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Columns - HSS or WF

Columns - HSS or WF

Columns - HSS or WF

(OP)
What are most of you specifying for general steel framed buildings - primarily industrial/warehouse types?

We generally see a lot of wide flange columns used in these kinds of buildings but when you look at the relative weight-stiffness and weight-strength ratios, the tubes look very good.

But if so, why do we see so many WF columns used?

 

RE: Columns - HSS or WF

I prefer to use tubes in cases like this.  Unbraced lengths are the same for all sides, so utilizing a sysmetric member makes sense to me.  

I just complete a buildin of this type, but used WF columns.  The original drawings showed HSS, but the owner said "tubes are expensive".  No convincing him otherwise, so we went to the heavier WF section.  

So I think that HSS members suffer from a legacy of greated expense in production and fabrication.  These costs have come down, but the preception persists.

RE: Columns - HSS or WF

Used to them....connections are easier.
Plus, industrial buildings & warehouses are usually made up of a series of bents or frames with loading primarily resisted by the strong axis of the frame and bracing in the opposite direction.
In other words, WF's put the steel where you need it.  

RE: Columns - HSS or WF

Agree with Toad.  If you use HSS columns in a moment frame, I always worry about bending that face of the HSS.  That is where the WF's have an advantage.

JWB

RE: Columns - HSS or WF

If you are working on a State project which requires domestic steel or a LEED project where you want to get the steel from within 500 miles, tubes may not be the way to go. Many are rolled in Canada.

  

RE: Columns - HSS or WF

To clarify my position.  The buildings using HSS columns use pre-cast concrete, tilt walls or CMU as shear walls on the exterior for later loads.  The columns are interior and taking gavity loads only.

I typically do not use HSS members in moment frames, but they do work well in braced frames.

RE: Columns - HSS or WF

JAE - For industrial applications where long term corrosion is a real possibility we used WF sections to make monitoring of section thickness easier. If corrosion is not a consideration, of course that reason goes away.

www.SlideRuleEra.net idea
www.VacuumTubeEra.net r2d2

RE: Columns - HSS or WF

We usually use HSS sections in areas were connections is not that large of a concern.  If the connections are complex, we will use WF sections as I feel the connections are easier to make.  

Also, as stated above, I worry about HSS moment connections and the side wall of the column.

RE: Columns - HSS or WF

Easier detailing and longer record of possible connections with WF sections.

Pre-qualified weld issues in detailing.

Tubes are more suited for columns than beams, but WF's are good for both.

Tubes used to be more expensive and less available at times in certain sizes and grades.

Mike McCann
MMC Engineering

 

RE: Columns - HSS or WF

I had an issue that msquared48 metioned of the per pound price of steel for HSS being much higher than wide flanges.  Rectangle being the highest per pound.

It was enough for us to go from HSS columns to WF columns

RE: Columns - HSS or WF

Also, our nemesis, Architects, prefer tubes in general over WF's when exposed.  It is a fact that Architects like to expose things.  

I guess it's because they are standing there with their mouth open, closely mimicking the shape of the tube sections?

Mike McCann
MMC Engineering

 

RE: Columns - HSS or WF

JAE... I try for continuous construction with the beams framing over the tops of HSS columns... least costly for warehouse type of structures and often use W shapes at the ends (walls) for lateral.

Dik

RE: Columns - HSS or WF

Use WF shapes for columns.  Connection design with HSS columns in braced frames and moment frames is more difficult and more expensive to fabricate.  For simple framing, shear only beams, HSS columns are fine provided the wall thickness is sufficient for face welded shear plates.  

The fabrication of cutting, slotting, and re-welding of HSS columns is labor intensive and expensive for fabricators.  Expecially when connections are orthogonal.  Wide flange columns are generally beam line items, with cutting and drilling by CNC.  The addition of stiffeners and web reinforcement, can be costly, but can also be off-set by column weight selection.  This fabrication cost and additional material cost does not make HSS columns an equal alternative to WF columns.   

http://www.FerrellEngineering.com

RE: Columns - HSS or WF

M^2-
The architect comments are making me laugh out loud.

also, I have worked on power jobs where HSS was forbidden unless all kinds of fabrication requirements were met, namely, all ends of exposed tubes had to be sealed with cap plates and welds for fear of coal dust accumulating and.... KA-F^&%$'N BOOM!
But, once the ends were "sealed" any possible moisture accumulation inside could be lead to other problems as we have seen in other posts with water freezing inside HSS.

For center columns in warehouses or Home Depot/Lowes/Wallbillies, HSS is probably the best choice.

RE: Columns - HSS or WF

A simple cap plate and base plate fillet welded to the the top and bottom of the HSS plate with 4 bolt holes... Lateral taken by end columns and girts to roof diaphragm into X-bracing... slikker than...

RE: Columns - HSS or WF

Cap plate and baseplate, is the simplest case for HSS columns.  My comments were primarily concerning multi story construction.  Where connections to HSS columns occur at intermediate levels, and require thru-plates or stiffeners.  The HSS walls may require slots and cuts in length (which require CJP repairs).  Bracing connections have increased eccentricity, which require additional bolts and connection size.  Cruciform conditions may require weldments which are concealed within the HSS, and require cutting and repair of the HSS.   

http://www.FerrellEngineering.com

RE: Columns - HSS or WF

For axial only members, tubes.
For columns subject to bending, WF.

RE: Columns - HSS or WF

(OP)
hokie66,
the tubes tend to have larger I, S, and Z values (per pound).  That is the argument in favor of tubes.

Why "buy" WF shapes almost twice as large to get the same stiffness at half the weight?

 

RE: Columns - HSS or WF

JAE,
But that is the case in only one direction, right?  I suppose it depends on whether you are comparing the tubes to relatively square column sections or beam shaped sections.

RE: Columns - HSS or WF

(OP)
The argument put at me is that even when comparing strong axis bending the tubes are better per pound.

I'll spot check a few shapes tomorrow and see.

 

RE: Columns - HSS or WF

I think that is correct if you compare a square tube with a square WF, but with a "beam shaped" WF used as a column, not so.

RE: Columns - HSS or WF

HSS sections are more expensive per pound.

Brad  

RE: Columns - HSS or WF

The trade off is not even.  The material, fabrication, and connections cost more for HSS columns, even if the column weighs less.   

http://www.FerrellEngineering.com

RE: Columns - HSS or WF

Multistory is a different can of worms... HSS come into their own when column height exceeds 10' or 12'... and, I agree, that for multistorey stuff that WF is generally better for ease of connections.
Brad...
Cost per pound is just a little higher unless you are looking at unusual section sizes and the steel has to be 'warehoused' sourced in which case the cost for HSS is markedly higher.

Dik

RE: Columns - HSS or WF

dik, at one time HSS used to be around $.5/lb compared to $0.35/lb for rolled sections in my area.  The fab costs always seem to be more for HSS too.  I have not priced any lately.  Most of the time the Arch never wants things sticking out of his 6" walls, so HSS usually works best.  I am talking two/three stories.

Brad

RE: Columns - HSS or WF

I got complaints on the cost of a 2 story jail that was cost estimated prior to bidding where I had specified HSS columns instead of WF about 5 years ago. We switched to WF and saved a lot on steel cost, I have since left it to the architect to decide if they really want HSS on any building or else I suggest using WF. It may not always be the case on cost depending on the size of columns you are comparing. I understand some HSS shapes are more expensive than others.  

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