Shear modulus "G"

Dear all,

i am using the "Matselect" - component to define a new Material. I try to define a material "Steel cable" which should be limp (biegeschlaff). Shear = 0. My understanding: shear modulus G = 0.

The manual says:

"The shear modulus G describes material behavior in this respect. It is includedin the MaterialProps component for completeness. Currently Karambadoes not take account of this property."

I modify the MaterialProperties.csv. Please see image. G = 0 doesnt work, so I put G = 1.

Do the shear modulus G work today?

thanks

Jörg

Attachments:

Mat Steel cable.png, 83 KB

Replies to This Discussion

Permalink Reply by Karamba3D on November 10, 2011 at 8:03am

Dear Jörg,

thank you for your hint that G=0 causes problems.This will be corrected in the next release.

Karamba does not take shear deformation into account. In case of small ratios of cross section height to span - which is normally the case - the influence of shear deformation can be neglected.

For creating a beam with small bending stiffness chose a cross section with small height (i.e. small bending stiffness). When gravity is present this element will show excessive deflections. The reason is that Karama currently does only geometrically linear deflection calculations: the influence of the deformed state on the stiffness of a system is not take into account. For ropes however this influence is decisive. So if you want to include ropes in your model there are two work-arounds:

1.) Assume that the rope is pre-stressed: in this case you can replace the rope with a truss element which has no bending stiffness.

2.) Add the external loads in small steps and take the deflected model of one step as the input of the next. This will give a rough approximation of the resulting deflections. Another possibility for arriving at the deflected state is to use Kangaroo which can handle geometric nonlinearity due to its explicit solution scheme. Take the final deflected model and apply the full load in order to get values for strain, stress and utilization.

Best regards,

Clemens

Permalink Reply by Joerg Guettgemanns on November 14, 2011 at 1:06pm

Dear Clemens,

maybe I send reply a second time, my fault.

Thanks for answering. I use prestressed beams as wires. I use the beam modifier to define trusses. (read chapter 5.9.1)

How can i modify the "wires-beams" that they only show color of tension (blue)?

Please see attached svreenshot.

Best regards

Jörg

Attachments:

bridge01.jpg, 1.3 MB

Permalink Reply by Karamba3D on November 14, 2011 at 2:15pm

If you want to get rid of the yellow and purple colors set the 'Render Colormargin' in subsection 'Render Settings' of the ModelView-component to 100%.

Best regards,

Clemens

Permalink Reply by Joerg Guettgemanns on November 18, 2011 at 12:52pm

Dear Clemens,

thank you for helping me. I finished my first karamba project and posted it on my blog www.attitudegeometries.wordpress.com

I hope there will be a lot of projects in the future. Karamba is great tool. Thanks for sharing.

Best regards

Jörg

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