IBC09 1810.3.13
IBC09 1810.3.13
(OP)
I have a deep foundation job, and we're driving HP shapes with concrete pile caps. I have some isolated pile caps with no structural slab. This job is designed using the IBC09, and I have a seismic design category "C".
Seection 1810.3.13 Seismic Ties states individual deep foundations shall be interconnected by ties. And it then explains the forces to design for.
However, it is not explicitly clear on the direction of the ties. Are ties to be placed in each of the principle orthogonal directions? Is one tie to each pile cap sufficient?
I already have designed my HP shapes to the criteria in 1810.3.5.3, and am a bit confused by the additional rather unclear design criteria in 1810.3.13.
Any help or clarification anyone has used on 1810.3.13 would be greatly appreciated.
Thank you.
Seection 1810.3.13 Seismic Ties states individual deep foundations shall be interconnected by ties. And it then explains the forces to design for.
However, it is not explicitly clear on the direction of the ties. Are ties to be placed in each of the principle orthogonal directions? Is one tie to each pile cap sufficient?
I already have designed my HP shapes to the criteria in 1810.3.5.3, and am a bit confused by the additional rather unclear design criteria in 1810.3.13.
Any help or clarification anyone has used on 1810.3.13 would be greatly appreciated.
Thank you.






RE: IBC09 1810.3.13
As an additional warning, if you do design a tie to take side bending (in order to resist the calculated lateral force), make sure it is stiff enough to exclude plastic deformation on your pile.
RE: IBC09 1810.3.13
RE: IBC09 1810.3.13
As an aside, the code seems to restrict the use of ties to only tension or compression recognizing the inherent flexibility of a lateral beam.
RE: IBC09 1810.3.13
A common practice in some multistory buildings is to have major columns that run the full height of the building adjacent to smaller columns in the basement that support only the first floor slab. The coefficient applies to the heaviest column load.
Alternate methods of tying foundations together are permitted (such as using a properly reinforced floor slab that can take both tension and compression). Lateral soil pressure on pile caps is not a recommended method because the motion is imparted from soil to structure (not inversely as is commonly assumed), and if the soil is soft enough to require piles, little reliance can be placed on soft-soil passive pressure to restrain relative displacement under dynamic conditions.
If piles are to support structures in the air or over water (such as in a wharf or pier), batter piles may be required to provide stability or the piles may be required to provide bending capacity for lateral stability. It is up to the foundation engineer to determine the fluidity or viscosity of the soil and the point where lateral buckling support to the pile can be provided (that is, the point where the flow of the soil around the piles may be negligible).
RE: IBC09 1810.3.13
RE: IBC09 1810.3.13
Based on ground motion data from Taiwan and others, ground motion at a single building is not uniform, so despite what we like to think of as "ground motion" there is actually a set of ground motions (plural) that are not 100% in phase, so interconnectivity of the foundation is necessary.