Uneven Beam Camber When Loaded 1

[Ghk505]

I recently was on a bridge project where the bridge was completed in two phases. The bridge used inverted t beams and spans were 50’ long. The construction joint was not on center line of bridge but the last beam before. After pouring the 6” deck on the second phase you could see that the first beam by the construction joint had more camber left in it than all of the other beams. What effect will this have on the bridge.

 

[Lomarandil]

Structurally, it will have essentially no effect on a CIP bridge deck (assuming typical girder spacings). Is the camber significant enough to affect rideability?

 

[Ghk505]

Structurally, it will have essentially no effect on a CIP bridge deck (assuming typical girder spacings). Is the camber significant enough to affect rideability?

Crown looked good on top of deck as well as 2%deck slope, so no effect on top of bridge. The girder spacings were all fine, none more than they were supposed to be. Might be caused where the construction joint was put? Project engineer said it’s better than too little camber, but it still looks weird having one girder with more camber than the rest. Thanks

 

[Lomarandil]

Crown looked good on top of deck as well as 2%deck slope, so no effect on top of bridge. The girder spacings were all fine, none more than they were supposed to be. Might be caused where the construction joint was put? Project engineer said it’s better than too little camber, but it still looks weird having one girder with more camber than the rest. Thanks

Oh, the effect is entirely sensical:

The girders were presumably uniformly cambered, without consideration of the deck placement sequence.

The girder directly under the joint was originally loaded with only half of it's tributary width of wet concrete. As such, it deflected downward less than the adjacent girders.

While the remaining deck concrete was placed in the later stage, that wet concrete weight was then applied to a composite girder (connected to the previously cured deck), which is notably stiffer against vertical deflection. As such, that specific girder saw less total vertical deflection due to the concrete placed in two stages.