Modern Steel Construction Steel Quiz 12

[SteelPE]

I was looking at the steel quiz in the 10/17 issue of MSC. I was able to pick up the problem quickly as I'm sure others have. However, I had a slightly different answer, I came to the conclusions that the framing plan shown had beams that required themselves for support and therefore would not work. However the article simply states that the configuration is difficult to erect. Is the framing plan shown even structurally stable utilizing simple structural theory?

 

[bridgebuster]

I had nothing to do this morning & the weather wasn't conducive to painting.

 

[TehMightyEngineer]

Ta-da!

It's quite strong and stiff. Though lesson learned; if you're going to build one of these, don't use old wood from a decommissioned deck. The halved joints work great but when you're trying to get the reciprocal frame together it involves quite a bit of twisting, bending, hammering, and all the resulting cross-grain tension did not go over well on this old, weathered wood.

Oh well, nothing a few curse words and some long screws can't fix.

Makes a decent pull-up frame for exercise, too.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[DETstru]

TME...... this is amazing!

I can't believe one ET question about not even a real project has led to this! Fantastic!

 

[gravityandinertia]

I wonder if this was inspired by an engineer reading this post.

Human Reciprocal Frame

 

[TehMightyEngineer]

Hah! That was hilarious. It would be immensely gratifying if it was due to this thread but I don't have that much faith in serendipity.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[JAE]

gravityandinertia - that's great!

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[dik]

...anything more difficult?

Dik

 

[gravityandinertia]

I showed this video to someone who made a claim they did it in a class at school with 40 people! I know the math works out that everyone is essentially carrying about 1 body weight on their legs, but I still can't picture a 40 person circle of this. It would look insane!

 

[KootK]

I thought that the group might enjoy this example from my real life work this week. Precast hollow core plank. It's not sexy like the heavy timber but the erection and, to a lesser extent, performance concerns are there. It shall be rectified.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[TehMightyEngineer]

Naw, leave it, take pictures of the construction afterwards for fake internet points. All the cool engineers are doing it.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[jayrod12]

You need to tell your mechanical guy he missed putting full width holes in the other two planks adjacent these two.

 

[EZBuilding]

This thread made it's way back to AISC's Modern Steel Construction. Take a look at the editor's letter on page 6.

Link

Reading that letter made me think back to the video below. The Atlanta Falcon's new roof has to at least be partially considered a reciprocal frame!

Link

 

[TehMightyEngineer]

This thread made it's way back to AISC's Modern Steel Construction. Take a look at the editor's letter on page 6.

That brought a huge smile reading that. Much appreciated for the link EZ. Of course I shouldn't be surprised that they saw the thread but I'm glad our exuberance of "nerding out" over this topic made it back to them and even beyond to Mr. Kruth. Definitely shows that the passion for structural engineering is alive and well at all levels of the profession.

All in favor of a monthly discussion thread on future steel quiz topics say "aye"?



Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[cal91]

That is awesome! Haha I love the recap of this infinitely long thread.

 

[TLHS]

I missed the discussion, but jumping back to the matter of determinancy.

The practical definition of determinancy make it pretty obvious (in additional to the mathematical definition that Cal pointed out):

Removal of any degree of freedom from the supports will result in failure.
Addition of a hinge or roller or other release within a member will result in failure

There is no redundancy, therefore it is statically determinant.

 

[bridgebuster]

This thread made the December issue of Modern Steel Construction.

 

[TLHS]

Hahahaha

But through it all, my favorite comment came from Larry Kruth, AISC's vice president of engineering and research, after viewing the thread: "Should we let them know this framing is actually in a building constructed in the 1990s? It was stable and remains so after erection

(It's the editor's note on page 6)