9 Replies Latest reply on Feb 4, 2009 12:24 PM by sandeep pawar

    Seismic load in Cosmos

    sagar bafana

      Hey everyone,

      I have made a supporting strucutre which comprises of different I-beams in SolidWorks. I am wondering how can I apply seismic load to that structure.

      Thanks for help

      Sagar
        • Seismic load in Cosmos
          sandeep pawar
          If you know how many 'g's the loads are going to be, both in vertical and horizontal direction, just goto Loads > Gravity and select the faces.

          If you have 3g, just add gravity 3 times

          Please correct me someone if I am wrong
          - Sandeep
          • Seismic load in Cosmos
            Nur Kholish Majid
            Hello All....

            Any body can clarify on how to apply seismic load in simulation ?

            @sandeep,

            g=gravity ???
            would you like to provice us some images ?

            Thanks
              • Seismic load in Cosmos
                Ameer Chilakala
                Hi,

                For doing the sesimic analysis in cosmos, as per my knowledge we need to do in Simualtion premium product i.e. mostly customer will give you g verses frequency curve, this input we need to apply in random vibartions.

                Mr. sandeep mentioned we need to give as a 3g, it means it will apply 3*9.81 m/sec2 load in static analysis, if the customer mentioning the loading is interms of g means this procedure may be right.

                if customer is giving g verses frequency curve means, as per my knowledge we need to do a random vibration.

                But in Simultion Premium 2009 while doing the random vibation it will not support the beam mesh. so may be we need to apply the 2g or 3g gravity load in static analysis.

                kindly let me know if i mentioned anything wrongly
              • Seismic load in Cosmos
                Arun Prasad
                Yes. I do a lot of seismic analysis for control valves. The values of `g` are generally specified by the customer as in OBE or SSE condition. We must know the values of g for horizontal and vertical directions.

                Let us assume, its 2g in horizontal and 3g in vertical direction.

                ie, 2*9.81=19.62 m/s^2 (horizontal) and

                3*9.81=29.43 m/s^2 (vertical).

                In Solidworks Simulation, start a static study-> go to External Loads -> Gravity.

                Here, selected reference plane must be Front or Right Plane. Apply the vertical gravity force(29.43 m/s^2) in the Earth`s gravity tab(Apple Icon) and then reverse direction. This completely defines vertical gravity.

                Similarly, Click advanced Tab, Apply horizontal force as in the desired direction(19.62 m/s^2).

                Actually, there is confusion with respect to the third direction. As safety is a prime concern in our industry, we apply
                horizontal force(19.62 m/s^2) again on the third direction. This may not be required. But, we apply the third direction force so as to protect the valve against possible failure. I mean, naturally, the FoS is increased.

                Why don't we theoretically verify this seismic load condition by solving some problem manually. Any Suggestion??
                • Seismic load in Cosmos
                  David Anderson
                  Hi,

                  If you are performing a seismic analysis on a structure, then there is a bit more to it than applying a static load.

                  I am delving in to seismic analysis' (using ANSYS) and ccording the the ASCE 07 handbook, seismic loads are given as g's vs t and are location dependant. because the g loads vary wrt to time you must perform a time history analysis to see how the structure responds to the inputs. this will require a nonlinear, rather than a linear solver.

                  a simple static load will tell you displacement and stress, but does not give response of the structure to a load that varies with time.

                  the base motion profile is dependent on location and looks something like the image attached for area code 90210.

                  check out

                  http://earthquake.usgs.gov/res.../design/#install_java

                  they have a neat little tool you can use to generate the seismic profile.



                  • Seismic load in Cosmos
                    Arun Prasad
                    Hi Sandeep,

                    See, I never told abt Face Selection. Its only Plane Selection.(Right/Front). See, when we stand on earth, there is gravity force that is pulling us downwards. Its not that gravity force is acting on our foot. Suppose we have a Solidworks Model of human body. If we restraint the base of the foot, how would you apply gravity? Which Face? or Which Part?

                    The gravity is acting on the body at CG(Center of Gravity) or Center of mass. So, we need to select the respective planes for horizontal or vertical gravity.

                    as an example, take the case of a pyramid with base fixed. Check the direction of plane on the screen shot
                      • Seismic load in Cosmos
                        Arun Prasad

                        Arun Prasad wrote:

                         

                        Hi Sandeep,



                        See, I never told abt Face Selection. Its only Plane Selection.(Right/Front). See, when we stand on earth, there is gravity force that is pulling us downwards. Its not that gravity force is acting on our foot. Suppose we have a Solidworks Model of human body. If we restraint the base of the foot, how would you apply gravity? Which Face? or Which Part?



                        The gravity is acting on the body at CG(Center of Gravity) or Center of mass. So, we need to select the respective planes for horizontal or vertical gravity.



                        as an example, take the case of a pyramid with base fixed. Check the direction of plane on the screen shot