topic Re: Variable step moving load in Robot Structural Analysis Forum

Variable step moving load

Anonymous — Thu, 21 Feb 2019 15:30:45 GMT

Hello, i have a moving load which should be applied to bars which are perpendicular to the path of said load. The spacing of these bars is not constant, and i would like each step to represent the load being applied only to one of the bars. Is there a way to define a variable step for moving loads?

I have managed to apply the loads on these bars by checking the "vehicle position at the points of the polyline" box but RSA still creates additional case components with 1 m spacing. If this spacing cannot be altered, is there a way to delete case components which represent the load being applied in the middle of two bars?

I attach a screenshot of one component in which the load is being applied at a intermediate point (one of the ones i would like to delete)

Re: Variable step moving load

Artur.Kosakowski — Thu, 21 Feb 2019 15:43:40 GMT

Hi @Anonymous

You can convert generated positions of vehicle into single load cases and then delete the 'excessive' ones but I'd satrt with setting the steps as a high value:

If I managed to answer your question(s) press the Accept as Solution button please. This will help other users to find solution(s) much faster. Thank you.

Re: Variable step moving load

Anonymous — Thu, 21 Feb 2019 16:20:03 GMT

Thanks! I changed the step to a distance longer than the length of the path and it worked just fine.

I also get the "no convergence of nonlinear problem" which i did not get before entering the moving load. My structure has "truss tension" members so i had to enter combinations manually but it worked until i entered the moving load. Any ideas about what might be happening?

Thank you very much again for the rapid response

Re: Variable step moving load

Rafacascudo — Thu, 21 Feb 2019 19:42:18 GMT

On nonlinear parameters, mark to update matrix after each iteration

Re: Variable step moving load

Anonymous — Fri, 22 Feb 2019 08:35:35 GMT

Thanks @Rafacascudo, that did work! i had changed it already on all load cases except the moving load ones, as soon as i checked it it worked.

Re: Variable step moving load

Anonymous — Fri, 22 Feb 2019 09:07:37 GMT

@Artur.Kosakowski @Rafacascudo

Just one last thing (i hope)

My moving load has concentrated loads on all 3 directions. I have managed to apply them by multiplying the vertical load using the "coef HL/ HR" and "coef VR/VL" columns on the route parameters. However, my route has 8 points and there are only 7 lines on that table. The strangest thing is that when i see the applied loads it applies the same loads on the last step, only that it changes the direction of one of them.

I attach pictures of the second last step and the last. As you will see the FX load changes direction on the last step (8th step) from 14.18 to -14.18 and viceversa on the simetric point. This step doesnt correspond to any line of the route parameters table (also attached).

Thank you again for your very helpful comments.

Re: Variable step moving load

Rafacascudo — Fri, 22 Feb 2019 12:51:06 GMT

1- try creating one more segment and see what happens

If it doesn´t work

2- Create load cases from moving load components and edit the wrong load manually

Re: Variable step moving load

Anonymous — Fri, 22 Feb 2019 12:58:51 GMT

Thanks again for the help, i ended up creating additional cases for each position and combinating them manually, because i couldnt combinate 2 moving loads easily.