Expansion Bearing 1

[lsmfse]

I've designed a 75' simple span steel bridge with concrete deck.(Bridge is a private access bridge to a residence) Bridge is supported on grade beam and caissons. One end was detailed with base plate with slotted holes to allow for expansion. Contractor did not use slotted hole bearing plate. My concerns are:
1. Based on 40 degree temp. swing, axial load in steel stringer is about 420 kips. Modeled as a column considering P-delta, beam is no good.
2. Calculated length of expansion is only about .25". This seems minimal and yeilding at the support could accomodate the expansion.
Any thoughts or suggestions?

 

[CanyonRat]

I work for 3 state dot's and their policy is no expansion joints unless the bridge is over 300' to 350' long. Now, I design simple span bridges all the time up to 120' to 140' long and have never used expansion joints. These bridges are either on piles or caissons. Our firm designed a 190' simple plate grider span bridge on piles that has no expansion joints (ie all integral). I have, however, designed simple span bridges over 200' with expansion joints.

So, I don't know why you have them in the first place. Look at the long list of bridges without expansion joints that are longer and have been in service for many years and you see no problems.

I think you need to re-think your system. The caissons should give at least a 1/4" and not even design for temperature.

Run LPile or something and see if the caissons fail with a 1/4" deflection...

MikeD

 

[lsmfse]

Canyonrat-That was my gut feeling that enough yeilding would occur at the supports. Thanks for the input.