# 3DEC 9: Plain concrete model in structural analysis - damage factors and characteristic length

**URL:** <https://forum.itascainternational.com/t/3dec-9-plain-concrete-model-in-structural-analysis-damage-factors-and-characteristic-length/1434>\
**Category:** 3DEC\
**Created:** [May 2, 2024, 10:53am UTC](https://forum.itascainternational.com/t/3dec-9-plain-concrete-model-in-structural-analysis-damage-factors-and-characteristic-length/1434 "2024-05-02T10:53:59Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Damir](https://avatars.discourse-cdn.com/v4/letter/d/7993a0/32.png) [@Damir](https://forum.itascainternational.com/u/Damir)\
**Post date:** [May 2, 2024, 10:53am UTC](https://forum.itascainternational.com/t/3dec-9-plain-concrete-model-in-structural-analysis-damage-factors-and-characteristic-length/1434/1 "2024-05-02T10:53:59Z")

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Hi everbody!

Is it possible to access damage factor D (or Dc, Dt) via Fish command, such as “block.zone.state ()” or something similar. And, does anybody have suggestion about characteristic lengths (lc or ld) if “block zone generate-new” and “block zone nodal-mixed-discretization” are used. Of course, some FEM rules exist, but are they valid for the NMD strategy?

Thanks!

Damir

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**Author:** ![jhazzard](https://avatars.discourse-cdn.com/v4/letter/j/4af34b/32.png) [@jhazzard](https://forum.itascainternational.com/u/jhazzard)\
**Post date:** [May 2, 2024, 10:00pm UTC](https://forum.itascainternational.com/t/3dec-9-plain-concrete-model-in-structural-analysis-damage-factors-and-characteristic-length/1434/2 "2024-05-02T22:00:19Z")

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You can use block.zone.prop(zp,‘damage-compression’) or block.zone.prop(zp,‘damage-compression’) etc. See the property names [here](https://docs.itascacg.com/itasca900/common/models/concrete/doc/modelconcrete.html?node1226).

Maybe @cheng can comment on the other part of the question?

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**Author:** ![cheng](https://avatars.discourse-cdn.com/v4/letter/c/ecccb3/32.png) [@cheng](https://forum.itascainternational.com/u/cheng)\
**Post date:** [May 14, 2025, 9:43pm UTC](https://forum.itascainternational.com/t/3dec-9-plain-concrete-model-in-structural-analysis-damage-factors-and-characteristic-length/1434/3 "2025-05-14T21:43:15Z")

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> [@Damir](#):
>
> characteristic lengths

Using ‘characteristic lengths’ to reduce grid dependency is only an approximation and cannot completely eliminate grid dependency, as it is influenced by factors such as zone size distribution, load direction, and others. Although not explicitly tested, it is still expected to help reduce grid dependency even when using the NMD strategy.