Weathering steel 6

[CivilEngineerUK]

I have a weathering steel column.

1) How to calculate corrosion after 120 years? Any standards to use?

 

[kingnero]

I'd say in general that's a bad idea. For a numbers of reasons, Ed already pointed out the two most important ones.
In addition, both concrete and steel will wear heavily if there is contact (you have a 20mm gap?). This is for sure not a 120yr solution.
I also dislike the form of the concrete, but I'm by no means a concrete specialist.
The bent plate could probably use the stiffener all the way, but we can't see the entire detail .
Use rollers inside the flanges, to avoid the abrasion. Or change the whole fixation set-up to cast-in plates and use steel-steel contact (but not weathering steel or stainless steel) to accomodate the movement.

Also, what's up with the text on the drawing: "stainless steel" and (S235/S355) ?

 

[CivilEngineerUK]

The figure is just a quick sketch. What do you mean with rollers inside the flanges?

 

[kingnero]

Crude sketch attached.

But I'd still prefer a classic steel-steel expansion joint detail over this, because it probably still requires cast-in contact plates where the rollers run ocer the concrete (I'll let the concrete guys take this one).

 

[Settingsun]

The people who do this at my company just put a thin plastic pad between the dissimilar metals. Concrete direct against the corten steel, though you could put plastic/rubber there if concerned.

 

[CivilEngineerUK]

A classic steel-steel expansion joint, is that the roller joint or another joint type?

 

[kingnero]

That would be a bolted connection with elongated/slotted holes

 

Likely some of the stainless steel whizzes here can add more information.

Weathering steel and stainless steel are perfectly weldable, and galvanic corrosion should not be automatically assumed, it depends on the conditions.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[dik]

They are weldable... maybe not quite perfectly... some minor hiccups.

Dik

 

[CivilEngineerUK]

Which conditions are good / poor for welding stainless steel and weathering steel together?

Furthermore, can cracks occur in weldings between stainless steel and weathering steel as they have different properties?

 

[kingnero]

I don't think in this case, there is any practical way where it can go right.
You have an overlap, probably stitch welded because of deformation, so voids everywhere, the corten ground blank because it has a thick oxide skin, outside conditions (moisture and temperature/differential expansion inducing stresses), ...

I'm sure IM will agree on this, taken into consideration the specific conditions of your setup. If not, I'd be happy to be proven wrong.

 

Weathering steel contains small amounts of alloy and weldability is similar to that of other low alloy steels. 309L is the filler metal of choice. Some of the speculative welding advice on this thread is not helpful.

CivilEngineerUK: if the joint is elevated and drainage is good there should be no long-term issues (although 120 years is extremely long-term; periodic inspections will be necessary). But you are correct to avoid having weathering steel in a sliding joint.



"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[ACtrafficengr]

Is this a highway noise wall in northern climes? The New York State Thruway found the hard way that tire spray will carry deicing salts much further than they anticipated, to the detriment of their A588 bridges. I don't recall exactly, but it was something like >6m up and >20m horizontally from the travel lanes.

My glass has a v/c ratio of 0.5

Maybe the tyranny of Murphy is the penalty for hubris. -

http://xkcd.com/319/

 

ACtrafficengr,
Southern Ontario's Niagara region found the hard way that deicing salts can destroy valuable fruit trees at a distance of much greater than 20m.


"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[songshun]

what grade it is? If you know the grade of material, you can google it and find the answer.

 

[CivilEngineerUK]

The grade is 355

 

[GGedge]

Going back to your original question and assuming you are in the UK (given your name). You could start with Highways England Standard CD361,"Weathering steel for highway structures". Section 6 includes corrosion allowances per exposed surface in the range 0.5 to 1.5 for 120 year design life (typical UK bridge design life), dependent on the service environment. It also includes other requirements regarded as "best practice" in relation to detailing when using weathering steels. Although written essentially for bridges it is more widely used on structures generally. Note the allowances are for corrosion only, not wear due to relative movement of parts.


Cheers

GG

 

US DOT and state DOTs have lots of material online, including many technical reports. For states I would start with PA.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

It's generally a bad idea due to the difference in the metallurgy.

It's done every day. Any potential risks are evaluated on a case by case basis.

Also stainless has different thermal characteristics which makes heating and cooling different leading to cracking.

Always? See above.


"Everyone is entitled to their own opinions, but they are not entitled to their own facts."