I am currently trying to apply loads to a cable net that will eventually have plants growing on it. Because these plants may grow thick enough to eventually gather snow and wind loads, I wanted to apply an area load across the net using LAR. I have done this before for beam systems, but I get an error (“no supporting elements [beams] found”) when I try to do this for the cable elements. This makes sense since I only have cable elements, but I was wondering if anyone knows another way to do this for cable elements. The cable net is extremely irregular, so applying a line load would not allow for a good approximation, but it is my back up plan if no other options are possible.
Best,
Grant
DeepL Translation:
Hallo zusammen,
ich versuche gerade, Lasten auf ein Kabelnetz aufzubringen, auf dem irgendwann Pflanzen wachsen werden. Da diese Pflanzen möglicherweise so dick werden, dass sie schließlich Schnee- und Windlasten aufnehmen, wollte ich mit LAR eine Flächenlast auf das Netz aufbringen. Ich habe dies bereits für Balkensysteme getan, aber ich erhalte eine Fehlermeldung (“keine tragenden Elemente [Balken] gefunden”), wenn ich versuche, dies für die Seilelemente zu tun. Das macht Sinn, da ich nur Seilelemente habe, aber ich frage mich, ob jemand eine andere Möglichkeit kennt, dies für Seilelemente zu tun. Das Kabelnetz ist extrem unregelmäßig, so dass die Anwendung einer Linienlast keine gute Annäherung ermöglichen würde, aber es ist mein Ersatzplan, wenn keine anderen Optionen möglich sind.
As far as I know, load distribution areas should work with cable elements. Please have a look at the attached SSD project. There you can see the program behaviour.
I was experiencing a similar issue as what Grant was experiencing, and found only this thread (and no other help). I wanted to post a “solution”, in case someone else has this error and finds this thread in the future.
In the Sofiload handbook, under CABL, it is explained that “loading on cable lements will be converted to nodal loads, as the element has no basic bearing capacity transverse to the cable”. Taking this idea to free-loading, it means that any loading defined using AREA (with a LAR) would be converted into point loads, loading the nodes of the cable elements.
I realised that within my LAR, there were no cable nodes defined, and hence no loads could be calculated for the load case (hence the error message).
So if you recieve this error message:
check the LAR in wingraf - to see if it is correctly placed on the structure
check that the cables are meshed with sufficient nodes for the calculation of point loads
Thanks for the reply! It’s been a while, but from what I remember, I tried defining an LAR over the entire cable net to see if I could get it to work at all, and I still think I was receiving the same error. I’ll try your approach if I get a similar project again.
I ended up solving my problem with a little bit of brute force by defining all of the loads by element. To do this, I imported the Sofistik mesh data into Rhino/Grasshopper and sorted the element numbers into the load regions I wanted. Would’ve been nicer if I could’ve done this with LAR, but it still worked fine.