In writing, the first draft almost always sucks. After proofreading it the first time, it gets less shitty. Refine it a few more times and the first draft that sucked is now a winning piece in a literary contest. How did the sucker-turned-winner article transform? By re-reading, editing and rewriting. There’s just no shortcut to that. Repeating again and again and again is the only key.
So how does this introduction relate to structural engineering?
Repetition is the key to mastery and developing what I’ll the structural engineer’s structural gut feel. More than learning the most sophisticated software, more than memorizing the American and British codes, the structural gut feel is the most important skill a structural engineer will ever develop and it is something that he must possess. It’s what separates the machines from us humans. The real structural engineers from the structural technicians/encoders. Why? Because it is the structural gut feel that tells you that something’s just isn’t right. And when you are already an experienced designer, you will know that something’s not right just by relying on that gut feel.
And the thing is, it’s almost always right 99% of the time.
I learned the importance of which the hard way on a certain hotel building I was designing somewhere in Palm Jumeirah in UAE. (I am not saying that I already acquired a fully developed structural gut feel. There’s no such thing, as far as I know. It is a continuous process that goes on all throughout our professional lives as engineers.) We already submitted the for-construction drawings along with the design calculations. However, there are some more changes in the architectural plans. And since my hands were full at that time, an officemate of mine applied the said changes in the model and re-ran the design. The changes are minimal and are expected not to have an impact on the design. But to our horror, a big portion of the wall is failing in PMM (axial and bending). The provided reinforcement in the plans was T20-200 but he was getting a minimum of T25-150! That’s for a 300mm thick core wall so you can just imagine the big difference in the required ρ-value of reinforcement!
I am right and they are wrong, I told myself. I diligently did my responsibilities of ensuring that everything from the columns, walls, and piled raft are designed with a sound engineering judgement to the best of my abilities.
I tried to trace what went wrong and I found out that the culprit was the balancing of the static earthquake to the dynamic response spectra case, I forgot to balance it! It was later revealed by my own investigation that the dynamic earthquake case governs the design of that part of the shear wall, with the aid of the story shear plot. The static earthquake load case on the x direction are smaller and thus it cannot compensate for the effects of the balanced dynamic case.
With a bruised ego I tried to explain this to my senior and luckily, he never scolded me nor blamed my shortcoming. But of course I was so humiliated of my mistake.
After which, I browsed through my wall schedule mark-ups and found out that my initial reinforcement was T25-150 and the new mark-up was T20-200. So! I should’ve questioned the result in the first place. If it transitioned from T20-200 to T20-175 I would’ve known that I’m right on track. I mean the results would be somewhat consistent. But with a jump that drastic, something’s really off because it would take a significant change in framing or loading to increase it by that much.
So how did this mistake led me to develop my structural gut feel? First, this showed me the importance to know and predict trends. So how did I accomplish this? I kept records. Every run I extract pertinent tables and compare. It seemed stupid at first and a waste of time but I persisted. I scrutinized every detail such as base reactions for example. The self-weight global reaction increased. Should it increase in the first place? Have I thickened slabs, walls or increased the sizes of columns and beams? Or did I make an error in the geometry definition?
Observe trends. Ever noticed why the bending moment at the interface of the pile cap supporting a wall or column and the piled raft increases with additional axial load given a constant hydrostatic uplift? See what I mean?
Make observations. Ask why. Does it make sense? If in doubt, dig some more, punch in the digits. Numbers don’t lie in structural engineering.
Do you get to fully develop this structural gut feel in just one project? By any means no. The oldest and most experienced structural engineer will never be able to experience EVERYTHING in structural design. Is this an easy task? No. Never is, never was, never will be. It will involve tedious calculations, late night technical soliloquys, determination and very hard work.
The structural engineer is never afraid of hard work because it’s his ally, he grows in it, he becomes wiser and it develops his structural gut feel that even if he sees only the structural drawings, he senses that something is wrong even if he still didn’t see the calculations. He feels it, and he is right. And thus he validates his hunch and develop solutions until his gut feeling already returns a satisfied and confident vibe.