topic Re: Problem with moving load combination in Robot Structural Analysis Forum

Problem with moving load combination

Anonymous — Mon, 11 May 2015 09:48:27 GMT

Hello,

So I have this problem with combining two or more moving loads, I couldn't come to a solution reading previous posts.

Model

I have severeal models of bridge section with two or more moving loads acting on it, and I want to make different combinations. The model has a steel bar structure with concrete slab, as a shell elements.

Problem

When I first made the moving loads, and a combination of them. I got envelopes for all three of the cases. Everything seemed fine, and the case numbering was correct.

When I changed the step, tried to combine new loads etc, RSA didn't calculate the combinations and I didn't get the envelope for my combinations.

Numbering

I've noticed that the numbering changes in a odd way when you recalculate moving loads, there was a post about this, but haven't been able to solve my problem with the information from that post.

My trials

So I want to change the step, I did this and the combination didn't work.

I made a new combination, it didn't work.

I remade the loads cases, it didn't work. (I deleted them in Analysis types).

I deleted the loads cases, opened the model in repair mode, remade all loads, it didn't work.

I made four load combination of two moving loads, two of them worked, one structural and one live combination.

I have tried a lot of things actually, but still I haven't figured out what i necessary to do in order to get combination to work.

My thougts

Since the model worked the first time, I think the problem is inherited from the "case numbering" that is created once the model is calcuted once with the combinations.

So I really want to be able to change the moving loads, and combinations. But I'm stuck, if there is a bug, a way around would suffice.

Re: Problem with moving load combination

Rafal.Gaweda — Mon, 11 May 2015 12:03:32 GMT

Not working file please.

Re: Problem with moving load combination

Anonymous — Mon, 11 May 2015 12:33:43 GMT

Yes,

I discarded the models I had problem with, but I tried to recreate the error. Of course, they did work. But those that haven't worked had step 0,5 and they take some time to calculate. I will email a model once i successfully created one with the error.

Re: Problem with moving load combination

Anonymous — Mon, 18 May 2015 06:53:43 GMT

Hello again,

I think the problem has to do with small steps for my loads, and the maximal number of combinations . Haven't actually solveded it, but I think that is why my combinations doesn't work. I will however not use that small steps, since it takes to long time to process the result part in my models, and I really don't need it.

I consider the matter closed 🙂