tools have involved pencils, paper, calculators, slide rules, etc. Lately, computers and the internet have taken hold. All of these are simply tools that allow the engineer to apply his/her knowledge and create their true instrument of service - the design.

The way an engineer communicates this design is via drawings. The way the design is developed is via calculations. Calculations, I would suggest, are NOT the service an engineer provides. Calculations are NOT an entity that is sold to a client.

But today, it seems, calculations are required to be part of a "submittal" to cities, agencies, etc. as part of the compilation of services that need to be checked by a reviewer, usually an engineer-type working for the governing agency.

I would appreciate comments from you all out there as to your take on this. Are calculations something that should be "reviewed" or are they my own personal tool that allow me to organize my thoughts, develop my ideas, etc. Can a reviewer say, for example, that I need to format my calcs in a particular fashion? Are they stepping beyond their function to review plans for concurrance with a building code?

I guess my bottom line is that the calcs are a road map that show, perhaps, how I got from idea to design. But they (the calcs) are usually very much open to interpretation, confusion, etc. based on the way the engineer uses them to develop his ideas. Not everyone writes down or calculates things in the same way.

Thoughts on this?

 

[flamby]

I work for a company that provides consultancy services to the clients and also seeks consultancy for specialized item from other International consultants. In the process I have been at both ends of the table and I guess there are many perspectives of the same question you ask depending on who is looking.

1) As a Client I insist on calculations. In one case one steel item was very heavily designed by one consultant of International repute. Upon reviewing the calculations, we saw that while loads and stresses were changed from a previous submission, they did not change the overall sections, so as to save their drafting time. It costs a client a lot to built and he is entitled to see that what has been designed is not under/over designed. This is seen in calculations, not drawings.

2) As a consultant, I find myself in total agreement with you. I have over the years learned some tricks of the trade and intricacies of design. I saw the Dos and Donts
the hard way, by making mistakes and burning the midnight oil. The clients want all of this in just one submission! Even if they get it, how on earth they are going to see it in the light of my experience? Just a recent grad from client's office will tell me, it all is not acceptable and whether I do have any "reference" that this thing was done in past. It all is an endless round of sheer frustration when they start telling me how to do MY work.

Sometimes, I get mad at them and yell, do you ask for calculations when you buy a car? Granting you do, do you hope to get one in your lifetime?

Since, I have played both the roles, I never tell our consultants to use a "Format". Anything, from back of the envelope to paper-napkins to computer output is acceptable.


Regards.

 

[pulshakha]

I totally agree with Flame on his second point and praticularly like the example of buying a car. Although i work for a government agency and as a rule bound to ask for the calculations, but personally it is against my instinct. In case of any suspicion in the design it is very difficult to follow the calculations, particularly if it is done with the computer spreadsheet etc.

The designer is responsible for the calculations and in case of any suspicion the client should ask him to explain or review his work. Forcing the consultant to submit the calculations is not only the waste of paper and time but also against his copyright in some way, i think.

 

[MotorCity]

Here is my 2 cents.

As an engineer, I always welcome suggestions and comments that are intended to benefit the design. That said, drawings and calculations are the products of design and should be subject to review by anybody competent in that area. Any engineer that is confident in his or her work should not have a problem with a peer review. I have seen many engineers become offended when others critique their design, but the client and safety of the public is far more important than one's ego.

Imagine this scenario: a critical error in the design calculations is made by an engineer with 20 years of experience who could perform the calculations in his sleep. This error results in an under-designed member that could fail and result in loss of life. Sounds like a stretch you say?

I was the young engineer out of school for 3 WEEKS that found the error on a bridge design. The biggest mistake you can make is thinking that you won't make one.

 

[DaveAtkins]

"Custom" designed structures, such as buildings and bridges, are typically not subjected to rigorous testing prior to being used. On the other hand, things like automobiles and the medicine we take are subjected to a lot of testing before hitting the market. Being allowed to review calculations is one way for a public official to ensure that buildings and bridges will be safe for the public to use, since they will not be tested. Since licensed design professionals have varying degrees of ability, public officials need the opportunity to assess the design of a particular structure, and one of the ways this is done is through the review of calculations. For example, in my State a registered architect can create and submit structural calculations to the State for review, and on occasion, these calcualtions get rejected, because the architect does not have a strong structural engineering background.

DaveAtkins

 

[JAE]

MotorCity,
I agree with your example of the error, and that any engineer is capable of making errors in design.

But my main points were not dealing with quality assurance within an organization, or how an engineer checks their calcs within their department.

My points were that agencies that ask for calculations do so many times,
a. without the competency available to do anything with them,
b. when they do review them, they many times comment on the format of the calcs and not on the code requirements inherent within them, and
c. Calculations are not inherently reviewable anyway - they are extremely subject to interpretation, and mis-interpretation by people outside the engineer's organization.

 

[SlideRuleEra]

When I worked for a public utility we would would request design calculations only on certain occasions. The best example would be something like this:

During a design review there were concerns about technical details (beam sizing, connection detailing, reinforcing steel placement, etc.) and the design firm's representatives would either gloss over the situation or provide token responses. At this point we would request the calculations, not to perform a detail check, but to use as the basis for intelligent additional questions.

Many times the design firm was correct and we would move on. Other times we might discover that the design was based on automated calculations performed by a very junior individual who had little or no understanding of engineering principals.

A third possibility was rather surprising; an engineer who was quite competent and very experienced in his own field may be tripped up by a lack of knowledge in another discipline. Here is an example:
A well qualifed foundation engineer insisted that that we would need unusually strict requirements on concrete placement temperature for 4 ft diameter, 40 ft long drilled pier caissons in soil with a very high water table. Review of his calculations revealed that he had no concept of heat transfer. On addtional questioning he insisted that the only way that heat could leave the caissons was through the top that was exposed to air. He refused to accept that the entire "cylinder" was immersed in a virtual water bath and would lose significant heat in a radial direction. As the Owner's representative we finally had to direct him to accept less strict concrete placement temperature requirements.
Result: direct cost savings >$50,000 for the project and no problems with the concrete.

 

[redhead]

The BOCA Code requires submittal of signed and sealed calculations as part of the permit application process. This Code is still in force in many localities.The New Jersey Uniform Construction Code, which has adopted the IBC 2000 as the Building Subcode, has the same requirement.

I am unfamiliar with the UBC and SBC, but my guess is that they contain the same provision. Check the administrative section of the Codes.

 

[JAE]

The IBC does not directly identify "calculations" as part of the submittal review process. It does, however, refer to "other data" in section 106.1 as being in addition to the drawings.

 

[rowe]

In my opinion, a well organized set of design calculations should be generated with any significant design project, whether the client requires a copy or not.

The design calcs should enable another engineer to follow the design without undue confusion.

If there are design issues that a long-practicing engineer may be certain are not critical, state that assumption in the design calculation (i.e. "shear strength is OK by inspection").

There are several reasons why documentation of a design project is good. I can't think of any reason why a well organized set of design calcs would not be good.

I know organization of design calculations can take some time. I realize that the client typically is only interested in the set of plans, and that time saved on the design project generates more profit for the design company (for lump sum fees anyway), but with a well organized and complete set of design calculations, the almost inevitable call from the contractor, owner, etc. can be addressed confidently, efficiently, and fully without having to rely on memory (or the design engineer if the design engineer no longer works for the design company).

A well organized set of design calculations can be extremely helpful on future projects that may be similar (sort of a template).

A well organized set of design calculations can be extremely helpful to junior engineers or engrs-in-training. It's easy to backcheck those calcs that are included in the design notes, but how does an unexperienced engineer know what to check if it isn't in the design notes?

 

[JedClampett]

I don't mind giving the calculations to the owner. After all, they paid you to do them. I mildly resent giving the calculations to the plan reviewer. I do, grudgingly, when requested. The plan reviewers usually don't have time to really understand the drawings (some do) and thinking they can get something out of the calculations is really pushing it. I particularly don't like sealing calculations. I feel I'm putting my license at risk even if I make an innocent mistake that doesn't impact the design. If I do a beam calculation and the length changes by 6 inches, it might not impact the design, but the calculation is technically wrong. If the plan reviewer gets a wild hair somewhere he could lodge a complaint. After all, you do have a discrepancy.
I feel that plan reviewers should have enough experience to look at a design and determine whether it meets code. It's not that tough to design something backwards if you're suspicious. Or pick up the phone and ask. Trying to wade through a couple of hundred pages of computer printouts and hand calculations is a poor use of time.

 

[LPPE]

My $0.02 - Building officials, although competent in many areas, are generally not experts in any one particular area. Therefore, most of them probably have no idea what they'd be looking at if you submitted calculations anyway.
Overall, its OK with me if anyone wants to look at my calculations.
If I start getting comments back like "I calculated a uniform load of 137 #/ft, and you used 140 #/ft. Why?" I may have a problem....

 

[JAE]

rowe - I agree that "A good set of design calculations" is a good thing. However, even a good set is still NOT an instrument of your service as an engineer. It is ONLY your tool to perform the calculations. And even a good set of calcs is subject to mis-interpretation by a code official.

JedClampett - I agree with all your comments except your second sentence. I am NOT paid to do calculations. I am paid to provide engineering services to the client. Under all US state licensing laws, if I could somehow design a beam without a calculation (someday maybe possible) then I would still be performing engineering, but not creating any calculations. I know this sounds absurd but my point again is that calcs are MY tool, not an instrument of service that "others" have a right to see.

LPPE - Lack of expertise is evident many times and you're right.

 

[Focht3]

I first encountered this doing a design verification for a very large generator foundation at Kwajalein Atoll about 10 years ago. (Three or four generators supplied electricity for the whole base.) It seemed odd at the time; and it was a real pain. But it gave me an opportunity to 'flag' a few errors in the COE documents that were at odds with the geotechnical data (and good engineering judgment.) The design problem was sufficiently unique that I kept the calculations for future reference.

It was a rush job, took a lot of time, and was moderately expensive. (It was a force contract, so the U.S. Army paid the cost.) The really sad thing is that reportedly no one looked at them at all.

I don't mind someone reviewing my work. I do mind someone demanding calculations so they can check a box on a form...



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[rowe]

I look at it like this:

If the scope of services includes a set of plans and a set of design calculations (like many government entities do), then you've no choice but to supply the calcs. If design calcs are not included in the scope of work and the client does request them, then you can either provide them as complimentary (good politics perhaps) or charge an appropriate fee.

I may be missing the point. I don't think I agree that calculations are solely part of YOUR tools in preparing a design. I would consider the design calculations as legal documentation of the final design. If some question arises concerning the structure, and an independant engineer is called upon to check the design, his conclusions will be based upon calculations. If you have to defend your design, you'll have to base your defense upon calculations.

With regard to misinterpretation, I again may be missing the point. A well organized set of design calculations should be such that another engineer qualified to design the same structure should be able to follow the design calculations.

With regard to Building code officials misinterpreting engineering calcs, I would not expect them to be able to follow the calcs. I would, perhaps, expect them to review the design criteria and recognize the code prescribed loads, which should be a well defined subsection of the design calculations.

By the way, (i don't always practice what i preach).

 

[Ron]

JAE...good thread.

Much of the analysis I do is called "delegated" work from the structural engineer of record. In my resident state, there is a statutory requirement to provide calculations to the structural engineer of record for his review on all delegated work. Delegated work may be the design of structural joints for shop fabrication, design of free-standing "manufactured" structures, and a variety of other applications not directly done by the SER. Likewise, when I am the SER, I require calculations for delegated work as this is a requirement of the SER as well.

I do not feel it necessary for the SER to submit calculations for his design to a public agency. Often the public agency has little or no capability to review the design in an appropriate context and it is reasonable that two engineers may differ in their opinion as to applicable code provisions, methods of analysis, loading configurations and the like. That's called Engineering Judgment for which we have been given statutory authority to exercise as evidenced by signing and sealing a document or plan.

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[JAE]

If a set of good design calculations is a "legal documentation of the final design", rowe, I would have to ask when that fact was ever instituted in the engineering profession. I know it wasn't there in the 50's, 60's or 70's.

I don't really disagree with you on much here, just that my early training at the feet of engineers who started in the business in 1927 through 1960 all rarely, if ever, allowed anyone to see their calculations. It wasn't that the calcs were bad (they weren't) or that they were trying to hide something, but that they felt it was an affront to their professionalism, as well as their reputation and respect due to a professional.

The comparison could be made with doctors, lawyers, etc. who make all kinds of decisions in their professions through processes that many times COULD be written down but aren't. I can't ever remember seeing or hearing of a patient asking a doctor to verify his decision via calculations why he/she prescribed 50 mg of a a drug instead of 100 mg. Its his or her profession of the science in which they were trained. Not a mechanical process of following a set standard calculation.

I guess my ramblings here have to do with my dismay at the de-professionalizing of the engineering profession. We are nowadays not called upon to develop (or profess) our skills in developing a design, we are asked to show, step by step, the exact numerical bread crumb trail that got us to say, "Voila! its a W12x26!". While engineering does tend toward the process, I think we are forgetting the "profess" part of it all.

We diminish ourselves by stooping and bowing before our great kings (the reviewers) and humbly handing them our scribblings in the hope that they will be generous and, with wisdom, crown us with the glory of that most noble stamp: "PERMIT APPROVED".

If this then is our profession, then delivery boys are Communication Engineers.

 

[flamby]

I agree that calculations are needed and I do them in detail. But the submittal is, sometimes, a censored version.

I will not be so forthcoming to spell out each and every step of the design process. The reasons are:-

1. The clients are fussy and will ask you to prove every word you divulge. An inconvenience to me.

2. There are codes. When did you realize that codes are clearly understood, have no ambiguities and need no further commentaries? I am resentful towards these code-socities who tell you to mutiply X with Y, without giving any reason, Do they take engineers as mathematically/ technically dumb?

3. You will be required to educate them the whole process of design. Where is the time?

Nevertheless, I WILL submit calculations. Just bare minimum, as per code, very elementary so that a donkey can understand them.

Generally, not the volume of submission, but time taken for approval is the main problem. I realize the importance of calculations but if the client can be satisfied with just STAAD crap, why give more?

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[Taro]

Good topic, JAE. I agree that calculations are not an integral part of our instruments of service.

Some of the previous posts seem to be addressing different questions. Of course independent checking of calculations is important for quality control. And yes, sometimes calculations are required to be submitted to fulfill permitting or contractual requirements. But those points are not central to the issue of whether calculations are instruments of service.

I was trained by one of the largest structural engineering firms in the U.S. to destroy the calculations after a project was complete. The reasoning was that the drawings and specifications were the real instruments of service. The calculations are only an intermediate step in the process of producing these instruments.

 

[flamby]

Taro,

I think I can not fully agree with you on this ideology. Engineering is more of science than art. It evolved in a scientific manner and is passed on to us by generations. To treat its rules, formula, proposition as personal thoughts does not do justice to its rightful owner - the world.

Our use of engineering and telling others how we used it goes very well with my mind when I see that what I was taught during my education far outweighs what I learnt on my own. Doctors and others doing something different does change this basic fact.

The calculations which is based on existing maths and engineering belongs to the world and is part of your service to the world. Without calculations, someday I would be specifying enormous sizes, without even calculating and still be as much of an engineer as the one who computes. Then everyone has a right to be an engineer, educated or not. And I can go on stretching this to insane limits...

Regards.

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