# the parameters of Strain in blades and tower

**URL:** <https://forums.nlr.gov/t/the-parameters-of-strain-in-blades-and-tower/2353>\
**Category:** Rotor Aerodynamics\
**Created:** [November 7, 2020, 11:12pm UTC](https://forums.nlr.gov/t/the-parameters-of-strain-in-blades-and-tower/2353 "2020-11-07T23:12:36Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![Jason.Jonkman](https://dub1.discourse-cdn.com/nrel/user_avatar/forums.nlr.gov/jason.jonkman/32/3086_2.png) [@Jason.Jonkman](https://forums.nlr.gov/u/Jason.Jonkman)\
**Post date:** [November 9, 2020, 4:10pm UTC](https://forums.nlr.gov/t/the-parameters-of-strain-in-blades-and-tower/2353/2 "2020-11-09T16:10:17Z")

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Dear Gaoshuai,

The ElastoDyn module of FAST / OpenFAST does not output strain directly; rather, ElastoDyn can output deflection at a node. The term “strain gage” is used simply to mark a node in ElastoDyn where response outputs (deflection, sectional loads) can be output.

The definitions of TwrGagNd, etc. have been discussed several times on this forum, e.g., see: [fore-aft and side-to-side accelerations at mid-tower - #4 by Jason.Jonkman](http://forums.nlr.gov/t/fore-aft-and-side-to-side-accelerations-at-mid-tower/1911/4).

Best regards,

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