Footing seismic ties and code interpretation

[structengineer]

I am working with the 1999 Standard building code and want to know what others intepretation of the code is in regards to footing seimic ties. Paragraph 1804.5.3 states that individual spread footings bearing on soil profile type S2, S3, or S4 and assigned to Seismic Design Category D or E, shall be interconnected by ties.

Does this mean all the footings need tied together or just at the footings where moment frames, etc. are located?

 

[JAE]

Usually those code provisions apply to all the footings.
The idea is to prohibit lateral spreading of footings during a seismic event where the columns would be deflected and large Pdelta forces would develop.