Error Rigid body's

Hi,

I'am getting the following error message when i want to analyze my structure:

1. There are 2 rigid body modes in the system. This means some parts can move freely without causing deformation.
Try to use the 'Eigen Modes'-component and activate the display of local coordinate axes: The first eigen-mode will be the rigid body motion.
If this does not help, check whether you have a pinned support directly attached to a hinge. A hinge introduces an extra node which may cause the problem.
When analyzing a flat shell structure one has to lock the rotation perpendicular to the plate in at least one node.

I don't know what the error message means. Is there a way to know where the rigid body modes are or the parts that can move freely?

I used that Eigen Modes component, but it shows me really weird kind of structure when i activate it.

I attached the file to the Discussion what i have mad so far.

Attachments:

Steel hall.gh, 42 KB

Replies to This Discussion

Permalink Reply by Karamba3D on February 28, 2017 at 12:54pm

Hi Giorgio,

there were duplicate points in the system which caused some parts of the structure to be disconnected from the rest.

It is not necessary to input the endpoints of the elements into the Assemble-component (see attached definition). This option is meant for cases when one explicitly wants to generate multiple points at the same position.

You can detect the rigid body movements by specifying a small scaling factor for the displacements in the ModelView-component (Display Scales/Deformation - double-click on the nob to adjust the number range). Another possibility is to use the 'Eigen Modes'-component.

In order to detect duplicate nodes enable 'Node tags' in ModelView/Structure Tags.

Best,

Clemens

Attachments:

Steelhall_cp.gh, 38 KB

Permalink Reply by Giorgio on March 1, 2017 at 3:50am

Thanks man! I will compare it with my old file and see what you meant and what i did wrong. Once again thank you very much.

Now just one more question, i want to change the steel type to S460, but the MatSelect component only got till S355 if im right. Is there a possibility to change the steel type to S460?

Permalink Reply by Karamba3D on March 1, 2017 at 12:33pm

You can define a custom material or add S460 in the material data base. This is a CSV file which can be opened and edited with a text editor or any spread sheet software (see manual).

Permalink Reply by Giorgio on March 7, 2017 at 2:27am

Thanks for the info! Going to change it. Now i got an other problem with my structure. It gives the following error:

1. 12 cross sections need to be bigger than their biggest family member.

I tried to make the lines between the strusses to be one with the whole structure, but when i connect the line to beam component to the Assemble model, it doesnt work and gives me this error. Is it that the lines arent conected on the other points?

Attachments:

Steelhall_Not_Working.gh, 40 KB

Permalink Reply by Matthew Tam on March 9, 2017 at 1:02am

Hi Giorgio,

When the Optimize Cross Section component returns this message, it means that the largest cross section is not large enough to satisfy the conditions that you set, ie they do not meat the Max Util/Max Displ that is set in the component. Either you should edit the settings for the two inputs or you should increase the domain for the cross section sizes.

However I believe that your problem arises due to the long beams (Dwars) not being split at the intersections with the trusses and therefore are giving you inaccurate results.

best ,
Matthew

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