Rail bridge bearing replacement

[MichSt]

I am working on a rail bridge bearing replacement project and will be attaching new steel sole plates to the existing 1890’s riveted steel plate girders as part of the work. I plan to attach using countersunk high strength bolts since the sloe plate will sit on new electrometric bearings. Welding was not considered due to possible poor weldability of the existing steel.

What other/better options are there for this connection?

 

[bridgebuster]

There's not much else you can do unless you want to get into some messy details involing Z-shaped bars.

I assume your not countersinking the bottom flange of the plate girder.

 

[MichSt]

Correct, the sole plate would be countersunk, which may require a thicker plate than needed otherwise.

I think this is the way to go but wanted to check to see if there were other more obvious options that I was missing.

 

[DRC1]

Another option woul be to drill and tap the sole plate and bolt down w/ a std hex head bolt from the top. I would use a plate on top of the flange. This will distrbute the load so if the surface is badly pitted or if there is localized cracking, it will not effect the connection. Plus bolting down with hex heads should be easier than bolting up with countersinks.

 

[MichSt]

Thanks DRC1,

I spoke with a few others in my company and that is the option I’m going with. Not only will it be easier to install as you said, but there will be a plate welded to the bottom of the sole plate that’s part of a TFE slide bearing assembly. This plate would have to be field welded overhead if countersunk bolts were used, which is no good. With the tapped holes this plate can be shop welded.

You mention using a top plate to distribute the load on the existing top flange, which is a good comment, but wouldn’t this top plate only be loaded if the bolts are in tension?? I don’t have any uplift on the bearings. The only tension the bolts will see is after the plate is installed and the girder is still jacked off the masonry plate. This should be a negligible load. Am I missing something?

 

[Dinosaur]

Can a laminated elastomeric pad carry the horizontal loads perscribed in the AREMA?

 

[DRC1]

The top plate is not really for any calculated load. I would use it just because the existing steel may not be in the best of shape. As trains move across the bridge, the beam flange works slightly. Also when the bearings are tightened, they induce tension in the connection. Any existing defects or cracking can cause some tearing which in time may loosen the bolt. This way if there is a crack, it is clamped. Its just that you can never be sure of the actual condition of older bridges.