Concrete Filled Metal Pan Stairs 1

[dik]

Is there a table that gives the gauge required for concrete filled metal pan stair treads. I've seen gauges from 16ga to 10ga used for typical spans of about 3'6 max, with 1-1/2 concrete treads. Something like:

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dik]

found it... NAAMI Looks like 14ga works for a 3'6 wide stair.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dik]

Is there an issue with 1/8" fillet welding of 14ga material? warping and distortion? can this be minimised?

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Demented]

That all will depend on the welder, the process, and how much weld you're wanting/needing, but I highly doubt there will be much of an issue. Typically what I've seen called out and have done countless times with zero warping issue is 2" long welds from either end with a 1" or 2" weld in the center for connection to the stringer (typically also sitting on stitch welded 1"x1"x.25" angle with 3/16" fillets). Along the width of the treads, typically 1" stitch welds with 6" spacings between. Distortion can be minimized even further by adding chill material opposite to the face of the weld if at all possible, but is overkill. You'll typically find most pre-manufactured pans to already have some level or warp and distortion to them. The shop's ability to maintain proper tread angles and height is going to be your biggest concern from my own experience with 27*-35* being a likely range along or among different spans on 11" depth treads.

 

[dik]

Thanks Demented... Looking at 1-1/2@12, or a couple of 1" at discreet locations.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Demented]

1.5@12 wrapping the corners should do. I've seen less hold more weight no issue with subpar welds too. Though I always find it best to have that stitch in the middle just in case; it'll take maybe an additional 20 seconds and few cents worth of wire per tread and is worth the assurance knowing it's not going to budge. Most guys will skip any material prep and just want to burn through what ever millscale or galvanizing is there if any so it wont hurt anything or cause any additional warpage.

I've so noticed a +/- 0.25" on widths of pans from manufacturers so the additional weld could even be beneficial in making the pans more ridged to prevent any cracking from the concrete over time due to pans wanting to flex.

Precision guess work based on information provided by those of questionable knowledge

 

[dik]

Thanks for the advice... will modify my standard detail. The last project had 1/8" sheet, and I thought it was heavier than my design loads...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Demented]

Sounds like a good spot to hide in a Tornado.

Precision guess work based on information provided by those of questionable knowledge

 

[dik]

thanks... I'd have to increase the fillet welds to 1/4"...current trend is to avoid the nosing and slope the riser... I think this increases the chances of buckling or warping from welding due to the lack of stiffness on the face of the riser. I'm just checking to see if a nosing is still permitted.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Demented]

I agree that it would definitely increase buckling and warping. I've seen this overcome by angle or HSS, in various lengths, welded to the back of the risers and bottom of the tread. Usually 1.5"x1.5"x.25 angle or 1.5"x1.5"x11G box. This just adds more cost, weight, and manufacturing time and doesn't completely eliminate the warpage. With the nosing, you're able to get a smaller, but still more than adequate weld underneath, with 1"@12". Overall there will be much less heat going into the material which is the cure I feel. Especially if there will be any 4G, or an inspector that is unhappy they can't get their fillet gauge inside the radius and demand more weld which throws even more heat into it.

 

[dik]

The reason for the 1-1/2 is that it's the shortest structural weld.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Demented]

If you're going for structural welds in that location, all the power to you. I've only ever seen tacks called out there, as it's been assumed the weight of concrete or stamped steel treads would be the bearing force to keep the bans down. The tacks in that location at the last shop I was at we fabricated pan stairs, we only began the tacking at the 1"@12" due to one situation where someone was walking around with a off-cut off #11 he found on the site and was slamming it up into the bottom of the stairs. I'm unsure if that's to code in this state, but I'll definitely keep that in mind for if I ever see tack denotations again.

Precision guess work based on information provided by those of questionable knowledge