Bearing Pads

[ron9876]

I have a condition where I have a heavily loaded concrete retaining/basement wall which bears against the vertical surface of a concrete beam/slab. I want to place a bearing pad along the length of the wall (about 60'). The applied service load is 8.2K/Ft. It has been a long time since I sized a pad for this condition.

Will a 3/8" thick x 8" wide x continuous fiber reinforced neoprene bearing pad with a hardness of 80 work or is it an overkill?

 

[graybeach]

You might want to consider a smaller, thicker, softer, unreinforced pad. The pad you describe will be very hard. It will not deform and spread the load evenly.

 

[BridgeSmith]

I agree w/ graybeach. A plain elastomeric pad (neoprene or natural rubber) similar to what we use for bearing pads for bridge girders should work well. We typically use 50 hardness elastomer at 1/2" thick, which would carry the 8.2 k/ft easily at 8" wide and would conform to the surface much better than a reinforced pad.

The LRFD Bridge Design specs give a service load compression limit of 0.8 ksi for PEP and FGP, so to answer your question - yes, 3/8" x 8" FGP would be major overkill for that loading.

 

[rscassar]

I have always used manufacturers' specifications when it comes to allowable working loads for bearing pads. The supplier should also have some test certificates to support their specifications.

If we are comparing this application to that of a bridge girder, do you need to consider replacement of the bearing pad after a certain amount of time (say 50 years)?

 

[BridgeSmith]

You are correct about using the working loads from the manufacturer, kikflip. I gave those numbers for perspective only, to show that the plain elastomeric pads are generally more than adequate for the proposed loading.

As to replacement, we only consider fatigue for the steel shims in steel reinforced bearings. A PEP should not have a fatigue problem, and there are not any degradation problems that I am aware of from prolonged exposure to concrete, steel or sunlight. If there are other environmental concerns at the site, those should be addressed with the manufacturer.

 

[ron9876]

Thanks for the input.