Different utilization of the same cross section

Hello Karamba

When I am modelling a simple beam i found that the utilization component gives different values for the calculated utilization. The difference occur then I choose the cross section from either the CrossSecSelect component or the Cross Sections component. As You can see from the images, the difference occur no matter what cross section I choose.

The set up for both beams are the same, so is the load.

The values used in the Cross Sections component i taken from the Euronorm 19:1957.

Best regards,

Silas

Attachments:

IPE220.PNG, 112 KB
HEB300.PNG, 112 KB
HEM600.PNG, 113 KB

Replies to This Discussion

Permalink Reply by Karamba3D on December 5, 2018 at 2:32am

Hello Silas,

thanks for your post! I will check that.

Best,

Clemens

Permalink Reply by Silas Wettendorff Pedersen on December 5, 2018 at 5:07am

Hey Clemens,

I have also found out that Karamba can not reduce the buckling length when e.g. when you have a column that is fixed at the buttom and simply supported at the top.

Is there a way to incorporate the correct length, or is it a limitation?

Best regards,

Silas

Permalink Reply by Karamba3D on December 5, 2018 at 1:02pm

Hi Silas,

in case the true buckling length deviates from the simplified assumptions used by Karamba3D (see the manual for details), one can set the buckling length via the 'Modify Element'-component.

Best,

Clemens

Permalink Reply by Silas Wettendorff Pedersen on December 6, 2018 at 5:17am

Hey Clemens,

Thanks for the reply, I wasnt aware of that you can manually set the buckling length.

Best,

Silas

Permalink Reply by Karamba3D on January 6, 2019 at 9:34am

Hello Silas,

the reason for the difference in utilization in Karamba3D 1.3.1. is a deviation of the St. Venant torsional constant 'It' between the values of the cross section tables and those calculated for custom I-profiles.

The 'It' value in the crossection tables of Karamba3D includes the junction enhancement at the connections between flanges and web (see e.g. https://www.steelconstruction.info/File:Sci_p385.pdf?internal_link). This effect gets more significant with increasing fillet radii. The calculated values for custom I-profiles currently do not take this into account and are therefore on the conservative side.

In the next release of Karamba3D the junction enhancement will be added for fillet radii larger than zero. In case of zero fillet radius a welded section will be assumed.

Best,

Clemens

RSS