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Re: Pier ties per 1921.4.4.1 UBC

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Dear Mr. Fruit:

I have some related questions regarding the transverse tie requirements of UBC
1809.5 & 1921.4.
1. Does the Agf'c/10 check apply? Are transverse ties required per 1921.4
regardless of the axial load? 1921.4.1 states the requirements of section
1921.4 apply to frame members (1) resisting earthquake induced forces and (2)
having a factored axial force exceeding Agf'c/10. 

2. What is the definition of a pile? Is a drilled pier a pile? 

3. Are we to expect the engineer to calculate the first point of zero
deflection or point of counterflexure? 
Geotechnical investigations recommending pier & grade beam foundations do not
generally provide sufficient data to determine the point at which fixity is
actually developed in the pier shaft. I'm not sure you can accurately
calculate it given Passive resistance values.  Pile recommendations usually
provide moment profiles.

Thanks in advance,
Tom Jakaby, SE