If there was a progression in the mind of a structural engineer, I think it is similar to the one that the philosopher Friedrich Nietzsche wrote about in “Twilight of the Idols” (see MSC article). While Nietzsche was generally referring to raising the human spirit to a higher level, it is similar to my experience, going from 1 to 6, as a structural engineer over the fifteen years:

1. The ”truth” of structural design – is attainable for the sage, the pious, the virtuous man.

2. The “truth” of structural design – unattainable for now, but promised for the sage, the pious, the virtuous man.

3. The “truth” of structural design – unattainable, indemonstrable; but the very thought of it – a consolation, an obligation, an imperative.

4. The “truth” of structural design – unattainable? At any rate, unattained. And being unattained, also unknown. Consequently, not consoling, redeeming, or obligating: how could something unknown obligate us?

5. The “truth” of structural design – an idea which is no longer good for anything, not even obligating – an idea which has become useless and superfluous – consequently, a refuted idea: let us abolish it!

6. The “truth” of structural design — we have abolished. What world has remained? The apparent one perhaps? But no! With the true world we have also abolished the apparent one.

Thus, we have abolished truth in practice even if we pretend it still exists in school. Good enough is enough in practice (i.e. a good enough design decision = a correct answer). That doesn’t make it easy, “good enough” is actually very hard. It is apparent in this progression the great extent to which the individual engineer can influence the design. I have found that the design of structures is less dispassionate and logical than I used to earlier in my career. There are no clear-cut answers to the complex and diverse problems we face. This is not to diminish the role of analytical tools to assimilate knowledge of phenomenon, it is just that it is simply not enough.

(E Nelson,  portion of MSC Twilight of the Idols)

Note:   Part 8 should be “Kick Ass” (or “Kick Butt”), but the editors of STRUCTURE changed it to “Be Aggressive” unfortunately.

Uncomfortable decisions are by far the most common of my dreams.  These are engineering decisions that are made without the best understanding of how the part or system will perform (very common daily decisions when unique details or structures are developed).  This is why engineering is a profession.   We need to pull things out of a hat sometimes and live with them.  Part of the anxiety of a structural engineer is that we are solving problems that never existed before, we are inventing something new.    Yes, physics doesn’t change, but that is about the only thing that doesn’t.   Every building has traits that no other building in the world has, and have we verified everything?   Of course not.   But have we verified everything we know how to verify?  After all the calculations are applied, we still have to make a decision about whether it should be built a particular way or be changed.  Eventually we have to say yes, “no exceptions taken” and live with it the rest of our lives.   Crazy things get built and amazing engineers are the creative force behind all of them.  How many structures out there do we lose sleep on?  Maybe 2-3 per year on average?

I am particularly suspicious of the idea that our masterbuilders, craftmen, and masons of the past did not understand flexure and compression basics (top of beam is in compression for example or rules for column slenderness).    They may not have had the proper formulas but they certainly had a better intuition than we give them credit.  Yes, Leonardo Da Vinci and Galileo were the first to “discover” bending stress by writing it down, but it was used as rules of thumb by our builders well before that time.

In the book “Structural Engineering:  The Nature and Theory of Design” William Addis quotes the following statement from Karl Terzaghi challenging the idea that theorey leads to practice:

History shows us that there is hardly a single concept of practical importance in the field of structural engineering that was not instinctively anticipated and used with success in design and construction by individuals or groups of engineers many centuries before applied mechanics came into existence.

In Henry Petroski’s book Remaking the World, he states:

Some of the first modern engineers did not apply science but rather led science.  The science of thermodynamics may be viewed as an application of steam engines, and rational structural analysis as an application of bridge building.   The view of scientific discovery as depending on the ingenious craftsmanship of instruments, and thus following technology, convincingly flies in the face of the conventional wisdom that technology is mere applied science.  [Petroski, 1997, 17]

So according to this, Science is Applied Engineering