Interface stiffness factor: Embedded beam row

Dear Mr. Dennis, 

Yeah, I checked with the relative displacement and the result is correct. Really great help. 

Thanks. 

Dear Nitharshan,

1) It's almost correct ..... you're using the absolute displacement of the pile, but that should of course be the relative displacement, that is relative to the soil. Because it's the difference between pile and soil displacement that causes the friction.

2) For embedded beams the R_inter parameter is not used, because the ISF's already take care of the interface reduction. That is why the equation says "G_soil" and not "G_i".

Hence, the difference you find is probably because you use the absolute displacement instead of the relative displacement.

With kind regards,

Dennis Waterman

If anyone knows the answer, please reply which will help me a lot. 

Thanks. 

Thanks for the reply. 

Can you please advice of the following (questions are provided in the attached screenshot)? 

Thanks.

Dear Nitarshan,

Q1).  The equations to do so are actually given in the validation article below figure 2.

Q2).  Think physics ... how can one limit the capacity of a spring? Well, by connecting one end to some kind of sliding construction with a certain maximum friction. When the spring force exceeds the maximum friction of the slider, the slider will start sliding and thus the spring force cannot increase anymore. Hence, the "slider" is what limits the skin friction to tau_max.

Q3). First of all, the installation effects of bored piles are rather small (compared to driven piles) and testing has shown that the installation effects also don't last very long. Hence, within months after installing bored piles the bearing capacity of bored piles are what one could expect as if no installation effects would have taken place.
So assuming installation effects are minor, the default situation is based on the most suitable allround model for soil, which is HSsmall, and based also on what is a common situation in which pile foundations are used. Those are often soft clay or peat areas with high groundwater level. Therefore a  groundwater level at soil surface was chosen.

Q4) Unfortunately the plots are not on the same scale. The right plot has a skin friction at the foot that is more than 2x higher than the left plot, but clearly it's not plotted as 2 times higher. So I think on the same scale the plots would actually not be that different, apart from the fact that in the right one the skin friction increases with depth for the lower 25% of the pile.
Just based on the plot there is not much to conclude. The skin friction depends on the relative displacement between pile and soil and is limited by the skin resistance. The skin resistance is different in both cases because of the different ISF values. So maybe the skin friction was redistributed in both cases - you could check that by checking mobilised skin resistance. But as said, just from two plot it's impossible to say why the distributions are different.

With kind regards,

Dennis Waterman