Seismic Buffer Rubber, Neoprene or elastomeric material

[tdstructural]

I am designing an upgrade to an existing Boiler support frame. The boiler is approximately 65 feet tall and in plan view it is appx 20' x 17'. It is located in South America in a high seismic region.

The original lateral resisting system is Structural Steel Braced Frames. The load path goes thru the boiler walls into the buckstays, then short WF members are welded to the buckstays and they extend into a detail they call "Seismic Buffer". Those short members are fixed to the buckstay and free to move both vertically (boiler heat expansion) and laterally perpendicular to the brace frames. The only force that is transferred is parallel force to the brace frame.

They used some type of rubber pad between the horizontal WF and the brace frame. They alternate "rubber" like material appx 1-1/2" thick with 1/4" steel plate and use (4) "rubber" pads on each side of the horizontal WF beam. Please see the link for a picture to help clarify.

I think it might be to reduce vibration/noise. I see no other reason for this massive amount of material.

Where can I find specs for this type of product so I can design it for the correct compression forces? What is the name of this product? Am I right that they did this to reduce vibration between the boiler and the structural steel braced frames?

Any help would be appreciated.

 

[hokie66]

It would be rubber, either natural rubber or neoprene rubber. Serves both operational dynamic and seismic functions. Google is your friend for finding properties, or for finding suppliers with information.

 

[MikeHalloran]

I'm kind of fuzzy on how that assembly is intended to work.
Rubber is normally stressed in shear, which appears to be not the case here.



Mike Halloran
Pembroke Pines, FL, USA

 

[hokie66]

Why would you say that, Mike? Whole buildings are supported on base isolation rubber bearings, and parts of buildings e.g. performance halls, are supported on rubber bearings for noise and vibration isolation.

 

[MikeHalloran]

Yeah, they are, on rubber/steel sandwiches like in the photo, but in a different orientation.

What the rubber is intended to do in the case of a building support is provide flexibility to lateral/horizontal movement, by shearing. The sandwich is basically incompressible in the usual building's vertical direction, so it does a good job of supporting the building.

The assembly in the photo appears to have two rubber/steel sandwiches trapped in a direction in which they do not ordinarily yield, with what appear to be through-bolts and smaller stacks outboard.



Mike Halloran
Pembroke Pines, FL, USA