Welding to Concrete Filled Hollow Steel Sections

[LobstaEata]

I've been taught by mentors long ago, to avoid welding to concrete filled hollow steel sections, especially when the wall of the steel section is thinner than the weld size. The thought is that if you produce enough heat, it will produce a small explosion in the concrete voids, due to expansion of residual water vapor.

Someone in my office is asking about this very subject and wanted to know if this phenomenon can be substantiated by an authoritative article on the subject. I didn't think this would be a problem to find, but am having trouble finding much of anything on the subject.

So, does anyone here have experience with this issue or know of a source that I may point to to either substantiate or refute avaoiding welding to concrete filled hollow sections?

Many thanks.

 

[Guest102023]

Its not the kind of thing that is the subject of 'authoritative papers'.

I don't know but I'll bet that 'someone' has too many university degrees. Beware of bosses who make you jump through unnecessary hoops.

 

[MikeHalloran]

A long time ago, I designed a flight simulator, to be constructed in two different locales. When it came time to dynamically test the 'motion base', the simulated cockpit assembly was not ready, so we simulated its mass and dynamics with four concrete filled HSS sections, primarily attached by asymmetric flanges at the bottom, with welded ears attaching bolted diagonals.

One of the flanges was welded in the wrong orientation. I first proposed cutting through the square tube to rotate it. The (experienced) fabricator/welder refused to attempt it, citing personal danger from liquid metal being propelled by exploding concrete. We talked some more, and were able to save the part by cutting through the flange at the tube periphery, rotating the flange, and rewelding it.



Mike Halloran
Pembroke Pines, FL, USA

 

[connectegr]

I am not aware of any journal or research article concerning this procedure. But, you noted the primary concerns. I have seen several project specifications which prohibit any welding to buckling restrained braces.

http://www.FerrellEngineering.com

 

[dhengr]

I’ve seen conc. explode, at least drastically spall, most likely for the moisture and aggregate expansion reasons you suggest, when heated with a torch. You could have a steam pressure build-up problem in a thin HSS. Maybe you could drill a couple small holes near the weld area as vents. Alternatively, we often weld to embedded plates and the like, don’t we? Some judgement must be made about plate thickness, weld size, heat input, and heat dissipation within the weld plate. I don’t think I’ve ever seen any write-up on the subject, I learned the hard way, and suffered no long term damage, except shock and surprise at the moment.

 

[21121956]

Hello everybody:

LobstaEata, see thread507-290241 and

http://www.millerwelds.com/resource...showthread.php?26706-Welding-an-embedded-pipe

I hope you can enhance your knowledge on this matter.

El que no puede andar, se sienta.

 

[Toddr8541]

Steel roof trusses are welded to steel embeds that are placed in concrete on top of the bond beam of CMU walls. I have seen them done the day after the concrete was in place without any issues. This situation maybe a little different due to the concrete being encapluated in the steel tube. I think if you weld short length welds at a time with some cooling between each one you should be ok.