prestressed augercast soldier pile

huangyhg

:prestressed augercast soldier pile
anyone have any success or experience in using a special design of sequentially prestressed augercast soldier pile instead of the normal wide flange sections or tiebacks, including soil nailing?
have a project where no tiebacks can be used and i am trying to minimize, or eliminate entirely, the use of interior rakers in the pit - three to four story cut.
i anticipate gradually prestressing the piles with multiple tendons, strategically placed in the 30" diameter pile, as the excavation progresses to avoid tension in the concrete, enabling the use of the gross i section for lateral deflection.  
any thoughts?   
mike mccann
mmc engineering
i guess this is something either new or not used much if at all.  thanks.
mike mccann
mmc engineering
i would contact vsl. if something has been done with prestressing, its likely they have done it.
if you are in the us, we have found vsl's houston office to be quite helpfull on a lot of issues involving prestressing/post-tensioning.  
although i don't get involved personally, prestressing cocnrete piles is standard practice for geotech engs here in new zealand...  very commonly done, and quite successful.  as i understand it there are dangers involved if the pile is not braced by soil around it, so i am not certain the application is a fit...
also, just for your information, i believe the piles typically have a single, central, debonded prestressing cable and rather than a group.  if you like i can have a word with a buddy in geotechnical group and see what he says.
cheers,
ys
b.eng (carleton)
working in new zealand, thinking of my snow covered home...
youngstructural:
yes, could you please - our geotech has not heard of such an application, yet.  and he is very experienced - could be the economics here.  nevertheless, i want to know oneway or the other.  thanks.
mike mccann
mmc engineering
hello mike;
sorry, i should have warned you, but this is a long week-end in nz.  i've just checked my posts and seen your's now...  i'll talk to one of the boys tomorrow and let you know.
cheers,
ys
b.eng (carleton)
working in new zealand, thinking of my snow covered home...
i ran some quick numbers and it seems like i would have to use 30" diameter pile to be feasible to do this for the loads i am seeing, considering f'c = 5000 psi concrete and an uncracked section.  seems like it should work for a cantilever of 20 feet or so, depending on the lateral soil loads, but not much greater if at all.  still, i would be able to eliminate the top set of rakers.  question is, is it economical considering the extra labor and another discipline...   
mike mccann
mmc engineering