Two moving loads acting simultaneously

[PedroBiel]

I have a structure which supports a machine, this machine has a chute and this chute can be clogged. Translated into RSA, I have two load cases as moving loads, one the machine itself, the other one the clogging of the chute.

I have two doubts about the generation of this model:

1. According to the calculation rules the load of the clogged chute is defined as extraordinary load. The question is how can I define the moving load 'clogging of the chute' as extraordinary load? (Machine and clogging are factored with different coefficients depending on the combination case)

2. The machine and the clogging load act simultaneously, that means both moving loads take the same position. How can I define two moving loads which act simultaneously in the same position?

Thank you

[Artur.Kosakowski]

You can always convert positions of the moving loads into simple load cases and create the appropriate combinations. This should work for all possible scenarios. On the other hand if you don't need SLS combinations then you may try to define a vehicle that contains both loads (machine and chute) with values of loads already with the corresponding load factors and use 1.0  load factor for moving load  in definitions of combinations.

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[PedroBiel]

Hi, I'm busy these days with other matters too and I don't have all the time for this question. Your advice was enlightening for me, I have the solution but not exactly as you tell me. The point is that apart from the machine and clogging of the chute I have seismic loads too. I can't afford to convert all the moving loads in simple cases, apart from the slowdown of the calculation time, it would take me hundreds of days! Instead, I have created manual combinations (menu Loads -> Manual Combinations...) with the moving loads according with the standards and seems to work.

I'm waiting to finish the calculation to show in the forum the results and let other users take advantage if the case arises, but that would take me still some days.

[Artur.Kosakowski]

It is nice to hear that you managed to solve the issue 

[PedroBiel · Accepted solution]

The work is done!

I have created two models in order to study both solutions for a metallic lattice. One of them has bars working in tension, in the other one the bars are working only with axial forces (advanced properties).

In the first lattice I did what you said, the bad side is that I actually had six different moving loads (machine, machine whit seismic in every direction and machine with clogging in the chute) and it took time and care to convert the moving loads into simple load cases.

In the second lattice the calculations were made as I told in my last post, I created manual combinations with the moving loads, which is much faster than the other method.