Beam on elastic foundation

[mick]

Hello, 

  I'm building a model in which some of the boundary conditions can be applied as distributed spring along beams (i.e. the so-called winkler foundation) .

Normally if we consider a spring on a node (discrete element), the stiffness is defined in units FORCE / DISPLACEMENT. 

In the case of winkler foundation, the stiffness is defined in units FORCE / (DISPLACEMENT * BEAM_LENGTH). I could certainly calculate manually the length of each beam, and assign the equivalent spring stiffness at the nodes. But for many beams of variable length, the procedure is time-consuming.

Is there any command in lsdyna to assign a distributed foundation stiffness?

Thanks in advance,

Mick

[l...@schwer.net]

Rather than use spring elements, consider using 2D Plane Stress shells ELFORM=12 on *SECTION_SHELL edge on under each beam.

 

The shell thickness (t) would be the same as the beam thickness and the equivalent spring stiffness would be  K=Area*E/d where E is the soil elastic modulus, Area=beam length (w) * thickness (t) and d is the depth of the soil.

                                --len

 

 

From: ls-d...@googlegroups.com <ls-d...@googlegroups.com> On Behalf Of mick
Sent: Thursday, September 1, 2022 9:14 AM
To: LS-DYNA2 <ls-d...@googlegroups.com>
Subject: [LS-DYNA2] Beam on elastic foundation

 

Hello, 

  I'm building a model in which some of the boundary conditions can be applied as distributed spring along beams (i.e. the so-called winkler foundation) .

 

 

Normally if we consider a spring on a node (discrete element), the stiffness is defined in units FORCE / DISPLACEMENT. 

In the case of winkler foundation, the stiffness is defined in units FORCE / (DISPLACEMENT * BEAM_LENGTH). I could certainly calculate manually the length of each beam, and assign the equivalent spring stiffness at the nodes. But for many beams of variable length, the procedure is time-consuming.

 

Is there any command in lsdyna to assign a distributed foundation stiffness?

 

Thanks in advance,

Mick

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[mick]

Thank you Len,

   in lack of a specific option, your suggestion is a clever workaround.

Best,

Mick