Grasshopper

algorithmic modeling for Rhino

Dear Karamba users,

I have a problem with the location of supports in the cross-section of my structure. I have made a simple girder bridge structure consisting of two longitudinal steel girders, cross beams and a concrete deck slab on top.

From the results it seems that the supports are connected to the concrete slab, and the steel girders and cross beams are hanging below the slab. Because of this the cross beams are not utilized at all and the structure is not behaving as intended. I want the supports to be below the girders, and the concrete slab to be supported by the girders and the cross beams. 

Changing the eccentricities of the elements does not work since Karamba seems to align the whole structure back to the original centerpoints and connects the supports to the mesh resembling the concrete deck. Could anyone explain to me how to get the supports in the desired spot beneath the girders?

The GH file is attached, I am using the Karamba student version 1.1.0.

Edward

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Dear Edward,

all the reference nodes of the structural elements of your model lie in one plane. This causes a rigid shear connection between the beams and the bridge deck. In reality this will not be the case since the connection elements (e.g. shear studs) add some elasticity to the connection and the concrete creeps and shrinks.

It looks as though the cross beams are hardly utilized because their bending stiffness is small compared to that of the deck.

In case you want to decouple the deck from the substructure add small vertical pins between the beams and the deck and offset the deck a bit vertically upwards. Make sure however to model the shear connection correctly.

Best,

Clemens

P.S.: Why don't you use version Karamba 1.2.2?

Dear Clemens,

Thank you for your remarks, I will look into modelling the shear connection between the deck and the beams.

I am using this older student version since I bought the license more than a year ago, and according to your website all updates are only possible within one year. I have just been too lazy to buy a new license.

Edward

Dear Edward,

with your license you can install and run Karamba 1.2.2. and also later versions.
I may be that in future the availability of some new features will be dependent on the date of issue of the license.

Best,

Clemens

Hi, i have the same problem. How to create  a support when we have shell element. With beam element it seems easy but with my shell element i can't do it. I create a point as support but it doesn't work.

Sandra

Hi Sandra,

try to use the 'Mesh Breps'-component from Karamba/Utilities. There you can put points into the input-plug 'IPts' which shall be included in the resulting  mesh as vertices. Then create supports there.

Best,

Clemens

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