Light pole tabs on bridges

[tmalik3156]

Good day all.

We are designing semi-circular cantilever tabs to support light poles on the exterior of a bridge. Due to wind action, the light poles – and therefore these tabs – are subjected to significant moments / torsion.

Some DOTs have standard drawings for these tabs. An example from Ontario is shown below.

But we need to see some calculations, so we can understand how these standard detailing resist moments and shears. Then we can adapt / modify the standard designs as needed.

Has anyone here ever designed pole base tab like this? Could anyone kindly share any calculations, or any other standard details that might help us in designing similar members?

Thank you

 

[BridgeSmith]

When we've done this our bump-outs are significantly bigger, and I wasn't directly involved, so I don't know if there were any calculations done. The wind loads on a light pole are relatively small.

That said, if you want to check the support, I would think you'd apply the moment at the base of the pole as a force couple on the anchor bolts, to check the bolt tension and anchor embedment. Then, you'd check the reinforced concrete bending capacity at the outside face of the deck slab and compare to the pole base moment.

 

[tmalik3156]

@BridgeSmith
Thank you for your reply.
The torsion which tends to twist the pole base about bridge transverse axis is a bit tricky to design for.

 

[BridgeSmith]

Other than the shear on the anchor bolts, the torsion can likely be ignored as a negligible loading. If you want to check it, you can apply it as a moment on the tab producing tension on one side of the tab (say the left side) and compression on the other side (the right side), and check it as a reinforced concrete beam oriented horizontally instead of the typical vertical orientation.