# Estimating the sum of the vertical nodal force and area of a footing

**URL:** https://forum.itascainternational.com/t/estimating-the-sum-of-the-vertical-nodal-force-and-area-of-a-footing/1654
**Category:** FLAC3D
**Created:** [August 24, 2024, 6:49pm UTC](https://forum.itascainternational.com/t/estimating-the-sum-of-the-vertical-nodal-force-and-area-of-a-footing/1654 "2024-08-24T18:49:27Z")
**Posts on this page:** 5
**Page:** 1

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### Author: ![Adams](https://avatars.discourse-cdn.com/v4/letter/a/96bed5/32.png) [@Adams](https://forum.itascainternational.com/u/Adams)
#### Post date: [August 24, 2024, 6:49pm UTC](https://forum.itascainternational.com/t/estimating-the-sum-of-the-vertical-nodal-force-and-area-of-a-footing/1654/1 "2024-08-24T18:49:27Z")

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I am trying to estimate the sum of nodal forces and the area of a footing of radius 1, from the axis-symmetry line. I have tried different options such as putting all the gridpoints on that 1m into a list and summing all the forces on the gridpoints in the list. But when I fish list the contents of my loads it is not returning any value. It shows zero on the fish global symbol.

Please help if you have done this before.

Also, any book or manual to read to easily understand how fish works? I am new and just started learning FLAC

 ![FLAC Code](https://canada1.discourse-cdn.com/flex031/uploads/itasca/original/2X/e/edcb9b8f3beaf8b2282c00fb5423c92ac9e74249.png)

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### Author: ![dblanksma](https://avatars.discourse-cdn.com/v4/letter/d/858c86/32.png) [@dblanksma](https://forum.itascainternational.com/u/dblanksma)
#### Post date: [August 26, 2024, 3:00pm UTC](https://forum.itascainternational.com/t/estimating-the-sum-of-the-vertical-nodal-force-and-area-of-a-footing/1654/2 "2024-08-26T15:00:38Z")

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You need to call your function to return gridpoint forces _after_ cycling. You’re calling the function before an cycling has occurred.  
[FISH Scripting](https://docs.itascacg.com/itasca910/common/docproject/source/manual/scripting/fish_scripting/fish.html?node7619)

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### Author: ![Adams](https://avatars.discourse-cdn.com/v4/letter/a/96bed5/32.png) [@Adams](https://forum.itascainternational.com/u/Adams)
#### Post date: [August 26, 2024, 3:14pm UTC](https://forum.itascainternational.com/t/estimating-the-sum-of-the-vertical-nodal-force-and-area-of-a-footing/1654/3 "2024-08-26T15:14:30Z")

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Thank you for your response. I tried it after cycling, and I still had the same experience.

 ![FLAC BC](https://canada1.discourse-cdn.com/flex031/uploads/itasca/original/2X/3/3c0009bce30a5affe4eb27f206b5a907d6630792.png)

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### Author: ![dblanksma](https://avatars.discourse-cdn.com/v4/letter/d/858c86/32.png) [@dblanksma](https://forum.itascainternational.com/u/dblanksma)
#### Post date: [August 26, 2024, 3:21pm UTC](https://forum.itascainternational.com/t/estimating-the-sum-of-the-vertical-nodal-force-and-area-of-a-footing/1654/4 "2024-08-26T15:21:35Z")

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Hello @Adams,  
You are using the _gp.force.load()_ FISH function to return applied forces. However, you have only applied a velocity condition to the gridpoints. If you want to find the forces at specific gridpoints you will need to use _gp.force.unbal()_. See zone gridpoint FISH functions [here](https://docs.itascacg.com/itasca910/flac3d/zone/doc/manual/zone_manual/zone_fish/zone_fish.html?node3327#gp-functions).

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### Author: ![Adams](https://avatars.discourse-cdn.com/v4/letter/a/96bed5/32.png) [@Adams](https://forum.itascainternational.com/u/Adams)
#### Post date: [August 26, 2024, 3:29pm UTC](https://forum.itascainternational.com/t/estimating-the-sum-of-the-vertical-nodal-force-and-area-of-a-footing/1654/5 "2024-08-26T15:29:27Z")

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Thank you!! It returns the loads now.