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ASCE 7 Foundation Ties SDC D

ASCE 7 Foundation Ties SDC D

ASCE 7 Foundation Ties SDC D

(OP)
Foundation ties area required in high seismic to restrain top of shaft foundations from rotation or lateral movement. I intrepret this to mean not only shafts supporting columns of LFRS but any columns that may just be part of a gravity system; do you agree?

Interested in others experience in viability of demonstrating adequate lateral capacity from soil without foundation ties (no slab exists either) for isolated drilled shafts for SDC D?

RE: ASCE 7 Foundation Ties SDC D

That's what I'd do... in a seismic event, you don't even want secondary columns to translate.

Dik

RE: ASCE 7 Foundation Ties SDC D

We had a geotech on a project give an option to excavate 5 or 6 feet around all the pile caps and refill with compacting crushed stone in lieu of ties. I would consult the geotech if similar could be viable at your site with drilled shafts.

RE: ASCE 7 Foundation Ties SDC D

haynewp,

That sounds like a poor excuse for an attempt to circumvent the intention of the requirement.

RE: ASCE 7 Foundation Ties SDC D

Hokie,

I don't know, I'm not a geotech and that is why I suggested consulting with their geotech. But that was an option that was given at that site by that particular geotechnical engineer.

RE: ASCE 7 Foundation Ties SDC D

Hokie,

There are actually provisions that allow for this in IBC Chapter 18 in some instances. Perhaps you should take a look.

RE: ASCE 7 Foundation Ties SDC D

The IBC is not something I have to deal with, so no thanks.

RE: ASCE 7 Foundation Ties SDC D

Every interpretation I've seen has indicated this applies to all deep foundations, not just under LFRS but anything supporting the gravity system as well. Your post only mentions SDC D, but this is required in SDC C too.

IBC allows this to be waved if you have slab present that is used as a tie or if you're in competent rock, hard cohesive soils or very dense granular soils. Assume that's the direction the geotechnical engineer on haynewp's project was going in. My first impression would be you'd need to replace more than just the 5-6 feet around the pile caps , but I'm no geotechnical engineer.

RE: ASCE 7 Foundation Ties SDC D

That was the direction the geotech was going in on that project. There is also an example in the 2012 IBC SEAOC Seismic Design Manual that uses this concept in an example with a site's very dense granular soil and passive pressure.

RE: ASCE 7 Foundation Ties SDC D

(OP)
haynewp - I have those books, which volume/example?

RE: ASCE 7 Foundation Ties SDC D

Volume 1, example 48. I would still involve the geotech before proceeding.

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