Pack Rust on Steel Bridges 1

[bridgebuster]

I'm working on a bridge rehabilitation project for a viaduct constructed in the late 40's/early 50's. Some built up floorbeams - photos attached (one photo is an extreme case) - have been affected by pack rust/rust pact/impacted corrosion – call it what you will.

The client is looking for specific remedies to this problem. Their opinion is that the traditional remedy of blast cleaning and painting won't work. In the 80's I worked on a project in Ohio with the same problem. The ODOT spec, in addition to blast cleaning and painting, called for the installation of an acrylic caulk between the steel plies prior to painting.

I would like to know if others have any successful methods of dealing with this, in terms of a coating or sealant.(From a structural standpoint there are locations where we may have to remove rivets; then remove the rust; heat straighten; then install bolts.) There's not a lot of information out there; although I came across differing opinions. One article recommended "meticulous cleaning" (that's not going to happen) followed by an acid neutralizing paint. Another said water blasting is the worst thing since it will only entrap the water

 

[bridgebuster]

Attached is a drawing that provides guidance on rivet replacement.

 

[limey1]

This question may be mute, but I do make a habit of asking what may appear obvious.
After any prep work has been carried out, is there any testing done to check the integrity of the plates etc (Example U/T) as far as load rating capability?
I have no experience in this field and was just curious.

Cheers

 

[bridgebuster]

The engineer in charge of the construction will usually inspect an area to be repaired in order to determine the repair limits. I've never seen anything other than visual inspection. The other methods are typically used during bridge inspection.

On a painting contract, you have to hope the inspector is diligent, and if he sees something he3'll say something.

In NY all fracture critical and fatigue prone details receive 100% hands-on inspection during the biennial inspection. I've also done bridge inspections of some major long span structures on which mag-particle and U/T testing was performed on certain fatigue prone details

 

[limey1]

Thanks for answering my curiosity bridgebuster (Apt name)

 

[bridgebuster]

no problem

 

[hokie66]

bridgebuster,
I read those notes to require the replacement of all rivets which are stretched by the pack rust...Note 7.

 

[bridgebuster]

kokie,

Although it doesn't explicity state it; I read it that way also.

 

[hokie66]

I imagine that in the photo you posted, there would be no rivet metal intact. They would either be fractured or severely necked.

 

[bridgebuster]

We're still a year or more from construction; it'll be interesting to see what's found. I appreciate your interest.