Expansion Joints and seismic Joints

[VA-Struct-Engr]

Hello all,
I am designing a 10 story steel framed building in the mid-Atlantic region. The building footprint is relatively large and requires an expansion joint. The lateral force resisting system in both segments of the building is the same, i.e. braced frames. I don't necessarily have to have a seismic joint in the building. Building is SDC 'B'. My question is do I need to treat the expansion joint as a seismic joint and size the joint per ASCE 7-16 section 12.12.3 (Structural separation)? Commentary to this section states "Such joints may effectively eliminate irregularities and large force transfers between portions of the building with different dynamic properties".

If I understand this section correctly, since both buildings have the same lateral system, seismic drifts will be similar (may not be exactly same), and the approximate fundamental period of both segments of the building will be same, both buildings will have not have different dynamic properties, hence, I can ignore this provision in sizing the expansion joint.

Please let me know what is the general industry practice. If you can point me to any resources on this topic, I would appreciate it.

Thank you for your responses in advance.

 

[GC_Hopi]

I think best practice is to size the joint per ASCE 7 section 12.12.3 since there is no guarantee the building will sway in the same direction at the same time. It is possible they will both sway toward each and you could have seismic pounding between the buildings

 

[structSU10]

as GC states, even if by the numbers the period / frequencies match the buildings are unlikely to move exactly the same and could sway opposite each other so a joint sized for seismic is appropriate.

 

[phamENG]

I agree with GC and structSU10 - you should design your expansion joint with 12.12.3 in mind. Whether you need the joint to satisfy seismic response requirements or not, you need to consider the possible movements of the building segments during an earthquake.