2 emergent problem to solve in karambaa

problem in analysis old building and construction in reality

problem1 how to describe the line of beam, and the extension part of beam (in reality all of them are not connected in axis of the beam)

problem2 how to describe the beam fix in wall or pillar, (in karamba the wall might be define by one surface with karamba cross section component, so how to do with the beam? extent to wall ?

in karamba pillar is defined by axis line with cross section component,but the beam alway not on the axis of the pillar , so how to do with it in reality)

Attachments:

Replies to This Discussion

Permalink Reply by Karamba3D on January 19, 2016 at 11:23am

Dear Jiaxing,

it is possible to define eccentricities on beam cross sections. This can be done either per beam or per cross section (see manual).

By default elements which meet at a common point are rigidly connected. In order to solve problem 2 extend the line to the endpoint of the pillar.

For joining a beam with a wall use Karamba's 'Mesh Breps'-component. Plug the endpoint of your beam into the input-plug 'IPts' to make it a node of the mesh which can then be transformed into a patch of shell elements. Without further precautions this will however lead to a stress singularity at the connection point. In the finite element model the beam acts in relation toi the shel elements like an infinitely sharp needle. Thus the stiffness of the connection will tend to zero with increasing mesh refinement. For a proper connection one has to embed a short beam piece in the wall and connect the incoming beam to that.

Best,

Clemens

Permalink Reply by jiaxing on January 19, 2016 at 2:11pm

Dear clemens
thank u so much for this solution of eccentricity. it can solve my problem now.
and I have another question about the cross joint cr-start ct-end
how to identify the stiffness above, do we have some standard?
now I need to define some typology of hinge in karamba, didn't test those before, if you could provide some basic cases set up to hinge part of steel joint i would really appreciate that
best best best to vienna
from bejing Lu

Permalink Reply by jiaxing on January 19, 2016 at 2:10pm

Dear clemens

thank u so much for this solution of eccentricity. it can solve my problem now.

and I have another question about the cross joint cr-start ct-end

how to identify the stiffness above, do we have some standard?

now I need to define some typology of hinge in karamba, didn't test those before, if you could provide some basic cases set up to hinge part of steel joint i would really appreciate that

best best best to vienna

from bejing Lu

Permalink Reply by Karamba3D on January 20, 2016 at 12:21pm

Dear Lu,

if you are not sure about the stiffness of a joint, choose zero. For steel structures with standard cross sections (which do not buckle locally but develop yield hinges) this always lies on the safe side. For stiffness values of steel connections take a look at textbooks on structural steel design.

Examples with hinges can be found in the installation folder of Karamba under '...\Rhinoceros 5.0 (64-bit)\Plug-ins\Karamba\Examples\TestExamples\Beam_Joint'.

Best,

Clemens

Permalink Reply by jiaxing on January 24, 2016 at 7:07am

Dear Clemens

Thank u very much about those suggestion above.

about the book <Structural Steel Designer's Han - Roger Brockenbrough>

this is what I find , but did not find the stiffness of hinge in it

Permalink Reply by jiaxing on January 24, 2016 at 7:14am

maybe this way is more directly for me to understand the translate and rotate on detail joint model ,now I'm confused by this 4 joints

1

2

Permalink Reply by Karamba3D on January 26, 2016 at 2:14am

If the bolts are neither prestressed nor fitted screws all the bolted connections above should be modelled as hinges with zero rotational stiffness about the local Y-axis. The reason is that the diameter of screws holes is normally somewhat larger than the bolt (e.g. 1mm for a 12mm diameter bolt) so that the connected beam can rotate slightly. In case that the screws are prestressed the connections can be modelled as rigid.

Since steel is a plastic material it is always on the safe side to introduce hinges in a steel structure (see 'lower bound theorem of plasticity'). So in case you are not sure about the stiffness of a connection you can introduce a hinge without compromising structural safety.

Best,

Clemens

Permalink Reply by jiaxing on January 24, 2016 at 7:19am

maybe it is easy for me to understand those 4 joint on