Ties of piles in seismic zones

[J1D]

In NBC (National Building Code of Canada) there is a provision saying "Except in velocity-related seismic Zone 0, individual pile footings, drilled piers and caissons shall be interconnected by ties in not less than 2 directions". This seems to be a strict requirement. I don't know if UBC has similar provisions.

 

[sundale]

The 2003 IBC in Chapter 18 talks about this; it sounds quite similar.

Basically, you have to interconnect pile foundations for larger commercial buildings if they are not in a pier cap with at least 3 piles (IBC1808.2.5).

Note that piers are not piles in the IBC; piles have L/D>12.

IBC1808.2.23 talks at length about seismic tie forces and detailing requirements for seismic design category "C" and worse...

Hope this helps,
Eric

 

[BigHarvey]

We have the same requirements in France.

 

[J1D]

Thanks for the info. NBC 2005 revises the requirement to be conditional, even for the areas requiring seismic design. Whether the ties are needed depends on the spectral response acceleration, soil condition and other factors. For piles (piers, caissons) in soft soils more likely the ties are required.