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Re: Drilled Pier/pile-Support is pinned or fixed

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In my oppinion a 100% pinned connection(if finally assumed in the design)should be very carefully detailed and materialised at the site.
In addition to the above, I again believe,that the performance of a pinned connection can not be practically guaranteed especially at locations
very difficult to inspect(and even more difficult to repair, should that be necessary).
I am sure that as your piles will pass thru a 3 to 5 mthick comressible layer your design addresses also the issues of
- negative skin friction(can cause signifficant increase of the axial load) and
- the small lateral support in the top 3 to 5 m(could be critical particularly in seismic regions where high horizontal forces are transmitted).
Of course, I don't know the particulars of your project however introducing pile caps,monolithic pile-to-pile cap connection and more than
one pile per column would be a worth considering alternative if the project was in my end (Greece).
john n. sigalas
----- Original Message -----
Sent: Wednesday, August 30, 2006 8:43 AM
Subject: Drilled Pier/pile-Support is pinned or fixed

Hello All,

I am designing a pile/drilled pier foundation for a building. I want to reduce the support forces so that I can reduce the no. of piles/pier. The columns are almost 20m high. I would like to know whether I can take base as pinned in analysis if I am using singe piles/piers for each column. The pile/drilled piers are around 6 to 10 m deep. The piles/piers here are designed based on skin friction with a pile socket length in rock of 3 to 6m. The rock is of poor quality with RQD (Rock Quality Designation) 0% to 50%. These are from Geotechnical report. I would like to mention that the soil up to 3 to 5m from Pile/Pier head is mainly of hydraulic fill material. N value of top soil varies from 35 to 4. The site is in a reclamation area.

Thanks in advance,



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