Grasshopper

algorithmic modeling for Rhino

Hi,

I am trying to create a truss column without bending moments in which the diagonals and the horizontals will be pinned in the two big vertical lines of the column. I used Karamba joint-agent in order to create hinges between the points but my model disappears. Can you please give me an advice on how I can connect my elements with joints?

Thanks

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Hi Olympios,

there were three bugs in your example (see attached definition).

Instead of creating rotational hinges at the diagonals you could define them as truss elements by setting 'Bending' to false via the ModifyElement-component (see manual).

Best,

Clemens

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Dear Clemens,

Thanks for your reply. This was an example that I tried to work on in order to fix the problem. In my real project I used the ModifyElement-component in order to avoid bending. The thing is that I don't know how to fix the problem with the rigid modes. I am trying to calculate a truss portal frame subjected to a wind load. I want all my connections to be pinned apart from the ones in the corners which have to be fixed. That is the reason that I tried to connect my elements with joint component. Can you please tell me how to fix this error?

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Dear Olympios,

in Karamba beams are only connected with each other if they have a common node. In the example above the girders of the truss need to be intersected with the diagonals (using e.g. the LineLine-intersection component) so that girders and diagonals have common nodes.

Best,

Clemens

Hi Clemens,

Thank you for your reply. I fixed my problem you are very helpful. I want to ask you one last thing. For the OptimizeCorssSection tool I tried to find out any reference on the technique that it follows but I am not sure. Is it using the fully utilized design (FUD) method in order to calculate the optimum cross section?


Best,

Olympios

Hi Olympios,

in each iteration the optimizer sets all cross sections such that they are below but as near to 100% utilization (according to EC3) as possible.

Best,

Clemens

Hi Clemens,

Thanks for your reply. I read somewhere that it uses ESO method in order to find the optimum cross section is this right? If yes which procedure is it because I found the book of Evolutionary Structural Optimization by Yi Min Xie (Author), Grant P. Steven. I appliedy the tool of OPCS to my model but when I go to utilization of model view I find bigger values than 100%. Also I tried to use AnalazythlII in order to calculate BModes but an errror was occured. Can you please help how to define those?

Best,

Olympios

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Hi Olympios,

please see the manual for details on the cross section optimization algorithm. It does not use the ESO method.

The utilization as output by the BeamView- or ShellView-component is the ratio between normal or Van Mieses stress and the material strength in every point of the cross section. This differs from the utilization calculated according to EC3. The latter applies to the cross section as a whole and includes e.g. the effect of buckling.

Best,

Clemens

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