# What is the problem to use PH Model with Small Strain Option in dynamic analysis? **URL:** \ **Category:** FLAC3D\ **Created:** [May 11, 2022, 11:18pm UTC](https://forum.itascainternational.com/t/what-is-the-problem-to-use-ph-model-with-small-strain-option-in-dynamic-analysis/516 "2022-05-11T23:18:45Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![MiguelN](https://avatars.discourse-cdn.com/v4/letter/m/6f9a4e/32.png) [@MiguelN](https://forum.itascainternational.com/u/MiguelN)\ **Post date:** [May 11, 2022, 11:18pm UTC](https://forum.itascainternational.com/t/what-is-the-problem-to-use-ph-model-with-small-strain-option-in-dynamic-analysis/516/1 "2022-05-11T23:18:45Z")
Hi everyone. I have read that hardening soil model with small strain option can be used for dynamic analysis. So, what is the problem in FLAC with PH with small strain option? Please, could you explain with more details this paragraph of the manual: “The Plastic-Hardening model with small-strain stiffness is not recommended for fully dynamic problems with random unloading-reloading paths that lead to nested hysteretic loops” Thanks in advance. ---
**Author:** ![MiguelN](https://avatars.discourse-cdn.com/v4/letter/m/6f9a4e/32.png) [@MiguelN](https://forum.itascainternational.com/u/MiguelN)\ **Post date:** [May 11, 2022, 11:35pm UTC](https://forum.itascainternational.com/t/what-is-the-problem-to-use-ph-model-with-small-strain-option-in-dynamic-analysis/516/2 "2022-05-11T23:35:26Z")
Please to confirm that this paper respond the question. thanks in advance. [Cudny-Truty2020\_Article\_RefinementOfTheHardeningSoilMo.pdf](https://forum.itascainternational.com/uploads/short-url/hjUYtKQmvDOixfBxEeZI2HFBWeV.pdf) (3.3 MB) ---
**Author:** ![cheng](https://avatars.discourse-cdn.com/v4/letter/c/ecccb3/32.png) [@cheng](https://forum.itascainternational.com/u/cheng)\ **Post date:** [May 12, 2022, 2:33pm UTC](https://forum.itascainternational.com/t/what-is-the-problem-to-use-ph-model-with-small-strain-option-in-dynamic-analysis/516/3 "2022-05-12T14:33:41Z")
Yes, this paper explained that. Please note that PH model has implemented this “brick” algorithm and solved the problem, but only from the next version. ---
**Author:** ![MiguelN](https://avatars.discourse-cdn.com/v4/letter/m/6f9a4e/32.png) [@MiguelN](https://forum.itascainternational.com/u/MiguelN)\ **Post date:** [May 12, 2022, 4:08pm UTC](https://forum.itascainternational.com/t/what-is-the-problem-to-use-ph-model-with-small-strain-option-in-dynamic-analysis/516/4 "2022-05-12T16:08:12Z")
Thank you Cheng for your answer and really are good news about the implementation of this Brick algorithm for PH model (or HS model) for the next version of FLAC3D. ---
**Author:** ![musicinquark](https://yyz1.discourse-cdn.com/flex031/user_avatar/forum.itascainternational.com/musicinquark/32/938_2.png) [@musicinquark](https://forum.itascainternational.com/u/musicinquark)\ **Post date:** [November 27, 2023, 8:26pm UTC](https://forum.itascainternational.com/t/what-is-the-problem-to-use-ph-model-with-small-strain-option-in-dynamic-analysis/516/5 "2023-11-27T20:26:51Z")
Hello Cheng, Is the statement in the user manual still valid, or has it become usable after the implementation of the Plastic Hardening model with SS Brick model in the new version? Thank you. [Plastic-Hardening (PH) Model\* — FLAC3D 7.0 documentation](https://docs.itascacg.com/flac3d700/common/models/hardening/doc/modelhardening.html#equation-modelpheqgs:~:text=The%20detailed%20algorithm,nested%20hysteretic%20loops). ---
**Author:** ![cheng](https://avatars.discourse-cdn.com/v4/letter/c/ecccb3/32.png) [@cheng](https://forum.itascainternational.com/u/cheng)\ **Post date:** [November 27, 2023, 8:52pm UTC](https://forum.itascainternational.com/t/what-is-the-problem-to-use-ph-model-with-small-strain-option-in-dynamic-analysis/516/6 "2023-11-27T20:52:52Z")
The new Brick algorithm was implemented in v9. Unfortunately, it was not back into v7. See the new doc in v9: [Plastic-Hardening (PH) Model\* — FLAC3D 9.0 documentation](https://docs.itascacg.com/itasca900/common/models/hardening/doc/modelhardening.html?node1220) A comparison is here: ![image](https://canada1.discourse-cdn.com/flex031/uploads/itasca/original/1X/b4419fcbef39c24ab566c8cba44acd00988791eb.jpeg) ---
**Author:** ![musicinquark](https://yyz1.discourse-cdn.com/flex031/user_avatar/forum.itascainternational.com/musicinquark/32/938_2.png) [@musicinquark](https://forum.itascainternational.com/u/musicinquark)\ **Post date:** [November 27, 2023, 9:13pm UTC](https://forum.itascainternational.com/t/what-is-the-problem-to-use-ph-model-with-small-strain-option-in-dynamic-analysis/516/7 "2023-11-27T21:13:32Z")
I knew that but when I see that statement I was confused. I thought I was navigating within the documentation of v9.0. Sorry 🙂 Thanks for the answer.