Moving load - accurate start and stop behavior 1

[PMR06]

Does anyone know of a way to "start/stop" a moving load in such a way that represents the physical extents the moving load would start and stop from. Currently the moving load just appears out of space and starts rolling down the structure, then rolls entirely off. In reality (a bridge crane for example) would be limited by the bumper stops.

Thanks in advance!

 

[JoshPlumSE]

Not sure I fully understand the question. Are you referring to the animation of the moving load, or the actual analysis? If you are referring to the animation of the moving load, then there is no way to prevent that.

If you are referring to the actual analysis and you want to terminate the moving load before it gets to the end of the beam, then just add in a joint however far from the end of the beam and end the moving load there.

 

[PMR06]

I am mainly referring to the analysis (the animation would just be eye candy). I think the moving load is set up for a scenario like a vehicle bridge, for example trucks or trains. In those cases, the vehicle wheels originate off the model, then start loading the modelled structure one at a time. Then at the other side of the model, the wheels "drive off" the modelled structure. However with something like a bridge crane, the wheels never "leave" the modelled structure. The starting and ending positions each have all 4 wheels on the structure at once (never 1,2 or 3 wheels only).

This isn't necessarily governing a design of mine, I just want to understand the feature as best I can...

Thanks again.

 

[JoshPlumSE]

Thank you for clarifying. Not sure why I didn't figure that out from your first post, maybe my mind hadn't yet turned on from the weekend.

That is correct, does assume the wheels roll off one by one. If your rear load is the maxi load, that could mean a higher than realistic shear at the end of the beam (because the rear load would never get that close).

If it were really important, there is a way to do this. You could specify each wheel load as a different moving load with a different start and end joint. Then apply them all at the same time. Certainly a bit of a pain, but it would accomplish the kind of analysis you want without the extra partial load conditions.

 

[JoshPlumSE]

Thank you for clarifying. Not sure why I didn't figure that out from your first post, maybe my mind hadn't yet turned on from the weekend.

That is correct, does assume the wheels roll off one by one. If your rear load is the maxi load, that could mean a higher than realistic shear at the end of the beam (because the rear load would never get that close).

If it were really important, there is a way to do this. You could specify each wheel load as a different moving load with a different start and end joint. Then apply them all at the same time. Certainly a bit of a pain, but it would accomplish the kind of analysis you want without the extra partial load conditions.

 

[PMR06]

Your multiple moving load idea is an interesting solution I hadn't considered. Actually it didn't take long at all to impliment... that would be the R in RISA again!

In my case the 4 wheel loads are equal, so I created a moving load pattern with single point load. Then I created 4 moving loads starting and ending at joints spaced at wheel spacing... worked exactly like I was picturing.

Thanks again!