Design of HSS Beam-Columns 1

[EV11]

Hi everyone,

I'm an engineer in training from Canada that has been working in the design / analysis of buildings for 1 year now and I am new to this forum.

I am currently working on the design of a very standard one-storey structural steel building (80' x 120' retail store, 14' column height). I have a question regarding the design of exterior columns (beam-columns, subjected to axial loads and bending moment). I have always seen wide flange steel members used as exterior columns for steel buildings in previous designs, and when studying beam-columns in school.

My question is - can HSS steel members (square hollow sections) be used for exterior columns in steel buildings? If so, why isn't it more common to see this used in structural steel buildings?

The project architect would like to use HSS members for the exterior columns of the building because these would work better with the wall assembly that he is envisioning.

As mentioned before, every beam-column design example that I have done in the past, or have come across online/in books, have used wide flange steel members.

Is the design procedure for HSS beam-columns similar to the design procedure for wide flange beam-columns? Are there any things that I should consider before getting into it?

If anyone has any design examples/material or literature on this subject that I could use as reference it would be greatly appreciated as I'm having trouble finding information online or in my textbooks.

Thank you.

 

[phamENG]

Yes, this is quite common. Where I practice, essentially every small commercial steel building like this that I've designed has had HSS columns.

The reason they're not more prevalent generally is the cost. The manufacturing process for HSS is a lot different than WF beams and other rolled shapes, so the $/ton is a good bit higher. On a small building it doesn't make much of a difference, but starting doing 15 story buildings and the cost difference (and weight) adds up in a hurry.

I'll let some of the other Canadian engineers chime in with relevant code references and examples using your codes.

 

[jayrod12]

phamENG has it again, on small projects the increased cost per pound of steel is relatively non-noticeable and they are more aesthetically pleasing. So on many of the strip mall type projects, HSS columns are go-to.

The connections are also a bit more a bear when it comes to multi-storey projects, as well as splicing details aren't as clean unless they get expensive. So once you exceed a reasonable column length and need to splice them, then wide flange columns become much more desirable.

Design of them is no different that wide flange in the sense that you just go through clauses 13.5 and 13.6 for bending capacity and clause 13.8 for combined loading.

 

[dik]

As pham noted... they are quite common. It used to be that if the column was more than about 15' high they were more economical than W shapes... this has likely changed. Only issue with HSS columns is that the connections tend to be more expensive and that with some facilities, because they allow a thinner wall section than W shapes, they are more prone to damage. CSA S16 addresses beam-columns in a fairly complicated manner.

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

-Dik

 

[JoshPlumSE]

My question is - can HSS steel members (square hollow sections) be used for exterior columns in steel buildings? If so, why isn't it more common to see this used in structural steel buildings?

Yes, they certainly can be used. The HSS columns tend to be more expensive. Both for the cost of the raw steel and the cost of connections / detailing. So, they tend to be used only when needed.... Biaxial bending, architectural desire, or torsion loading.

Is the design procedure for HSS beam-columns similar to the design procedure for wide flange beam-columns? Are there any things that I should consider before getting into it?

I'd obtain a copy of the AISC design guide for HSS connections. It's just a really good reference with a lot of good design examples. So, rather than re-inventing the wheel, you can use the design procedures and standard connections they talk about in that guide.

 

[dik]

If you are practicing in Canada, CSA S16 should be used as jayrod notes... the procedure is pretty elaborate and HSS shapes are treated in a similar fashion as Class 1 and Class 2 section.

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

-Dik

 

[jayrod12]

There used to be a book called Hollow Structural Sections Connections and Trusses that was put out by the CISC, however it has been discontinued. Luckily, the CISC was feeling generous and has posted a scanned pdf of the book for free. It is based off of the S16.1-94 so any actual checks should be using the new code references, however the concepts and examples are a good place to start.

Here's the link to the free download Link

 

[KootK]

1) I think that the prime driver for HSS in these kinds of buildings is just the impact on architectural space. You're often using HSS columns that are 4" to 6" square and either fit nicely within a cold formed stud wall system or relatively unobtrusively beside such a system. An equivalently sized wide flange column will have the following drawbacks:

A) Connecting to wide flange columns smaller than about W10 can be costly for all of the coping etc required.

B) The very small wide flange shapes are not intended to be used as axial member and, as result, tend to be inefficient for use as axial members. Tubes are kind of great torsionally in a way that high Ix/Iy wide flanges are not.

2) You didn't ask about interior columns but those are sometimes made HSS to facilitate racking layouts in big box type structures and for better hygiene in facilities storing food (easier to clean and fewer corners for crap to build up).

3) In my experience, many perimeter columns in these types of buildings will not experience significant transverse (beam) loading. It's often the studwork around the columns that spans between levels and deals with that component of load. Moment frame columns and in-wall braces will often see meaningful transverse load of course.

 

[dik]

Still see a lot of HSS columns used for the interior columns and W sections used for the exterior (in the stiff direction). As jayrod notes... there are substantial revisions to S16 referenced in the CISC publication and the current one.

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

-Dik

 

[EV11]

Thanks everyone for the information and guidance, really appreciated!

 

[JLNJ]

You can also hide an HSS completely inside a CMU wall, if the geometry calls for it.

 

[dik]

paint it to look like concrete?

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

-Dik

 

[dik]

Does anyone have an Excel spreadsheet that accomplishes that that they would like to share?

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

-Dik

 

[EV11]

Thank you for all the responses.

The only uncertainty that I encountered when going through the standard beam-column design process is regarding out-of-plane stability (i.e., lateral torsional buckling). My question would be - can hollow sections (circular, square, rectangular) be subject to lateral torsional buckling?

With wide flange sections, there are design criterion that must be checked for out-of-plane stability of columns, do we disregard this for hollow sections? I was having difficulty finding information on the warping constant for hollow sections, logically it would make sense that the constant would be zero or negligible, I just wanted to make sure I am not overlooking something.

Thank you.

 

[dik]

LTS shouldn't be an issue with HSS sections.

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

-Dik