Deciding criteria for use/not to use bearings in footbridge 1

[Er KCJ]

Hello,

I am doing the schematic design of 36 meter long steel and RCC composite footbridge with a central pier and end supports. The region is seismically active (PGA 0.4g) and maximum temperature change is about 36 deg C. I need advice on how to decide whether any type of bearings are required to be put between the deck and the pier / end supports. Is there any "deciding criteria" given in the European codes for this?

 

[BridgeSmith]

You're going to need some kind of bearings at the pier and the abutments. The pier bearings will need to accommodate rotation at a minimum. The abutment bearings, (or in the case of a fully integral abutment, the abutment itself), at a minimum, will need to accommodate rotation and longitudinal translation due to temperature-induced expansion and contraction of the superstructure. The forces due to the design seismic event will also need to be accommodated by movement at the bearings, carried to through the substructures, or accommodated by elastic or plastic deformation of the substructures.

Reinforced elastomeric bearings (typically reinforced with steel shims or fiberglass layers) are the go-to type of bearings for bridges, especially those where moderate seismic loads need to be mitigated.

 

[Er KCJ]

Thanks a lot for your input! Is there any reference document (book or code) that provides guidelines for selection and design of footbridge bearings?

 

[BridgeSmith]

The AASHTO LRFD bridge design spec has selection criteria and design guidelines/requirements for bridges, that are applicable to pedestrian bridges. I haven't looked at it, but the AASHTO pedestrian bridge design spec probably has guidance more specific to pedestrian bridge bearings.

If you're designing to the Eurocode, you'll need that for design, and I would expect it has guidance on selection criteria, as well.

 

[Er KCJ]

Perfect, thanks once again for your response. I'll look into AASHTO and Eurocode for the information.