PIle to cap connection high seismic 3

[haynewp]

I have a pinned assumption of pile to cap, the auger piles extend 6" into the bottom of the cap. The piles have uplift and the longitudinal pile reinforcing is being extended into the cap to develop the bars.

Are these longitudinal bars extending into the cap required to have closed ties around them within the pile cap itself? This is a high seismic area.

 

[SlideRuleEra]

haynewp - The short answer to the requirement of closed ties around the longitudinal bars within a pile cap is "No, not required (by codes)". However, the entire concept of how a pile SHOULD be connected to a pile cap in a high seismic area is rapidly changing based on (poor) pile-to-pile cap performance in major earthquakes.

There is growing evidence (again, for high seismic loading) that the piling themselves should project into the cap substantially more than the long accepted 4" to 6". Various agencies are adopting requirement for additional embedment. One that I am familiar with is the South Carolina DOT (parts of SC are at risk of significant seismic events). Here is a recent (November 2012) update to their Bridge Design Manual that requires more embedment:

http://www.scdot.org/doing/technicalPDFs/bridgeMemos/DM201203.pdf

Here are the test results that the new requirement is based on:

http://www.clemson.edu/t3s/scdot/pdf/projects/SCDOT -Precast Caps- 7-11-2011.pdf

Also, take a look at this article in the March 2012 issue of Structure Magazine, it may not apply directly to your project, but has interesting conclusions:

http://www.structuremag.org/Archives/2012-3/C-StrucDesign-Feygin-Mar12.pdf

It recommends using omega-shaped stirups to surround the portion of the pile embedded in the cap. This is to make the pile-to-pile cap joint more ductile under high seismic loading.

http://www.SlideRuleEra.net

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[haynewp]

Thanks, coincidentally it is in SC.

 

[wannabeSE]

Thank you SlideRuleEra! I was not aware of the pile to cap connection problems. I just skimmed the magazine article and will read it soon.