Stainless Steel Anchor Rod vs Galvanized Anchor Rod - Pros & Cons 1

[oengineer]

What are the benefits of using a Stainless Steel Anchor Rod vs Galvanized Anchor Rod inside of a Lift Station/Wet Well?

The anchor rod is inside of the Wet Well, connecting the wall to the bottom of the slab (see image):

Initially, to me the benefit of using just a galvanized anchor rod is that I can use a higher strength steel (both yield & tensile strength). But the concern is that just using galvanized anchor rods would not be sufficient to resist corrosion due to the constant exposure the anchor rod would have to resist based on what is inside the wet well.

I am trying to determine the best rout to go regarding this connection. Stainless steel seems to have a much lower available yield & tensile strength. But I am not sure if galvanized steel would endure as long as stainless steel.

Comments/suggestions are appreciated.

 

[PEinc]

Maybe you should have posted this in the Corrosion Engineering forum.

http://www.PeirceEngineering.com

 

[EdStainless]

Over time the galv will be consumed, the SS should stay longer.
Do they say anyplace what stainless grade?
Can you get 2205 or 2101 duplex stainless? These will be much stronger than 304/316 alloys are.
They have better corrosion resistance, better cracking resistance, and they are less likely to gall.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[GC_Hopi]

I would avoid galvanized in this situation. You are practically guaranteed to have standing water in the bottom of your structure over its lifetime not to mention the high moist content in the air and corrosion would be a big concern. I have never seen the arrangement in your snip but could you provide grouted dowels in the wall. You would have to look at the waterstop again but it could fit.

 

[canwesteng]

You can get very strong stainless anchors, basically equivalent to grade 55 carbon steel anchors. I would question why you would need grade 105 (or even grade 55) in this application. Also I wonder if the zinc oxide products don't compromise the passivated layer on the stainless angle shown in your sketch, but also better for the corrosion forum.

 

[JStephen]

Some of the stainless steels have fairly low yield strengths but much higher ultimate strengths, and allowable loads may not be as low as you're thinking. In bolt-sizes, they may be strain-hardened also.
Anyway, I would think installation labor would be 90% of the cost of these, and the cost of the widget itself not so critical.

 

[Settingsun]

Are you actually counting on the full steel strength at that embedment depth?

 

[HTURKAK]

Apparently, this is valve chamber rather than wet well of a P.S. The concrete surface, anchors angle subject to splash and heavy humidity .

The detail imo, constructive rather than structural requirements . So, the strength of bolts should not be an issue.

My suggestion will be, if the angle L 6X4 is stainless steel, the anchors SHALL ALSO BE ss. or, alternatively choose galvanized angle together with galvanized rods in this case, epoxy grout extending to 300 mm wall ht will be helpful for protection.

 

[Rabbit12]

Use stainless steel. If it's going to be submerged or subjected to standing water frequently go with 316. If just humid you can probably get away with 304.

 

[oengineer]

Based on the comments, it appears stainless steel is the way to go.

What would be the most common stainless steel ASTM designation to call out in order to obtain a grade 55 or 105?

Also, would anyone have an alternative way to connect a cast-in-place bottom slab to a Precast circular riser wall (other than the angle connection shown in the image in the initial post)?

 

[canwesteng]

A193, B7 or B8

 

[GC_Hopi]

A few options 1) You can do dowels or pins as they are called. 2) Do a groove or step around the perimeter for the wall to rest in. 3) Post install the dowels after the walls are set and cast a curb around the perimeter.

 

[oengineer]

A few options 1) You can do dowels or pins as they are called. 2) Do a groove or step around the perimeter for the wall to rest in. 3) Post install the dowels after the walls are set and cast a curb around the perimeter.

Do you happen to have any sketches/images of these suggestions you've mentioned?

 

[GC_Hopi]

#1 Shear pin. I dont have image available but mark up should get the idea across. Probably the least common approach

#2 Base slab with step

#2 Base with integral starter wall for step

#3 Base slab with curb/fillet without dowels but you can image drill a hooked dowel into the slab then the hook is in the curb/fillet.

 

[JoelTXCive]

1) Is it a stormwater lift station or a sanitary lift station? (if sanitary, then definitely go stainless steel)

2) Also, It is not recommended to have stainless steel touching galvanized steel in a wet environment. It creates a 'bi-metallic couple' (galvanic reaction)

see research...

https://galvanizeit.org/knowledgebase/article/stainless-steel-in-contact-with-galvanized-steel

Once you commit to stainless anchors, you either need a bond break of some sort; or you need to connect to other stainless steel pieces. I've screwed this up in the past. It's not the end of the world, but you are not supposed to touch stainless to galvanized.

 

[BAretired]

Would it help to move the angle and anchors to the other side of the wall?

BA

 

[oengineer]

1) Is it a stormwater lift station or a sanitary lift station? (if sanitary, then definitely go stainless steel)

2) Also, It is not recommended to have stainless steel touching galvanized steel in a wet environment. It creates a 'bi-metallic couple' (galvanic reaction)
see research...

https://galvanizeit.org/knowledgebase/article/stai...

Once you commit to stainless anchors, you either need a bond break of some sort; or you need to connect to other stainless steel pieces. I've screwed this up in the past. It's not the end of the world, but you are not supposed to touch stainless to galvanized.

I believe that the Lift Station is a sanitary lift station? Based on the comments in this thread, it seems like stainless steel is the way to go.

What do you mean by "bond break"? Could you please provide a link or image?

Would it help to move the angle and anchors to the other side of the wall?

With the way the contractor intends on constructing it (Caisson Method), I do not see how that is possible.

 

[JoelTXCive]

Bond break just means 2 components are not physically allowed to bond together. If the 2 elements are not allowed to touch, then the galvanic reaction can be stopped. This is true of all metals. Copper and steel, aluminum and steel etc...

In this instance, it just means that the stainless steel should not be allowed to touch the galvanized steel. This could be accomplished with neoprene gaskets, or coating one of the elements with a rubberized paint.

 

[oengineer]

A193, B7 or B8

I am seeing that the ASTM A193 B7 is not stainless steel.

It looks like ASTM A193 B8 is stainless steel, but it has a yield & tensile strength of 30 ksi & 75 ksi, respectively.

In order to get a higher strength, it looks like one needs to specify ASTM A193 Grade B8 Class 2 (yield strength of 100 ksi and tensile strength of 125 ksi).

Would a ASTM A193 Grade B8 Class 2 stainless steel rod be somewhat common?

 

[GC_Hopi]

If this is the caisson method, you should dowel in the wall or provide couplers then pour the base slab inside of the caisson. No reason to have a toe on the base slab.