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]

My proposed solution has some additional history that may be of interest.

1) Long ago, a contractor asked me to come up with a DIY joist. It occupied my every waking thought for a solid, glorious month.

2) I designed the solution that I proposed above and the contractor procured the required material.

3) The contractor eventually changed their mind about self performing the joists fabrication and, instead, had a local fabricator tend to it using the material already procured.

4) The local fabricator assumed design responsibility for the joists and, in the process, went with a more conventional web-chord welding scheme. Otherwise, it's still my design.

 

[KootK]

@Celt83: I wonder if you might modify your seat as shown below:

1) With or without the double channel, I think that you capacity will be limited by the single.

2) This arrangement provides the following benefits:

a) Low profile.

b) Improved seat rollover capacity.

c) Bolted connection potential.

 

[Celt83]

yeah I do like that better it also adds the benefit of the welds being standard fillets as well.

I'm making a thing:

http://www.thestructuraltoolbox.com

(It's no Kootware and it will probably break but it's alive!)

 

[Brad805]

If you are talking low profile seats, I saw the detail below in the fall. Maybe it is common in other parts, but I had not seen it before. I was not the EOR, but if I were it would have gave me great pause.

 

[bones206]

I gotta call you out on this one

Yes! I know, I'm wayyy outside the box on this and was waiting for the wtf reaction haha. I guess it's just more fun for me to explore something really different than riff on a variation of the standard bar joist. I plan to follow up with some FEA to quantify just how bad this idea is.

I credit watching the Red Green Show as a kid with helping to develop this kind of lateral thinking ability.

 

[KootK]

Yes! I know, I'm wayyy outside the box on this and was waiting for the wtf reaction haha.

Alright, if you anticipated the objection then I rescind it and award your some bonus points for extreme boldness. Fortune does, in fact, favor the bold. And occasionally punish them mercilessly.

@EverbodyElse: you're a bunch of shameless cowards for leaving it to me to critique Bone's gonzo idea. Shameless. Cowards.

 

[Celt83]

bones206:
treat it like CLT and alternate the layup of the WWF maybe 45 degrees to get you less of a vierendeel setup.

I'm making a thing:

http://www.thestructuraltoolbox.com

(It's no Kootware and it will probably break but it's alive!)

 

[JoshPlumSE]

Idea #3:
What about a 3D truss with an equilateral triangular cross section? This essentially doubles up the top chord area (which is more prone to buckling) and less area for the more efficient tension chord.

Connections are that bad with triangles. In the communication tower, we frequently use shifflerized angles for our chords to make connections easier. And, we could do something similar here. Essentially, it would be a lattice tower on its side that is always loaded in the strongest direction.

For the diagonals, there are all kinds of options. But, the bent rounds suggested by Celt are actually reasonably common in latticed towers. And they would be CHEAP with easy connections.

Shipping would be more difficult because they would take up more space, but they would be a lot more stable during erection with roll over stability being much less of a problem.

We'd just have to come up with a way to seat these trusses on the girders that support them.

 

[kipfoot]

But I feel it would be poor form to submit a similar design with only minor modifications.

If it's better it's better.

For example: I chose to avoid extra cuts to shapes, favoring simplicity. But, if you were to cope the angle, a single angle web could be placed in such a way that reduces its eccentricity to 1/8" ish. This avoids flipping it over and has an eccentricity that we could more easily deal with. Maybe the labor saved in welding twice as many web pieces is worth the work to cope each piece.

 

[SwinnyGG]

Maybe the labor saved in welding twice as many web pieces is worth the work to cope each piece.

In defense of this approach - if you're building and selling these trusses at even moderate commercial scale, the cost to buy ironworker dies for coping and cutting to length of the angles in one operation would be trivial, and thus coping of the angle would add very close to zero additional fabrication time.

On another note, I don't know that I have a better or different solution than anything that's been posted so far. But, I LOVE the spirit of this type of thing. @KootK I'm willing to contribute another $50 to the prize fund.

 

[Celt83]

@Joshplum:
CFRP 3D Truss: Link

I'm making a thing:

http://www.thestructuraltoolbox.com

(It's no Kootware and it will probably break but it's alive!)

 

[bones206]

treat it like CLT and alternate the layup of the WWF maybe 45 degrees to get you less of a vierendeel setup.

I initially resisted that temptation due to the additional labor and waste, but probably necessary to have a chance of working mechanically. Reminds me of the old lattice style covered bridges.

 

[milkshakelake]

I'll give it a shot.

Simple cold formed steel truss with 2" deep tracks. It's basically a built up cold formed steel box beam, but with tracks as webs instead of sheet metal.

Pros:
-Can use same track size for chords and webs
-Each web element can be cut in the same way
-Easy to splice top/bottom chord if needed
-Screws are easy to install compared to welds
-If more shear capacity is needed near ends, welds can be used instead of screws

Cons:
-Can't put vertical webs
-Hard to put the "work point" in the correct place to avoid chord eccentricity
-Stronger than wood, but weaker than structural steel chords/webs

 

[dold]

Interesting concept with the WWF. It has inspired a similar and much more half-baked (less baked?) idea. Instead of WWF, what about roof deck with PAFs to WT chords on one side only. The jig would just need to hold the WT chords and then you'd lay the roof deck onto the webs and shoot it down. I suppose the deck ribs would need to be vertical to have any sort of web compression capacity. Design fastening (PAFs) based on shear flow demand plus vertical/direct gravity demand? Heavier fastening towards the ends of the joist. Probably be best to have end diagonals to form a closed "megapanel".

In a way I guess this would be similar to reinforcing a wood truss with plywood.

Perhaps this would be the fastest option to fabricate thus far. Definitely the ugliest. Definitely the jankiest. And like I said, totally half baked.

 

[bones206]

That's a creative idea. Sort of similar to that Simpson Strong Wall panel except the ribs are going in the other direction.

 

[Brad805]

I mocked up a sample truss of kipfoot's.

Notes:
1. Too heavy still.
2. Parts simple, and a jig would be easy to make.
3. Welds seem too light.
4. This is one of the lightest WT sections.

Time to get out the calculator and see where it is at capacity wise.

 

[KootK]

@KootK I'm willing to contribute another $50 to the prize fund.

Bitchin! I'll update the OP to reflect $200 USD.

This means that, if I can turn this around, I could come out $50 ahead. No divorce for me. Time to headhunt kipfoot's thing a little harder...

 

[KootK]

Probably be best to have end diagonals to form a closed "megapanel".

It seems to me that you'd need both a diagonal and a vertical at the end lest the truss itself kick a large diagonal point load into the decking. It's an interesting mechanical problem.

Ultimately, I suspect that the biggest armor chink for both this and Bone's concept would just be difficulty in running services through the joists.

 

[Lomarandil]

MSL, that was my line of thinking also. Having no exposure to the OWSJ world, I wasn't ready to propose it without running numbers on feasibility, but hearing that it isn't so far fetched may be enough to get me going.

Ultimately, I suspect that the biggest armor chink for both this and Bone's concept would just be difficulty in running services through the joists.

Much worse than your traditional sawzall hole through a wooden I-joist? I'd think the WWF would be easy to cut and reinforce (for services over 4"), and while the decking might require a reinforcement panel surrounding the opening.. still doesn't feel that onerous.

Edit: How thick is "roof decking" in your part of the world? I'm thinking of our 0.35mm stuff, but yours is likely thicker.
----
just call me Lo.

 

[milkshakelake]

@dold That's really creative. You could feasibly run pipes through it with some angle reinforcement. It reminds me of repurposing old shipping containers for homes and such.

@Lomarandil I didn't run any numbers. But if open web wood trusses can work, this can probably work too, just with less capacity than an OWSJ. I figured it would be for a janky solution where OWSJ's aren't in stock but there is a ton of cold formed steel lying around.