topic Re: Instability (type 1 and type 2) on a susended bridge in Robot Structural Analysis Forum

Instability (type 1 and type 2) on a susended bridge

mdesjardinsXJ286 — Fri, 28 Mar 2025 15:29:50 GMT

Hi,

I am new in robot. I modeled a cable bridge but I get instabilities at every connection between main cable and hangers. Anyone know how to fix this?

I uploaded structure file.

Re: Instability (type 1 and type 2) on a susended bridge

mdesjardinsXJ286 — Fri, 28 Mar 2025 15:33:24 GMT

Not able to load the file. Got this error message.

Re: Instability (type 1 and type 2) on a susended bridge

mdesjardinsXJ286 — Fri, 28 Mar 2025 15:39:39 GMT

Here is an overall view of the structure

Re: Instability (type 1 and type 2) on a susended bridge

Rafacascudo — Fri, 28 Mar 2025 16:59:23 GMT

zip it before attaching

Re: Instability (type 1 and type 2) on a susended bridge

mdesjardinsXJ286 — Fri, 28 Mar 2025 17:10:47 GMT

Here it is. Thanks for your help.

I am also getting incridibly high effort and displacement. Maybe I did some baisc error in the load attribution ?

Re: Instability (type 1 and type 2) on a susended bridge

Simau — Fri, 28 Mar 2025 23:14:05 GMT

Hi @mdesjardinsXJ286

Try this workaround:

Select cables CAB_S and set them as truss

Set case 1 parameter as image below:

Re: Instability (type 1 and type 2) on a susended bridge

mdesjardinsXJ286 — Fri, 28 Mar 2025 23:39:31 GMT

Thanks it worked.

I created a hanger section for the truss type and got this

Now I think I will just have to iterate a little bit to get exact curve and prestress for bridge inital stage.

If anyone have experience with modeling suspended bridge in ROBOT feel free to share any tips.