Seismic Joint vs. Structural Separation 1

[Despy]

I have an addition to a large church. To simplify the design the new portion of the structure is separated from the existing building by a 1-1/2" joint. We have referred to this on our plans as a "Seismic Joint". This is typical for our office. According to the architect, by using this label the mechanical engineer has to add extensive hardware for all of his pipes/ducts that cross this joint. However, if we refer to the joint as a "Structural Separation" these requirements do not apply.

What is the difference between these two terms?

 

[JAE]

I am confident that whatever term you use to label the joint on your plans has NO affect on how the mechanical engineer must deal with his elements crossing that joint.

You have elected to create two separate structures, each with their own lateral force resisting systems. Each has unique performance characteristics such as their natural period, wind deflection and seismic deflection.

You design your structure and have a maximum seismic deflection in A and also in B. The combined deflection is the gap that you should provide between the buildings. You also have wind deflections between the two buildings.

The mechanical engineer should be notified (by you) of what these deflections are - wind and seismic deflections will be different.

It is up to them to propoerly meet the code and detail accordingly.

 

[Despy]

That is pretty much what I had assumed. I was unaware of any difference, but figured I'd ask the question to see if there was some obscure requirement based on nomenclature.

 

[woodman88]

The problem is that some plan checkers will redflag anything noted "seismic" where a "structural" note will not be redflagged. But as JAE states, both should require the same detailing.

Garth Dreger PE
AZ Phoenix area

 

[VoyageofDiscovery]

Whatever it is, make sure the mechanical engineer has the x,y,z max. relative deflections and rotations to be accommodated as a gas line failure across this joint would surely be detrimental to the structure.

 

[BAretired]

Why not tie the two structures together and avoid the mechanical issue?

BA

 

[engrbon]

Perhaps they can use flexible connections for all the pipes and ducts that will cross this joint...just a thought.

 

[Despy]

The buildings need to be separated because the original structure is a Frankenstein's monster of various additions and renovations. If we connect to it, we have to upgrade the original to meet the seismic requirements of the newest building code. We definitely want to avoid that.

The mechanical engineer was fishing for a way to avoid having to use flexible connectors. They are out of luck since we do need accommodate differential movement.

Thanks for the input.