I have to analyze the behaviour of piles under tension loads (settlements...). For the skin friction I have to consider, may I use the same parameters as for the compression loads, or does the fenomenon change so that I have to use coefficients or a completely different model? Thank you in advance,
There is a theoretical treatment on adjustment for radial contraction of tension piles on page 100 of the book
Piling Engineering Fleming WGK Weltman AJ Randolph MF and Elson WK 2nd Edition 1992 Spon
It is noted that for typical piles the reduction in skin friction may amount to 10% to 20%.
It is however stated in the book over this analysis that current opinion is that there is no systematic difference in the mobilized skin friction for compression and tension piles except for relatively slender piles. Refer to the book for more detail.
Given the uncertainties in estimating soil parameters and earth pressure coefficients I don't think that a 10% or 20% difference would be worth taking into consideration.