Cost of reinforcing bar vs. HSS?

[AnimusVox]

Hey everyone,

(I'm an EIT) In my line of work I'm often given a choice of specifying HSS or steel bars (mostly to assist with strong-axis flexural capacity).

HSS are more efficient, but my question are the costs of specifying one over the other. Can you always assume that lower weight (cross-sectional area) = lower cost?

Thanks!

 

[Shotzie]

Using weight to dictate cost decisions is a good place to start, but another important factor is steel shop availability of material. If they have a lot of HSS in stock in the size you need it may be cheaper than having to order thick bars. It's worth picking up the phone and contacting a steel supplier in your area (potentially one that your company does business with) to pose the question, with specific sizes and quantities to tell them.

 

[BadgerPE]

Are we talking concrete reinforcing? Or are you discussing adding steel bars to structural shapes (presumably WF) to increase the bending capacity?

 

[AnimusVox]

To answer your question BadgerPE, I'm reinforcing vertical mullions in aluminum curtainwall & storefront glazing systems (which are usually controlled by deflection).

EDIT: Also, we deal with projects all over the country (I'm usually working in the southeast U.S.), so perhaps contacting a couple of steel fabricators in that region and see if they have some common shapes that they prefer

 

[BadgerPE]

Ok, I was way off with trying to understand what you were saying. More information in your original post would've been helpful!

By weight, HSS is ~30% more expensive that WF sections. I assume that this number would even be larger than plate. However, it is likely that you will use significantly more plate steel to achieve the same results as an HSS. The reinforced mullions I have seen in the past use C-sections. Cheaper than HSS, but the benefit of flanges for bending.

 

[NorthCivil]

The problem with flat plates within hollow aluminium sections, is how do you fasten it to the aluminium to keep the plate from buckling within the hollow aluminium section? A snug fitting HSS doesn't present the same problem, and is always the better solution.

The constructability issue is much more important that the small cost issue, and that should be driving the decision. Most glass contractors aren't professional steel workers. For any screwed connections, they drill and tap the steel with a huge bag of drill bits that are constantly dulling and breaking , lots of man hours , and screwed connections that fail on installation, as the screw snaps or the head breaks (the contractor may or may not inform you of this)

Without a doubt, the best specification is the one with the least connections between the aluminium and the steel.