Cutting Edge Insights
with Dr. Lee

Structural Design

“Engineers do engineering work, and developers do development work.”

Further, builders build, realtors sell, doctors examine and diagnose, and speakers….speak.

Sounds great to me, if life works out smoothly and as anticipated in all aspects.

As we all know, that isn’t precisely true.

I’m not a structural engineer, nor do I want to be one. Fortunately for me, I know structural engineers. Also, fortunately for me, I can rely on them for calculations of wind loads, point loads, recommendations of fasteners, structural slab design characteristics, etc. The important thing is to know when you need one. The Michigan Building Code is prescriptive in nature, which in essence means “if you want x, do y” but any time your needs fall off the beaten path, which trust me, they always do, it’s great to have an engineer in your corner.

Recently, I realized I needed to provide some steel support columns to hold up an LVL (an acronym for laminated veneer lumber, an engineered piece of wood which in my case was acting as a girder) which in turn was going to hold up several floor trusses which in turn supported a good portion of the main floor of a house. I needed to provide 2 such columns before the framers got to the jobsite. Actually, I could have waited and delegated this task to the framers…but delegating the decision of which columns to obtain and install wasn’t high on my list of tasks to delegate – (Read on and you’ll know why.)

“What is the point load at each end of the LVL girder?” I had asked my structural engineer.

“13,000 pounds”, he told me.

OK, no problem. Steel columns are available in all shapes, sizes, lengths, and loading capacities.

Visited my local lumberyard. Knowing that the exact predicted length was   8’ 1 ⅝” but not wanting to rely on a theoretical precise length due to variables beyond my control, I knew I needed an adjustable column in the 8’ 0” to 8’ 4” designation. Up or down an inch or so to provide perfect loading and bearing. Cool.

The problem was, the sticker on the column (see below) indicated that for my desired length, the loading capacity was 10,180 pounds via the “Allowable Stress Design” (ASD) method, but 16,290 pounds according to the “Load Resistance Design Factor” (LRFD) logic.

Called my structural engineer. “You need to exceed the anticipated loading with the ASD design; you’ll need a stronger column.” he said.

I think that was his way of saying “I don’t have time to teach you the theory; take my word and get a more robust column.”

I also noticed that the label indicated that the column was 0.120 inches thick, about an eighth of an inch. I remember once my dad had fabricated some support columns when I was remodeling my basement, and he had used schedule 40 steel, which I learned was about ¼ inch thick. I don’t know for sure, but my rudimentary investigation yields that the “pipe schedule” refers to wall thickness, which increases with increasing schedule number. But thickness also increases with increasing pipe diameter.

As we were replacing the undersized, “homeowner special” thin-walled steel columns, I remember my dad telling me, “If you don’t like 4-inch schedule 40 steel, keep in mind that 6-inch schedule 40 steel is holding up the Mackinac Bridge.” OK, point made.

Anyway, the local lumberyard was not certain of the lead time with which they could provide the more robust schedule 40 columns, but they recommended a steel supplier about 20 miles away.

Notice on the sticker below that the “ASD Allowable Load” is 25,580 pounds (the LFRD is over 40,000 pounds) so I know I’m in good shape for the 13,000 pound requirement from the engineer.

(I wonder if my structural engineer introduces his own safety factor into the calculation.)

If you’re observant, you’ll also have noticed that the stronger column was listed as 8’ 3” to 8’ 7” which is altogether longer than my needs.

Yep… They erroneously made it out of a longer piece then had to cut it down and re-weld the bearing plate to the column when they realized they had screwed up.

No big deal. Another 40 mile round trip for me to pick them up. Life is too short to get bent out of shape over the little things. I know this because I was able to ruminate about life on the way there and back.

Q: What the heck do “ASD” and “LFRD” really mean?

A: Well, I’ve included some links in the reference section below.

Most likely, all you need to do is glance at each one for 10 seconds and be thankful that you do what you do, and you don’t have to understand that stuff.

I took about 30 minutes to try and understand the differences, and I have to confess that I still don’t.

I’ll take real estate construction and development over engineering equations any day of the week. And I’ve always been good at math.

That reminds me of what Robert Kiyosaki (bestselling author of Rich Dad, Poor Dad) has said more than once (paraphrased by me):

I’d rather be a generalist than a specialist, because if I know at least a little bit about many different disciplines, I’ll know who to ask and what to ask to obtain the answers to very specific and detailed questions that invariably come up in real estate projects and in life.

Not a bad philosophy.

Before you think, “those equations are rocket science to me,” revisit my earlier article where I defined rocket science here.

Is there a moral to this story? Yes! It is: When in doubt, take the most conservative requirement and exceed it. If nothing else, your structure is more likely to hold up in a tornado. Don’t risk being the next Surfside condo disaster. Again, life is too short. (See previous article about that here.)

As you think about that, you’ll more likely find me looking at the big picture of real estate development rather than drilling down into the likes of:

M1 = ∫aa+b wx(L-x)2dx/L2

Real estate development is soooo much more fun.

Until next time,

Dr. Lee Newton

How A Doctor Learned To Develop Real Estate

References:

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