Extreme, "rogue", load values when applying wind load to tower as a mesh load?

Hi again,

On a simillar topic to my recent post, I'm struggling to model a wind load.

The façade points/nodes on which the wind acts are determined following the same method as the "Twisted Tower" tutorial on the Karamba 3d website.

3 different wind pressures (---> 3 different mesh loads) are applied, increasing with altitude as per Eurocode calculations:

0-32m : 550,59 N/m2

32-64m : 729,80 N/m2

64-100m : 867,85 N/m2

Care has been taken to ensure no superpostion of forces at 32m & 64m.

550,59 N/m2 is transmitted to floor slabs @ 0m, 4m, 8m, 12m, 16m, 20m, 24m & 28m.

729,80 N/m2 is transmitted to floor slabs @ 32m, 36m, 40m, 44m, 48m, 52m, 56m & 60m.

867,85 N/m2 is transmitted to floor slabs @ 64m, 68m, 72m, 76m, 80m, 84m, 88m, 92m, 96m & 100m.

When the loads are visualised simultaneously in Karamba, one obtains, as anticipated, a "stepped" distribution with point loads increasing with altitude (Image_1).

Ex:

46 @ 0-34m

60 @ 34-64m

72 @ 64-100m

However, you will also notice several "rogue" point loads at the outer edges, presenting very large values (500-1000) (Image_1 & Image_2).

Would anyone know why these appear and/or have any ideas as to what can be done to correct things? I suspect an issue with the way the tower is meshed?

Many thanks in advance for any feedback you may provide,

Nathan

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Permalink Reply by Karamba3D on July 8, 2018 at 1:49pm

Hi Nathan,

I think the problem is that the mesh where you apply the MeshLoad covers the whole facade (~10000m²), whereas the nodes of the structure to which the loads shall be applied, only cover a third of one side of the building.

If you plug a mesh-load object into a panel you get its area and the resultant load.

Best,

Clemens

Permalink Reply by Nathan Stuckey on July 9, 2018 at 4:43am

Hi Clemens,

Thank you very much for your feedback. Are you therefore suggesting that I create distinct meshes for each of the three mesh loads? Would you have any tips regarding how to fine tune the meshes for optimal accuracy?

Thanks again, I really appreciate it!

Nathan

Permalink Reply by Karamba3D on July 10, 2018 at 12:34am

Hi Nathan,

either use three distinct meshes or a variable MeshLoad. The latter is available in Karamba3d 1.3.0 upwards and lets you define the surface load for each mesh face separately.

The mesh for the MeshLoad should be finer than the underlying structural geometry. The 'Length/Segment' property of ModelView/RenderSettings impacts the distribution of MeshLoads on beams and trusses (see the manual for details).

Best,

Clemens

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