Corrosion in Steel Piles 2

[JohnCE920]

I appreciate anyone's help on this. I'm looking at a 20yr old bridge abutment that has steel piles inside corrugated pipes to help with expansion. Upon inspecting this abutment, I found that water had made its way into the pipes and the pile is partially submerged in water. I assume this drains slowly and we have a section with wet/dry cycles.

The only way I can think to measure the section loss is to dig the pile out to the length of the corrugated pipes. Naturally this is invasive and expensive. Does anyone here know where I can find expected corrosion rates for this situation assuming fresh water? I want to be able to estimate the loss to see if we're close to having structural issues or if with reasonable and conservative assumptions, I can say this is OK (while removing the water source).

Thanks again

 

[SlideRuleEra]

See "Corrosion of Steel Piling in Soil" by the US National Bureau of Standards. The data includes the wet/dry area.

http://www.SlideRuleEra.net

 

[HTURKAK]

I think the corrugated pipe depth should be in the range of several feet, and the pile buried in the soil below the corrugated pipe is in submerged condition. The below snap from Pile Design and Construction Practice (Tomlinson ). The average corrosion rate should be in the range of 0.02 mm/year.

 

[Agent666]

This might be of use as another data point, it's from the NZ steel code.

 

[JohnCE920]

I appreciate everyone's contribution to this topic. I have some reading to do.

I did manage to find this table in BCSA that has a parallel table with FHWA's Steel Handbook. My thinking was to use category C4. While I don't have salinity in the water coming in, I likely have more dry/wet cycles than just atmospheric conditions.

 

[GC_Hopi]

My experience is that there are many corrosion tables so DOT's have their own. You should check with your client to see if they have a preference. If not recommend one.

For the piles, sounds like you are on the right path. Checking the required capacity assuming some loss of thickness due to corrosion against the demand. You might get lucky and the original designer added some sacrificial thickness.