HSS Sections as Beams 2

[StructuralAddict]

Hi all!
I was just thinking of why don't we "structural engineers" use HSS sections to design steel beams? HSS sections are good in resisting lateral-torsional buckling. So, why we almost always use W-sections for beams? I noticed that in the majority of the building I saw.
Thanks in advance!

 

[jayrod12]

Strength per dollar. Wide flanges are cheaper to roll than HSS shapes of equal strength are to make. Not to mention, in a lot of average framing scenarios, LTB is normally a mott point as the beam ends up being braced somehow. If I have a lack of lateral bracing for compression flanges, I will commonly switch to HSS members.

 

[skeletron]

More difficult to connect to the columns
Thin walls have some disadvantages and unique limit states
Welding attachments (deck, edge angles, etc.) is also a little more precarious because of the thin-wall structure
Availability
Potential for trapped water or the need for weeping holes for galvanized structures



Once you have positive connection to the top flange, you can really defend against LTB quite easily. W-sections may have their peculiar geometric qualities and disadvantages, but are quite well tested and adaptable.


...but I can't recall if I have ever solved that problem yet.

 

[Ron247]

I think they are one of the more expensive per pound of the shapes. They are harder to manufacture than most other shapes. Also they max out at 20" deep.
We do tend to use them more when you cannot laterally braced something but most of my projects are easily braced.

Connections can be tedious at times.

 

[Agent666]

The only time I've seen HSS being a prefered structural section type on an extensive scale was when there was a rather onerous painted corrosion protection system on some long span trusses, the surface area was considerably less for the HSS so it made sense when factoring in the total cost of construction to use HSS where ever we could in the trusses.

 

[Earth314159]

They are less efficient. You have to pay for two very thick webs instead of one thin web. They cost more per lb. Most W-sections have sufficient bracing of the top flange so that lateral-torsional buckling length is minimized or not an issue. However, I still occasionally use them as beams where it makes sense. They are great for beams in the exterior walls of high-end custom houses. You can fit 1.5" of insulation on the cold side of a 4" wide HSS in a 2x6 wall. They are also great from resisting the out-of-plane wind loads at the same time as acting as a header. You can even build trusses inside the wall where a wall segment cantilevers out or use as a brace frames where wood shear walls are just not good enough.

 

[Iasonasx]

They are designed to be used mainly as axially loaded members, not flexural members, but sure, if it serves you better in a specific scenario, you can certainly use them.