Expansion plus movement joint

[haynewp]

If you have a joint between a new and existing building that will be serving as both an thermal expansion and movement joint for drift, should the maximum of these 2 movements be added together?

I think I would take the maximum thermal movement say 1" for each building and add to that the seismic drift say 3" for each building for a total of an 8" joint (since I don't know how hot or cold it will be when an earthquake hits). Do you think this is overkill?

 

[flamby]

8" is theoretically correct. You can reduce it by say 1/8" hoping that peak earthquake will not strike on the peak days of summer but that is unsubstantiated argument with very little gain.

Ciao.

 

[haynewp]

I think the joint width should be based on the addition of 3 factors:

thermal movement, drift, and diaphragm deflection relative to drift.