Dear all,
Plaxis HS small gives us the modulus reduction curves as shown below. However, it does not give the values in tabular form. Is there any spreadsheet available to obtain the values of the curves given by plaxis?
Hi Jamal,
Indeed the values are not given in a tabular form. However, they can be obtained using the equations mentioned in Chapter 7 of the Material Models Manual.
Dear Mr. Vasileios. Thank you. I am trying to write it in an excel, I will let you know if there is place where it does not connect. My main concern is, the modulus reduction curves recommended in the literature can be used to define the G/Gmax and damping values e.g. Vucetic Dobry for clays. In plaxis we can input, the gama0.7 value by reading from the curve where the G/Gmax= to 0.722. However due to the input of the other values (E50, Eur, m...) this curve sometimes is not close to the literature recommended values.
Though I have seen different estimations of gama0.7 in the literature.
(image attached below)
Effect of Jet-Grout Columns on the Seismic Response of Layered Soil Deposits, 2016, Pouya Sedighi.
Dear Vasileios Basas and Dennis Waterman any comment regarding the figure above. Thank you.
It is a stiffness degradation curve ..... You didn't ask anything about it, neither gave context why you put the graph. So I wouldn't know what comment to make and what you expect from us?
By the way, your remark that you can't always get the correct curve in PLAXIS compared to literature due to the input of other parameters like E50 and Eur puzzles me. Because the stiffness degradation curve in the HSSmall model is ONLY determined by G0 and gamma_0.7 and not by E50 and Eur. So whatever those last 2 parameters are, it won't make a difference for the small-strain stiffness curve.
With kind regards,
Dennis Waterman
Dear Mr. Dennis,
Thank you for your reply. Apologies for not explaining the question well.
1. In Hs small, I noticed that whenever the Eur ref value changes, the curves also change. Hence why I said it depends on the stiffness value E50 and Eoed ,since Eur also depends on these values.
2. Regarding the graph above, my question was, when selecting gama_0.7 value, the G/gmax at 0.722 value can be selected from the curves available in the literature (or an equivalent curve), is it possible as shown above to selct different G/gmax value and use them as input (instead of 0.722 value).
thank you.
Dear Jamal,
1) The tangent curve doesn't change with Eur, apart from the fact that Eur is the cut-off of the stiffness reduction curve, so with a different Eur the strength reduction curve is only cut off at a different point. But the equation of the strength reduction curve does not contain Eur. The secant curve is of course an average stiffness over a strain interval, so that indeed changes starting from the cut-off by Eur. But again, until the cut-off the secant curve is independent of Eur. So you have to be sure what curve literature gives you: a tangent curve or a secant curve....2) I have the feeling you're mixing two things. The parameter combination G0 + gamma_0.7 describe the shape of the curve. The graph above only indicate where in the small strain range one can find loose sand and dense sand: the indicated lines are not parameters that describe the curve. On the other hand, if you would have a different value like gamma_0.2 instead of gamma_0.7 it is not so difficult to fill in the HSsmall model a gamma_0.7 and calibrate it to match your gamma_0.2. Or you do it in a spreadsheet if you find that easier. Hence, there is no need for other input parameters as the would just describe another point on exactly the same stiffness degradation curve.
Thank you Mr. Dennis. Correct, indeed I have been mixing the two.
I saw your live meetings in person in Dubai and Netherlands I guess, where, for instance parameters of HS small and many other classes are to be held. Where I am at the moment, reaching these areas is almost impossible. Is there a webinar regarding HSsmall? Are the resources given at the end of those courses available for public? Or can we purchase them?
I don't think we're having a webinar on parameters of the HSsmall model. We do indeed teach about it in in-person courses. The material of those courses are handed out to the participants, but are not publically available as we consider that just the material without hearing the explanation has less value or could even be misunderstood which will lead to the incorrect use of the model.
I understand. Thank you Mr. Dennis.