topic Re: moving loads combination in Robot Structural Analysis Forum

moving loads combination

Anonymous — Thu, 31 May 2012 16:36:46 GMT

Hello!

I am trying to use moving loads.

First I am trying in a three spans beam. I defined a moving load with a concentrated load of 250 kN. I got the envelope of bending moments.

I don't know how to combine moving loads with the other actions??

Now I wat to combine moving loads with another actions like temperature and wind. When I made the moving load I got three load cases, the one that I created and one + and another -. But when I combined I can't use cases + and -, why??

Regards,

Gonçalo Sousa

Re: moving loads combination

Pawel.Pulak — Fri, 01 Jun 2012 08:36:59 GMT

Cases with + and - are additional load cases containing only top and bottom envelope values and automatically created for compound load cases, i.e. load cases containing many components.

Compound load cases are created in for instance the following situations:

1/ moving load case - many different positions of load

2/ automatic combinations - many different combinations

3/ time history - many time steps

4/ manual combination containing moving load case - many combinations for different positions of load

In your case you should combine the main moving load case (without + or -) with other loads. The manual combination defined this way will be a compound load case too (see point 4/ above) so it will be also accompanied by additional envelope cases with + and -.

In case of compound load cases the displayed components can be changed using Case component window.

See the screen captures below illustrating it:

- list of load cases for moving load case and manual combination containing moving load case

- component selection for moving load case

- component selection for manual combination containing moving load case

If you want to create combinations not for all positions of moving load but only for selected ones you can use "Create a case from component" for these selected positions of moving load and create combinations only with them.

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Regards,

Re: moving loads combination

Anonymous — Fri, 01 Jun 2012 11:04:04 GMT

Hi,

Thank you for your answer.

My problem is that in COMB1+ and COMB1- I can't see the results. In these combinations I should see the combination of moving load+ with DL1 and movingload- with DL1 respectevely???

Regards,

Gonçalo Sousa

Re: moving loads combination

Pawel.Pulak — Fri, 01 Jun 2012 14:50:38 GMT

Yes, it should be like in the attached screen capture.

Have you checked that moving load is correctly defined and it gives non-zero results in more than 1 position of vehicle?

Regards,

Re: moving loads combination

Anonymous — Tue, 27 Oct 2015 04:17:03 GMT

Project Info: I am structural design engineeer (BIC PVT LTD) and we are trying to analyse concrete slab on pretensioned i girders for 28000 mm span for urban metro project (elevated viaduct) .we have modeled the scenario using RSA 2014. The viaduct contains two tracks of metro train . In robot two moving loads have been deifined for each track respectively.

Problem : We want a combination of dead loads with with both of these moving loads acting together.Tried to make manual combination using two loads but no results were shown (results are displayed when only one moving load is combined with other NON-moving loads .).

How to view envelopes of loads containg both moving loads along with other actions

Re: moving loads combination

Anonymous — Thu, 10 Dec 2015 09:23:42 GMT

I am having the same problem as the above post.

I have a structure with 6 moving cranes. I want to consider all cranes operating simultaneiously. I created a combination with the following cases:

61 Crane 1

62 Crane 2

63 Crane 3

64 Crane 4

65 Crane 5

66 Crane 6

This is 10001 COMB1 - when I run the analysis, there is no "COMB1 +" and "COMB1-". But when I only have 1 moving crane in a combination, it will give me the + and - combination.

Help please Artur/Rafal 🙂 !

Re: moving loads combination

Rafal.Gaweda — Thu, 10 Dec 2015 09:29:53 GMT

File please.

Re: moving loads combination

Anonymous — Thu, 10 Dec 2015 09:55:52 GMT

https://www.dropbox.com/s/l3vs1ltyykjj55y/Test%20Model.rtd?dl=0

Re: moving loads combination

Rafal.Gaweda — Thu, 10 Dec 2015 10:26:05 GMT

As far as I can see you want to generate 71640450 combinations, but default limit set in job preferences is 64000. Change it and check.
I have never tried to generate so many combinations.

Re: moving loads combination

StefanoPasquini6790 — Thu, 09 Mar 2017 09:34:59 GMT

Dear all,

I've a problem with manual combination with moving loads in a bridge with 4 different lanes with 4 different moving loads. As far as I can see, I'm able to do a manual combination for only one moving load, if I add another "moving load case" the combination is empty of results.

Which can be the solution??? Do I have to create a vehicle with the 4 lanes simultaneously?????

here you can find the draft model.

Cheers and thank you in advance, sorry if I ask you a banal question, but I don't design bridges everyday!!!!!!

Re: moving loads combination

Artur.Kosakowski — Thu, 09 Mar 2017 11:33:31 GMT

I'd consider the following approach:

1. Generate components (positions of the vehicles) for all 4 moving loads

2. Convert the them into simple loads cases

3. Group them into 4 groups with OR (EXCL) operator among cases for the same vehicle in automatic combinations dialog

4. Run automatic generation of combinations

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Re: moving loads combination

StefanoPasquini6790 — Thu, 09 Mar 2017 14:11:49 GMT

Hi Artur and thank you for your answer, I've done as you said, but the number of combinations is incredible, so....

I've generated all the load cases from the moving loads, then I've edited the load table in excel grouping the load cases using the criterion of the load position. This way I have only 54 load cases instead of 162....it seems that it works...

Now my next step is to double the load position distance, from 1 meter to 2 meters, so that the load cases will became 27....

I let you know my results, Cheers

Re: moving loads combination

Artur.Kosakowski — Thu, 09 Mar 2017 14:20:16 GMT

Perhaps you can use the influence lines to determine the least favorable positions of the vehicles for given design elements and create combinations in this way?

Re: moving loads combination

Rafacascudo — Thu, 09 Mar 2017 22:14:30 GMT

Hi Stefano ,

I managed to combine all you 3 moving load cases ,through combination tables ,and it seems to be working nice.

changed the step to 3 meters.

Not really sure if it was this you were looking for.

Anyway , finding the worst places toplace the vehicles is also a good option as Artur pointed out.

In your case is the Load Pattern feature ( influence surface )

model with combination attached. saved without results

Re: moving loads combination

StefanoPasquini6790 — Sat, 11 Mar 2017 14:07:55 GMT

Thank you Rafa,

this is not exactly what I mean, but it works perfectly.

Sorry if I'm replying you so lately, but I was in Norway for a design competition and there I was not able to open your model.

Cheers a thank you again

Re: moving loads combination

Artur.Kosakowski — Mon, 13 Mar 2017 09:51:59 GMT

Hi Stefano,

I was in Norway for a design competition

Knowing what you can do I think I may congratulate you on winning the top prize

All the best.

Artur

Re: moving loads combination

StefanoPasquini6790 — Mon, 13 Mar 2017 10:30:37 GMT

Thank you Artur,

I will know the results in two weeks, I'm sure that it will be impossible to win because my opponents are incredibly famous worldwide design firm....anyway we are in final!!!

I will let you know the results.

Cheers!

Re: moving loads combination

Artur.Kosakowski — Wed, 17 May 2017 10:32:59 GMT

@StefanoPasquini6790

I just wanted to ask for the final result

Re: moving loads combination

Rafacascudo — Wed, 17 May 2017 11:30:35 GMT

he came in 2nd place . Lost to Benoy by 2 points only!!!!

http://www.benoy.com/

Re: moving loads combination

StefanoPasquini6790 — Wed, 17 May 2017 11:57:23 GMT

Yes it is......I'm still desperate for this result, but it's like to loose versus Real Mardid!!!!!

I will send you privately our presentation.

Cheers.