Expansion/fixed bearing locations for single span bridge

[bridgeman8]

I'm designing a single span bridge with elastomeric bearings. End bent 1 is higher in elevation than end bent 2. Which end bent should use expansion bearings and which end bent should use fixed bearings? I think I remember reading that there was an advantage to using fixed bearings at the lower end bent, but I can't remember the reasoning or the source. I would appreciate any feedback you may have. Thanks!

 

[rowe]

I don't know if there is a preferred location for the expansion bearing, however, there seems to be a trend toward "jointless" single span bridges.

Perhaps you could eliminate the expansion bearing altogether if your end bents are designed to allow movement (i.e. single row of piles). Good luck.

 

[crossframe]

Typically the expansion joint is placed at the uphill end. The reasoning once explained to me is that the bridge is forced to push itself uphill when it expands, rather than having the weight of the bridge continually "pull" downhill.

An additional benefit to this arrangement is that it should help prevent runoff from reaching and deteriorating the bearings. The drainage may be collected/diverted off the roadway prior to reaching the expansion joint. The runoff on the bridge deck itself will then pass over the fixed (and closed) downhill end.

 

[letrab]

I thought the advantage of elastomeric bearings were that it could accomodate the movement of the deck within itself.
For the abutments itself it would seem that having the deck weight pushing into the soil behind it would be a better solution than pulling it away from the soil as crossframe stated.

 

[koodi]

Go jointless,
The trend has been occuring since about 1940.

The downside is the that people don't like to see cracks.