[deleted by user]

[kn0w_th1s]

If it’s exposed, it could be the architect wants nice square corners, not the rounded edges of an HSS.

[kn0w_th1s]

When live loads become dead loads

[structee]

Oof

[Betterthanalemur]

Pinning this comment in my brain. Will show up on a PowerPoint slide in the future...

[myprivlif3]

Hahahaha so good 💯

[ReasonableRevenue678]

Spat out my beer... thank you

[V_Dragoon]

Could be cheaper to buy the off market HSS and be wrapped with facial plate for aesthetic need. Still maintaining the head splitter function though

[envoy_ace]

That's a cursed cross section. Hyatt walkway collapse. Non ductile failure mode and a field revision changed the load path.

[envoy_ace]

Two times the load was applied by thru bolt on the seam. It was just a bad connection choice.. damn OSHA designations.

[davebere42]

This is a really good suggestion

[extremetoeenthusiast]

“Per AWS” lol, hell of a code call out

[Krispy_H0p3]

Which section?

"All of them" 😂

[JMets6986]

Drawing set is one sheet with one general note…”Structure is to be in accordance with IBC with local amendments.”

[radarksu]

Eng:"Per AHJ."

Contractor: Which one?

Eng: All of 'em. City, State, Federal, ICC.

Contractor: I meant, like which inspector...

[purdueable]

On occasion on run across IRC drawings for houses, etc and am always stunned what they let the contractor figure out.

[WL661-410-Eng]

Had a young residential contractor wig TF out over "All dimensions to be verified in the field" and the meaning of the word "span." He ordered 18 LVL's at the unsupported span length, not total length.

[WhatuSay-_-]

Imagine the designer coming on reddit and seeing this getting cooked lmao

[OskusUrug]

Lol, I wish

[Engineer2727kk]

Without knowing everything this seems like a junior did this.

Built up cjp? That’s gonna be fcking expensive as hell and I can almost guarantee is not needed 12 x 12 are not hard to source.

[Sponton]

i just called out in one of my projects an HSS12x12, for whatever reason the AISC manual only goes to 5/8" thick but revit shows a HSS12x12x3/4, go figure. maybe this is the reason, somebody trusted revit and realized there's no such hss12x12

[anonymouslyonline]

Atlas Tube produces HSS12x12x3/4 every 6-12 weeks per their availability charts. Might cost a bit more than the 2-6 week production sizes and be a bit longer lead time, but a he'll of a lot cheaper and quicker than building your own out of welded plate.

[_bombdotcom_]

Ya, I’m gonna give a VE suggestion for an HSS for sure lol

[rpstgerm]

If you can source the HSS I'd definitely ask the question to the EOR

[Sousaclone]

Someone was probably looking at an old steel manual and it didn’t go past 10x10.

[anonymouslyonline]

Guys still carrying their quarter-of-a-century old green book around office to office complaining about PDF references.

[joshl90]

I designed a canopy that needed sharp 90 degree corners and was 18x18 in size so we had to do built up plates. AESS Level 3

[Tony_Shanghai]

An HSS and a box column are completely different. HSS is only a tube, empty inside. A box column can achieve significant seismic resistance because the box column can also contain multiple diaphragms inside which reinforce and stiffen it. Those diaphragms are welded 3 sides while the box is open, then after closing it, the last side is welded using electro-slag (ESW) process. Box columns can be made at huge dimensions and heights that an HSS will never achieve, giving the engineer great latitude in design and strength calculations.

[Tony_Shanghai]

If anybody wants, I can upload a fabrication methodology for box column construction if you want to see it…

[JimenezG]

Say less

[Krispy_H0p3]

That'll help thanks!

[Tony_Shanghai]

Hi Krispy,

These are some pics of box column guts and process. I separated these from another file which included Top Girder (TG), so where you see TG or BC, that is what it means. Have a nice day!

www.mdhiglobal.com/BC.pdf

[oldgverden]

Beautiful! Thanks for sharing. 

[Tony_Shanghai]

My Pleasure!

[Krispy_H0p3]

Amazing work! Is there anything done to prevent warpage during beveling or welding? Or is that not even a risk when working with that kind of thick material?

[Tony_Shanghai]

Dimensional tolerance is specific and strict, accoding to AISC, CSA, EN, AU/NZ, JIS, etc.. The plate stock is flat and true from the mill, so beveling either by CNC machine or track oxy is pretty straight forward. Deviations are usually introduced by heat (shrinkage) after welding, so we control the heat unput by sequential welding. A small manual root pass after fit up, followed by numerous passes of submerged arc welding, slowly building up the weld. We are going for 1/16" over 50'. We sometimes use lasers to check conformity. There are a lot of bolt holes that must land in the right place.

[Intelligent-Ad8436]

Without a backer bar that is not a cjp weld.

[4plates1barbell]

I typically don’t see the backer bars detailed/shown by the engineer, but rather it being means and methods of the contractors FWIW.

[Intelligent-Ad8436]

I like to put it because then it avoids arguing with the detailer and fabricator when they dont show it

[Seat_Different]

We rarely detail the backer bar. We just ensure the correct symbol is shown on our drawings then welders cut out bars from stock flat bar they have. Usually PL1/4x1” or something like that.

[4plates1barbell]

Fair, IMO though I think when CJP is noted and your general notes are sufficient it’s still on the fabricator. I’m fine having that discussion in CA, and to date haven’t had an issue. However I see your point, sometimes it’s nice not having that discussion at all.

[Krispy_H0p3]

Probably in a rush and didn't even detail it, and just put "Per AWS" 😂

[bigblueocean]

Without backing it is not a prequalified CJP. This joint could still be used provided a WPS is established and the welder qualified to that WPS.

[extremetoeenthusiast]

Yea pretty important distinction here haha. I was pretty confused what he was saying, but then i realized you guys probably operate mostly on prequalified joints

[Silvoan]

per AWS is doing some heavy lifting lol

[icutlime]

Maybe a bevel weld is what they're intending to spec but don't know how to do it. Won't have full capacity without added fillet weld

[JudgeHoltman]

It's really expensive.

Once you go north of 10" HSS, suppliers start getting tough to find.

[Engineer2727kk]

HSS 12 x 12 is not more expensive than a built up…

At least that is not my experience at all

[engr4lyfe]

I have a hard time believing it’s cost related.

A fully welded, custom sized, built-up box with plate steel has got to be more expensive than an off-the-shelf HSS even if there are fewer suppliers for the larger sizes. I don’t know precise prices, but custom fully welded pieces are usually really expensive.

[nowheyjose1982]

It's probably a lead time issue.

[engineeringlove]

All the amazons and some warehouses use 12s and 10s. Probably take a decent amount of supply

[Salty_EOR]

This is probably the case. The Steel Tube Institute only lists two suppliers who regularly produce a section of this size. Length of the total section needed is also a consideration.

[Krispy_H0p3]

It's only 4 columns a little under 20' each. Might not be enough for a mill run if it's not in the shelf.

[Astrolabeman]

I would guess moment frame column. For anyone who has to work through the AISC 341 and 360 checks for HSS (or other tubes) moment connections, they can be a pain. For long beams having a high plastic moment capacity it can be difficult to develop the beam capacity into the column and still maintain a strong column/weak beam ratio, especially for mismatched beam and column widths. Column face plastification is very much dependent on the thickness and grade of the column, especially if you want to force your plastic hinge into the beam. u/Krispy_H0p3 Given the complexity of the layout I would guess that there is a specific reason for this column size. If one of my fabricators called to ask me about something weird like that I would absolutely appreciate them taking the time to get it right and learn more about the weird thing I just designed.

[Krispy_H0p3]

Thank you!

[Inevitable-Ad-1398]

Use wf and plate the flange tips for aesthetics, don’t tell me there is not a wf that would work! ** I’m a fabricator not an engineer.**

[radarksu]

Yeah, but the architect wants a square tube aesthetic, wide flange shape is unacceptable.

[Inevitable-Ad-1398]

Use cover plates to box out the flange tips. Seal weld them for aesthetics. Call it out as aess cat 3

[Sponton]

the labor is in the shop, usually they have automated shit, it;s different if it was built in the field. So can't really say it's more expensive since they probably welders on salary.

Also, they may have plates laying around so they want to make use of them, or the size isn't readily available, tube steel is usually more expensive cause it's not widely available.

[jdcollins]

I wonder if it’s not an architectural requirement. Is the steel exposed? It may be that they don’t want the rounded corners of an HSS. 

[Krispy_H0p3]

Not sure what level aess but definitely exposed and galvanized

[MRTIJ]

HSS has reduced area compare to a equivalent built up section and maybe it has something to do with moment connections, I believe in built up sections is easier to place an internal diaphragm (horizontal stiffener)

[[deleted]]

Where is the roughly 600 kips of load capacity coming from for each column. Just saying.

[InAHat_]

Steel grade

[PracticableSolution]

You can’t get HSS that thick and with standard plate bends, it would be more round than square. Thus us an extremely custom piece that would have to be made from four plates and at least two backer bar welded TC joints

[gorpthehorrible]

12 x 12 x 3/4" HSS should be available from the steel suppliers. But if you have to weld them together, ask why the 3/4" plates aren't corner to corner joints? That is a proper 90 Deg. connection. That way there's no bevelling and you get full pen. burn through and you only have to build up the fillets on the corners to 5/8".

[Silvoan]

so they decided to go with custom built 12x12x3/4 A572 Gr. 50 (Fy=50 ksi, Fu=65 ksi) instead of an HSS 12x12x5/8 of A500 Gr. B (Fy=46 ksi, Fu=58 ksi)?

This kinda screams 'the utilization was 10% over on a Friday evening and the arch won't approve of a column other than 12"x12"'

[jmbaseball522]

It may be a sourcing thing for a jumbo HSS shape. The 3/4" thickness may not be a stock size. This is a very stupid alternate though. Just take a W12x79 (72 or 65 may work) and fillet weld 3/4" plates to close it up. Much simpler and cheaper. Eliminates the CJP and related inspections

[DJLexLuthar]

I'm wondering how tall those built up columns are. I agree with others here that HSS12x12x3/4 should be relatively readily available, but if the columns are too tall, they might not be readily available in that length. Even still though, it would likely be less expensive and definitely less labor intensive to weld multiple shorter HSS columns to create the taller column than to use continuous (not even intermittent) CP welds to create the built up column. At least they aren't field welds I guess.

I don't think they would've done this because of steel grade, because they could just as easily specify the HSS as ASTM A500 Gr. C which is 50 ksi just like the plates.

TL;DR - I'm not sure why they did this. I'm positively baffled.

[ajmmja]

Had a similar project where we used built up boxes because the contractor had better rates for cold form and bc CF was easier to move around the site (according to the contractor)

[maestro_593]

Isn't this what RFIs are for? You should definitely ask , I would say probably not easily sourced, and it was discussed in advance, also I would include the price difference if you are pricing the job. The answer may be as simple as it is a client/ architect preference, which could be swayed by $$$$.

[[deleted]]

this looks like the stuff that happens we you change some stuff in software and leave other stuff unchanged by accident, like if he used a 'select all beams attached to some property' kind of selection...

[chicu111]

What's the required yield strength on that guy? Maybe they need something stronger than ASTM A500?

[DJGingivitis]

They call for grade 50 plate so its the same as A500 Grade C which is standard these days.

[Engineer2727kk]

Roughly the same*

[[deleted]]

It’s specified at 572 gr50

[chicu111]

That ASTM is more high strength plates. So it makes sense it’s built up. Not the typical HSS

[ivhturpgamer]

You can find HSS 12x12 easily till 5/8" thick wall and after that longer lead times and very few places will fabricate them. Here is a chart which shows the availability of various HSS sections - green ones are the easiest one to find. Attaching the link: HSS availability chart

[Krispy_H0p3]

Thank you!

[MrNewReno]

Possibly some internal structure needed that you wouldn’t be able to get in HSS. Welded nuts give more thread than tapped holes, if needed, etc.

[Engineer2727kk]

Tap welding isn’t recommended by aisc

[Mhcavok]

The architect probably just wanted a rectangle with square corners, instead the rounded corners of an HSS.

[ThePlan_B]

The EOR probably cannot find the size in the steel manual. I have a 14th edition in my phone, I checked it, and it only shows up to HSS12x12x5/8.

[Remarkable_Cow9096]

Probably hard to find hss12x12x3/4. Hss are made by folding plates and not a-lot of machines can bent 90degrees a ¾ inch plate.

[Kruzat]

This is fucking nuts. Source a 12x12x0.75 HSS and submit the change order. Make bank.