Add bodyforce

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Lei Lei
Posts: 98
Joined: Mon Jul 10, 2023 1:28 pm

Add bodyforce

Post by Lei Lei » Sat Jun 01, 2024 1:44 pm

Dear STKO Team,

I noticed various body force settings in multiple places within STKO, such as the density of some materials (e.g., PressureDependentMultiYield), the body force in the elements (e.g., quad), and the mass or load in Conditions.

Could you please explain the differences between these settings? Do they impact calculations?

Looking forward to your reply!

kesavapraba
Posts: 348
Joined: Sat Mar 28, 2020 2:25 pm

Re: Add bodyforce

Post by kesavapraba » Mon Jun 03, 2024 7:21 am

Density and mass are associated with dynamics analysis, they will not add any static structural loads, as the other (body force and load) do. If you specify density of the material, the equivalent mass at nodes for the elements are internally calculated and assigned. Otherwise, you should manually calculate the mass and assign at the nodes. So, density option for material adds a layer of sophistication.
:: With best wishes ::
Prabakaran Kesavan

Lei Lei
Posts: 98
Joined: Mon Jul 10, 2023 1:28 pm

Re: Add bodyforce

Post by Lei Lei » Mon Jun 03, 2024 9:01 am

kesavapraba wrote:
Mon Jun 03, 2024 7:21 am
If you specify density of the material, the equivalent mass at nodes for the elements are internally calculated and assigned. Otherwise, you should manually calculate the mass and assign at the nodes. So, density option for material adds a layer of sophistication.
It seems that the body force within the element also contributes to this sophistication.

STKO Team
Posts: 2309
Joined: Tue Oct 29, 2019 8:45 am

Re: Add bodyforce

Post by STKO Team » Tue Jun 04, 2024 7:32 am

Yes some elements have the body force as input.
But not all of them, that's why in STKO we developed utilities such as VoulumeForce, FaceForce, EdgeForce... to provide for distributed forces where not available in OpenSees

Lei Lei
Posts: 98
Joined: Mon Jul 10, 2023 1:28 pm

Re: Add bodyforce

Post by Lei Lei » Tue Jun 04, 2024 7:47 am

So, for face force, should I consider the thickness of the quad element?

STKO Team
Posts: 2309
Joined: Tue Oct 29, 2019 8:45 am

Re: Add bodyforce

Post by STKO Team » Thu Jun 06, 2024 8:10 am

A FaceForce is a pressure F/L^2, so yes, you can compute it as self-weight (F/L^3) times the thickness

Lei Lei
Posts: 98
Joined: Mon Jul 10, 2023 1:28 pm

Re: Add bodyforce

Post by Lei Lei » Thu Jun 06, 2024 12:17 pm

Alright, I think Opensees will time the thickness automatically.

Thanks for your reply!

kesavapraba
Posts: 348
Joined: Sat Mar 28, 2020 2:25 pm

Re: Add bodyforce

Post by kesavapraba » Fri Jun 07, 2024 4:42 am

You need to multiply the self-weight (either in N/m3 or kN/m3) with the corresponding thickness and apply it as face force (STKO automation) along the inplane direction of the quad element.
:: With best wishes ::
Prabakaran Kesavan

Lei Lei
Posts: 98
Joined: Mon Jul 10, 2023 1:28 pm

Re: Add bodyforce

Post by Lei Lei » Fri Jun 07, 2024 4:51 am

Thanks for your reply!

Best wishes!

STKO Team
Posts: 2309
Joined: Tue Oct 29, 2019 8:45 am

Re: Add bodyforce

Post by STKO Team » Mon Jun 10, 2024 8:17 am

You're welcome

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