open web steel joist on metal stud wall? 1

[BSE05]

I have a case where the architect wants to bear 40ft span open web steel joist flat roof on a metal stud wall. Does anyone know where I can go for design guidance on the metal stud wall. I can tighten up the joist spacing to reduce the point load. at 3' spacing 3K point load to wall.

Or is this just one bad idea?

 

[SlideRuleEra]

http://www.rinker.com/steelcon/downloads/ProductTechnicalInformation.pdf

http://www.SlideRuleEra.net

 

[UcfSE]

You need something to help distribute the load on the wall. Transmitting a 3k load through a single track will be difficult to do correctly. Something such as a built-up header or a steel tube for the joists to bear on would work better. As long as you run all of the numbers it should be fine, but don't cut any corners. That is a lot to put on metal studs, especially if you have a significant lateral load. Make sure to account for any eccentricity due to the joists also. Even though they may bear on the wall, if the resultant of the reaction isn't through the center of the wall you still have some added bending moment.

 

[sundale]

Most roof structures like the one you describe are bar joists with hot rolled steel spandrel beams and cold formed steel curtain walls. There is most likely a good reason(s) for this...

Most flat roofs have a parapet which is easy to accomplish with curtain wall studs running past the spandrel. With a bearing wall stud system, your parapet system will have to be "sticker" studs with a complicated attachment (welds, kickers, etc.)

I completely agree with UcfSE that you will need some sort of continuous header to distribute the point loads from the bar joist seats into the studs. The studs perhaps work with this large axial load (and any eccentricities); you are probably looking at 8" studs depending on your plate height.

Your easier and thus cheaper structure is probably bar joists at 5' or 6' o.c. with a metal deck roof with steel spandrel beams and stud curtain walls. The wall details are traditional "no brainers" and the steel beams make a great diaphragm chord.

 

[BSE05]

The reason for this odd construction is that this is a second story addition on top of existing masonry load bearing walls. circa early 1970's The intent is to keep the wall weight and load to grade wall footings down. I'm in the process of running the loads, and trying to convince myself that this bearing stud wall is feasible.

sundale - when you say steel spandrel beams do you mean on top of the metal stud wall or a typical steel frame with columns?

 

[BSE05]

slideruleera- thanks that looks like just what I need. I found something similar but not as detailed with Marino metal stud. By the way I have a great "calculator" for you. I need to scan it, circa 1912 Des Moines Bridge & Iron, for the design water stand pipes. I'll e it to you soon.

 

[sundale]

I was assuming a new building with a steel frame. You could put a continuous tube steel or built stud header on top of your framing. Why not wood trusses and studs? Fire rating?

Modifying an existing building with a "pop top" is an entirely different matter. A 1970's building does not meet current code requirements "as is", much less with another story of gravity and lateral loads. Have fun and I hope you guys have a good structural fee.

 

[BSE05]

Sundale --Yes all noncombustible construction.

No drawings on the existing masonry which is most likely non reinforced!

This is going to get ugly. I may have to suggest jumping over, around or through the lower building with a new braced steel frame and foundations. The architect of course has no idea this is coming. And the added cost could kill this project.

 

[SlideRuleEra]

SteelyLee - Glad it was of help. Will look forward to receiving your "calculator" scan.

http://www.SlideRuleEra.net

 

[sundale]

Many "pop top" projects require a priest, not a structural engineer. Ugly is right.