CAST YOUR VOTE! The Great DIY Steel Joist Detailing Competition of 2022 - Win $250 USD 30

[KootK]

Things have been a little slow around here lately for my liking. In an attempt to liven things up, I'm attempting something experimental: an engineering contest with a cash prize of $150 USD. This is your chance to:

A) Earn yourself some KootBucks and;

B) Establish yourself as a GSEL (Goddam Structural Engineering Legend).

THE CHALLENGE

In the spirit of times, develop a scheme for the fabrication of a steel joist that would be fabricated on site rather than by a conventional joist supplier (Vulcraft, Canam, etc).

THE RULES

1) Include sketches or be forever disparaged.

2) Describe the benefits of your proposal as you see them.

3) Submissions will be accepted until midnight on June 5th, Pacific Time.

4) On June 6th, voting will commence.

5) Voting will close at midnight on June 12th, Pacific Time

5) Votes will be cast by way of members visiting the thread and writing a quick note to indicate their favorite scheme.

6) Votes will NOT be cast by way of giving out little purple stars. Give out all the little purple stars that you wish but none will be recorded as a formal vote.

7) Anyone may enter the contest and win the prize. However, you need to have received at least 9 little purple stars on this forum in the past in order to qualify as a judge and cast a vote that will be counted. I'm setting this restriction only as an attempt to prevent this thing from spiraling into some weird, spammy, cheating affair. Basically, if you're to be in charge of awarding the KootBucks, you need a reputation.

8) The prize will be awarded in the form of an Amazon eGift card. The winner will need to send their burner email address to my burner address or whatever. We're smart kids, we'll figure it out.

9) No prize will be awarded if there are not at least five entries to choose from, including my own.

10) If JAE shows up to judge, he can cast my vote along with his own.

May the best engineer win!

 

[KootK]

kootk - you probably don't want to drag this on for too long, but for the sake of comparing apples to apples, it'd be interesting to set a span and basic design criteria to see how some of these concepts compare to each other

Oh no, I'd love to drag this out forever if it could remain interesting forever. That said, I think that it would be a lot to ask busy folks numerically evaluate their solutions so I'm skeptical that could be made to happen. And some of the more interesting solutions have exotic aspects to them that might be difficult to try to evaluate. That said, perhaps the 25' example that I used for milkshake's proposal could be used for benchmarking if anyone is feeling ambitious enough to run some numbers.

I'm already pretty happy about the number of cool sketches that have been posted here for harvesting. That may have to be enough.

 

[milkshakelake]

@KootK I was going for the easiest possible fabrication. Thanks for running some numbers on my scheme. About getting maximum 8 screws into the connection: this will make it infeasible, but just for funsies, one could use custom deep tracks and it would also help with the compression/buckling. At that point though, it's not really DIY.

My votes are:

1. Enable's scaffolding truss idea - Seems feasible to make on site. (Similar issues as my truss though.) I'm voting based on the feasibility and DIY-ness of it, and if it makes sense to field smack a bunch of members together as opposed to buying steel beams.

2. canwesteng's "unistrut" idea - Seems super easy to install. I don't think it stacks up fairly to the other entries since some prefabricated members are used, therefore it gets an honorable second place.

3. dold's metal deck joist - I like the ballsiness of this idea, and it's my favorite. I'm just iffy about how accurately it can be calculated. 1 and 2 are much more traditional and proven calculations.

 

[bridgeDisciple]

I have been observing this very interesting contest from afar. This is a question, NOT a submission (i think the entry deadline has passed anyway, and i'm not offering sketches). A number of companies have arrived in the "lightweight steel frame" space - (prescientco.com, scottsdalesteelframes.com). Scottsdale specifically offers its factory in a box - containerized truss builder system - for on-site truss building. Theirs are bolted, not welded, but are aimed at floor and roof support structures. If i understand the gist of the contest, joist suppliers are currently a bottleneck motivating you to look for local and DIY-on-site alternatives. So my question is, "could the Scottsdale system have qualified for your contest"?

 

[canwesteng]

I'll confess I wasn't aware of that... seems to make my concept largely redundant

https://www.youtube.com/watch?v=

http://WWW1Lx2KHYo

 

[KootK]

I was going for the easiest possible fabrication.

And you rocked that, clearly.

Thanks for running some numbers on my scheme.

I didn't actually run any numbers on your scheme. Rather, what I did was put some numbers to the demand side of things without addressing the capacity side in any way. My hope was that someone with more CFM chops than I have would pick up the mantle on that and truly run some numbers. Most of my CFM work is just making use of tabulated designs. I know enough about the fundamentals to dig deeper and sort out more exotic situations when I need to but that takes time... time that I don't have with respect to servicing this thread / contest.

That said, I'll give the capacity thing a poor man's go and hope that any mistakes that I make will be picked up by someone more knowledgeable. What follows is what I initially considered the major design issues for this truss typology.

1) SCREW CONNECTION CAPACITY

About getting maximum 8 screws into the connection: this will make it infeasible

Will it make it infeasible? The first graphic below leads me to believe that with 16 ga, 50 ksi material and 8-#10 screws, we could get about 4,300 lbs out of each web to chord connection. That would be plenty.

2) CHORD TRACK LEG SHEAR CAPACITY

The CFM setup has a feature that I initially considered likely to be problematic: see the second graphic below. For a short time, all of the truss vertical shear must live within the track leg. I originally thought that would be a deal breaker. I may be out to lunch with that however. If you do a shear yielding capacity check [0.9 x 0.6 x As x Fy), you get twice the required capacity. I suspect that there's also a shear buckling check that one could do that would likely be much more limiting. On the other hand, the presence of the connection itself does a fair bit to brace the track leg against that I would think. How to prove that rather than just assume it, I don't know short of testing.

3) CHORD AXIAL CAPACITY

This is the one that I have the most trouble evaluating without a deep dive. Using a gross Ig rather than an effective one, the Euler buckling capacity again comes in well in excess of what I've estimated is required. See the last two graphics below.

This all strikes me as too good to be true but maybe I just don't have a good feel the capacity of CFM members.

 

[KootK]

So my question is, "could the Scottsdale system have qualified for your contest"?

It could have and still can as far as I'm concerned. In my opinion, qualification for entry here doesn't necessarily mean "original". Many of the entries here are non-original. Rather, I feel that qualification simply means:

1) The scheme could be executed by a contractor or fabricator who's not specialized in the mass production of the scheme.

2) The scheme needs to be evaluated in the context of its being executed by a contractor or fabricator who's not specialized in the mass production of the scheme.

So the Scottsdale concept ought to be evaluated assuming that it would be someone other than Scottsdale supplying and fabricating the trusses, that's all.

I'll confess I wasn't aware of that... seems to make my concept largely redundant

Per the above, I don't feel that the Scottsdale thing does make your concept redundant. In effect, the Scottsdale solution might be viewed as a permutation of your submission.

 

[Lomarandil]

I'm away from home at the moment, but have a rather rough CF channel capacity SMath sheet up in the open source group if anyone wants to run that for a slightly more refined take on MSLs proposal.

If it's still relevant to the discussion when I get back, I'll run it then.

----
just call me Lo.

 

[WinelandV]

I'll put some voting in:

1) Dold's roof deck web, just for the creativity. Possible upgrade would be to sheet it on both sides of the chords, to help alleviate Koot's concern about flexural torsional buckling (yes, this would make fab-ing it more difficult). I also like it b/c I think it would be easy, quick, and cheap enough to give a local University 50K and get some testing done on it.

2) Enable's Jericho Reborn - the end seat speaks to me.

3) KootK's HSS Option #2 - because I like tube sections.

 

[KootK]

If it's still relevant to the discussion when I get back, I'll run it then.

That would be peachy if you're willing. If nobody can refute the rosy numbers that I ballparked, I'll be compelled to change my first place vote to Milkshake's scheme.

 

[milkshakelake]

@KootK Regarding the screw capacity, that's pretty much in line with how I'd calculate it.

Regarding axial capacity, I did a quick run on a black box type program called CFS and got a compression capacity of 6.4 kips, much lower than yours.

Using heavier 12 GA track pushes the compression capacity up to 17.6 kips assuming fully braced. It's not actually fully braced, but I'd need to do a deep dive to get further than that...we can just say it's roughly 12 kips. 12 GA is still viable and screwable. 10 GA is where things get hairy.

 

[kipfoot]

I'm actually considering using this concept as part of a roof reinforcement, so I'll cast my vote for the kipfoot WT and L truss (2 Jun 22).

2nd) the milkshakelake cold formed shape truss.
3rd) the Celt83 homemade bar joist

 

[Lomarandil]

Sorry for the delay... I didn't have axial capacity in my sheet yet after all.

I also get about 6.6 kips capacity out of a 54mil track if the decking doesn't restrain chord twist (or 8.6 kips if it does). (My ignorance of the context shows -- which assumption would be typical?)

Going up to 12Ga, I get 16 kips unrestrained.

----
just call me Lo.

 

[phamENG]

So...who won?

 

[WillisV]

Yeh, who won?

 

[KootK]

Sorry, I let this stretch on too long and then had family in town.

By my count, it is MilkShakeLake that has won! That, particularly now that I've been forced to vote for him myself.

Some administrative stuff:

1) I'll coordinate the payment of my $$$ to MSL. Conveniently, I already know how to reach him.

2) The other two gentlemen who have generously contributed to the pot can either:

a) Make their own arrangements with MSL or;

b) Make arrangements with me that I can then forward to MSL.

Whatever's most convenient.

Congratulations MilkShakeLake! And thanks to everyone who participated.

 

[Brad805]

Searching for steel stud truss suppliers yesterday I see we have someone that has developed a large scale production method for this: FrameCAD They have software and equipment to mass produce these. Here is a video of their machine making the truss parts Truss Part Fabrication

 

[milkshakelake]

Thanks everyone!! Lots of great ideas in here, and I'm honored to be a part of this. Thanks to everyone who participated, supported it, and especially KootK for starting the idea.

 

[Enable]

Congrats milkshakelake!

For me it would most likely be easier to transfer to KootK, and he in turn transfers to MLS. One primary reason for this on my end is that I’m pretty sure my bank is only setup to e-transfer in CND and the competition is in USD. But pretty sure KootK deals in both so he'd be probably setup for that. I’ll make sure to send equivalent CND + exchange fee that’ll occur on KootK’s end.

KootK the email I reached you at last time is best to e-transfer it to, yeah? If so password will be: OWSJ

 

[KootK]

KootK the email I reached you at last time is best to e-transfer it to, yeah? If so password will be: OWSJ

That's fine but I don't recall receiving an email from you previously.

kootenaykid
hotmail
COM

 

[kipfoot]

In my opinion, a truss using cold formed shapes is a practical and effective answer in the spirit of KootK's challenge.

Congrats to milkshakelake!