Stresses magnitude at space frame nodes

Hi everybody,

1.I would like to know how to retrieve info on the magnitude of forces at the node points, as a result of 6 to 8 bars in compression or tension. Is there also a way to extract them at a .csv (or similar format) file? Similarly, is it possible to get all node displacements sorted out in such a file?

2.When it comes to gravity. does a vector (0,0,-1) represent g value of 9,81m/s^2 ? Is there a way to change the g magnitude as it fluctuates between 9,78 to 9,83?

3. Wind load case orientation, "Global"?

4.Snow load case orientation, "Global projection"?

5. Since I want to test an Ultimate Limit State load case (1,35*Gravity+1,5*Snow+1,5*Wind), how do I multiple the vectors with the safety factors?

Thank you in advance,

I would appreciate any kind of help, just to be sure that I dont get any garbage results

Attachments:

Testing.3dm, 80 KB
spaceframe_karamba_test.gh, 282 KB

Replies to This Discussion

Permalink Reply by Karamba3D on February 16, 2015 at 9:37am

Hi Jm,

ad 1.) you can get the cross section forces at the endpoints of beams and trusses using the 'Beam Forces'-component. It is part of the trial and student version. In case the a node not connect to a support then the individual force- and moment-components will sum up to zero.

You could stream the contents of a panel to a file and before that introduce ';' between the values.

ad 2.) (0,0,-1) represents a g value of 9.81m/s^2. For other values scale the vector supplied at the gravity-load component accordingly.

ad 3.) Wind acts mainly perpendicularly to a surface. Therefore a local orientation would be suitable.

ad 4.) For snow load 'global projection' is correct.

ad 5.) You can use the ModelView-component for that (see manual).

Best,

Clemens

Permalink Reply by jnm on February 24, 2015 at 3:04pm

Dear Clemens,

Thank you for your reply. Everything is clear except for ad 1. Given that I know the magnitude of forces at the end points of each bar, is it possible to substitute all forces - applied to each node - to one vector (direction and magnitude) for each node?

Best,

Permalink Reply by Karamba3D on February 25, 2015 at 1:02am

Dear jm,

you have to add the vectors at each node. In case of a node without a support and without an external point-load (I forgot that in the above comment) all components of the resultant vector should be zero.

Best,

Clemens

Permalink Reply by jnm on March 4, 2015 at 3:43am

Dear Clemens,

don't get me wrong, but as I am a beginner in GH and Karamba:

1.i would like to know how I can get all the forces' vectors as a list output. Or else, I don't find a way to select them in groups as applied to the nodes.

2.as for the case described above, for nodes without a support, without an external point load, but with snow+wind+equally distributed load, should the resultant vector still be zero?

Thanks again

Permalink Reply by Karamba3D on March 4, 2015 at 1:38pm

Dear jm,

if the sum of forces at a node would not add up to zero the node would not be in equilibrium. In what context do you want to use the magnitude of forces at the nodes?

You could disassemble the beams and sort them for their start and end nodes and co-sort the cross section forces.

Best,

Clemens

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