14 Replies Latest reply on Jun 8, 2015 3:18 PM by Michael Kalin

    Static Simulation beam analysis

    Madhav Rale

      I have to perform a benchmark simulation for a customer. The customer manufacturers steel frames (racks) on which stuff is kept. The customer wants to ensure when in uneven loading the rack wont tip over because of the weight of the articles kept on it. Is this possible in static analysis? A few tips on the required settings if yes.

       

      Thank you

        • Re: Static Simulation beam analysis
          Jared Conway

          "the rack won't tip over" how will you evaluate this as that is no longer a static case?

           

          this would be more of a motion problem or you could use a static analysis and evaluate the reaction forces (like you would in a free body diagram)

          • Re: Static Simulation beam analysis
            Madhav Rale

            Thanks Jared..I am thinking I can use the hinge fixture to some effect here? I cannot use motion as the racks are all beams. If I use the hinge fixture to two ends (legs) of the rack frame which will all be on a solid floor (so hinges between the two legs and the floor) and use a force on the diagonally opposite end of the table on some surface going upwards...what can I get out of it? Some more insight or anything on how I can go about this will be greatly appreciated.

             

            Thank You

            • Re: Static Simulation beam analysis
              James Riddell

              You don't even need simulation to do this you can perform the same analysis in modeling.  All you have to do is to unevenly load the rack and have the software evaluate the CG of the assembly.  If the CG is outside the footprint of the structure then it is unstable and will fall over.  If it is 'close' then it is fairly simple to calculate how much of a 'bump' would send it over.

                • Re: Static Simulation beam analysis
                  Theo Linders

                  isn't it possible to calculate your centre of gravity in the assembly and see where it is positioned?

                    • Re: Static Simulation beam analysis
                      Madhav Rale

                      Yes but apart from the location I would no nothing. Also for all things kept on the rack which fit within the boundaries of the rack (do not jut out) the CG displayed will be located inside the body (bodies) itself. I am trying to find out if it will tip over due to excess loading.

                        • Re: Static Simulation beam analysis
                          James Riddell

                          You can still figure out your over-turning moment in a simple hand calculation.

                           

                          On another note; you show the base 'encastre', it's very unlikely that it is evenly glued to the floor.  You should be restraining from the bolt locations.  Also, are the legs 'bonded' to this plate in your model (or reality)?  If so, that is another kettle of fish.

                           

                          What is the expected mode of upsetting force?  If seismic then you should be applying the appropriate amount via shear load at the top in all orientations.

                           

                          Again, if nothing is overhanging and the CG stays within the boundaries and there is no external force then the structure is statically stable.  Calculate first then verify with the appropriate FEA model if necessary.  Don't over-complicate the process.

                            • Re: Static Simulation beam analysis
                              Madhav Rale

                              Thank you James for your input.

                              The base is the floor modeled basically. I have used no penetration contacts between the four legs and the floor. And have used a hinge contact at the hinge that I have modeled. This set up so that I can simulate the table/rack toppling over.

                              The upsetting force will be the self weight of the items loaded on the rack. If the user loads too much at one end and nothing at the other a moment should be generated and cause it to topple over. I am not interested in any other mode of upsetting force.

                              Also as an applications engineer I am trying to benchmark a method to show the customer that this can be done in Solidworks and thus sell them a seat! So hand calculations are out of question I need to show the customer that the software is capable of doing it for them.

                                • Re: Static Simulation beam analysis
                                  James Riddell

                                  Madhav,

                                  I think you just answered your own question - to wit: it's a sales issue.

                                   

                                  However, you have modeled it incorrectly and likely you have applied the forces incorrectly.  I would model it as if the feet were on the floor, simply supported in the vertical case only with an edge restraint on the 'far' side in the horizontal, and add a 'bump' force near the top such as might happen with a forklift hitting the rack.  You'd need to run that in non-linear since your displacement would exceed the capability of static calculations.  No need to add the complexity of a hinge either since you are looking for excess deflection and (as mentioned before) static analysis assumes minimal deflections.

                                   

                                  jr

                        • Re: Static Simulation beam analysis
                          Theo Linders

                          What is wrong with the simple handcalculation of the tilting moment and compare it to the holding moment?

                          • Re: Static Simulation beam analysis
                            Michael Kalin

                            I agree with Jared, run it as a motion study. While motion cannot do beams, it also does not need to mesh with tets, so thin members like that are not as much of an issue. Define what mates you need, contacts between the legs and the floor, and forces, just as in static, and run with a motion analysis. I've done this in the past for applications where the customer was concerned that a hanging load over thin legs would result in tipping.

                             

                            While non-linear can do it, the simulations take some time, and you are using an extremely advanced tool for a very simple problem. Also note that motion analysis is in the SAME PACKAGE as static, so your sales person has nothing to complain about.