9 Replies Latest reply on Mar 15, 2010 1:01 PM by Pete Yodis

    Finding Forces

    Romy r
      I have made an analyze with solid mesh because with beam mesh or mixed mesh didn't work.
      But anyway, I would like to find the forces that are acting to the deck, trough the pillars.
      I have attached a picture. I would like to find the values for F1, F2, F3, F4.
      Can this be possible?
      And if it is can somebody explain how?

      Thank you
        • Finding Forces
          Pedro Nunes
          I think that you can supress the ship deck and apply restrains in the faces that made contact between the ship deck and the welded frame, run the analyze again and then right click on the results folder, and select List Result Force.

          Good Luck
          • Finding Forces
            Fernando Cuenca
            What Pedro describes would be a good approach, but you should know that reaction forces aren't calculated through FEA, they are just calculated doing a free body diagram and enforcing equilibrium. This structure is simple enough to do it by hand in my opinion.

            Now if you take the deck into account and it deforms significantly you may want to set up a no penetration contact between the pile and the deck and find out the contact forces.
              • Finding Forces
                Pete Yodis
                Cosmos Motion can also be used to determine the reaction loads at your joints. Don't know if you have the software or not - but this could quickly be done without the overhead of meshing/solving and with Cosmos Motion it would be much faster than solving by hand. Of course you could solve by hand and compare it to the computed answers. Once the loads are determined in CosmosMotion, they can be exported quickly into a static FEA study. Very nice.
                  • Finding Forces
                    Pete Yodis
                    There is an example in this demo of exactly what you are trying to do using Cosmos Motion...


                    start watching at the 38:30 minute mark.
                      • Finding Forces
                        Vince Adams
                        Great discussion! I would caution against replacing an attachment to an elastic body with restraints for the purposes of extracting forces. Since the restraints are perfectly rigid and you can see that the deck is sharing the energy of the deformation, the forces will be very different using restraints vs. a bond.

                        Your best bet is to use the Free Body Forces tool that was put in as of 2007. You can query the forces across the bond between the components as they are calculated in the model you showed.

                        In 2007, you had to enable these in the Study Properties before the run. In 2008, they are turned on by default.

                        Good luck!!

                          • Finding Forces
                            Huy Nguyen
                            Free body forces across the bonded contact are not correct, however. This issue is for 2008 sp 3.1

                            Huy Nguyen, P.Eng

                            Forum | Vanoil
                              • Finding Forces
                                Andrey Aliamovskiy
                                Look at the
                                  • Finding Forces
                                    Huy Nguyen
                                    Whether definning a bonded contact explicitly or definning using find contact faces produces identical results. The magnitude of the free body force is still not correct. A hand calculated free body diagram of internal force across the bonded section reveals this discrepancy. I have sent in a simple model to demonstrate this issue to cosmos tech support. I am still waiting for a response from them. This issue has influenced previously analyzed 2007 and 2008 (up to sp3.1) results if accessed by 2008 sp3.1 version; however, 2007 (up to sp5.0) version has no issues with free body force calculation.

                                    Huy Nguyen, P.Eng.

                                    Forum | Vanoil
                                • Re: Finding Forces
                                  Pete Yodis



                                       Hope you don't mind dragging this topic back up, but something here at my company has come up that loosely relates to this topic.  I think what you are saying is that a completely rigid support will give different answers compared to support that has an amount of deformation to it.  Is that what you are saying here?  Would the forces reported by the simulation more closely match reality if the supports are allowed to deform versus if they are completely rigid?  If that is the case, then would completely rigid supports give reaction forces that are always higher when compared to supports that are allowed to deflect (have some finite stiffness)?  Any light you can shed on this would be much appreciated.