Elastomeric bearing

[Sahil_Eng]

Hi All, am designing a 60ft long HSS beam (supporting some architectural feature) spanning between two towers.
One end of the beam will be connected using an Embed plate to the conc. and beam welded to the embed. On the other end of the beam I want to give a Sliding connection so that the beam doesn't attract any seismic forces when the towers move. The anticipated movement at the beam locations is around 2 inch.
I am planning to give a steel corbel connected to concrete with embed plate and the HSS seats on the corbel with the bearing pad.
Do you think an elastomeric bearing pad will be a good option and the best way to connect the HSS to bearing pad and pad to corbel.
Thanks for your responses.

 

[BridgeSmith]

To accommodate 2" of movement with an elastomeric bearing, you'll probably need one a couple inches high, at least, unless you incorporate a sliding surface, such as a PTFE sheet mated to a polished stainless steel plate. A fiberglass or steel reinforced elastomeric bearing should work either way you go.

For bridge bearings, we typically use anchor bolts through a slotted sole plate to restrain the members from excessive movement.

The other option is to bond the elastomeric pad to steel plates on the top and bottom, and bolt those plates to the bearing seat and the beam.

 

[dvd]

A couple of references that I have kept and may be of interest - #1

 

[dvd]

#2

 

[PMR06]

I have used slide bearings from Con-Serv many times. You can layout custom bearing pads to about any shape, include bolt holes, slots, etc. They have a lot of information on their website, and their staff is very easy to coordinate with.

https://con-servinc.com/con-slide-bearings-type-csa-csb/

 

[cliff234]

2” is not much seismic movement. Does this movement account for the buildings moving away or towards each other (out of synch) during an earthquake? Check that none of the 2” movement capability is used to accommodate the many construction tolerances. There will be tolerances in the as-built locations of the towers at each end, and there will be tolerances in the locations of the supports on the towers. The 2” dimension will not be enough to accommodate those tolerances. Likewise, you’ll need to consider thermal expansion and contraction of the HSS if it’s in an unheated space or is exposed to sunlight. Is it your intention allow the HSS to slide at one end and pivot about the other end? If so, detail the connections accordingly. I would not recommend welding the HSS at one end. A welded connection will not allow the HSS to pivot about the connection at the pinned end. I would also allow a bit more slot length than what you calculate. If the design earthquake ever occurs, you don’t want the connections to “bottom out” and be loaded in shear as the towers pull away from or move towards each other, because the connections will most likely fail.

There are a number of Teflon slide bearing manufacturers that have good details for slide bearing connections. Search online for them.