Hi,
I am trying to apply a uniform distributed load on the top surface of a RC beam and hold the load in position. I am using MMALE solver for my simulation as my beam will loaded with a blast load later. I am currently using *Load_Node_Set keyword to apply the UDL on the beam. I am able to load the beam but unable to maintain the load on the beam. The load is able to hold for a few msecs but the load will eventually rise despite not setting the load to increase after certain value in the load curve. If you know how to set the loading, please advise me. Any help is greatly appreciated. Thanks.
Hi @saberman12,
Have you taken the number of nodes in the node set into account for the *Load_node_set? I believe that LS-Dyna will apply the load to each node in the set so you have to divide your load curve by the number of nodes. Just something that I've run across before.
Also make sure that your horizontal load curve is extended to the end of your simulation.
Let me know if either of these help.
Hi, thanks for replying. I am trying to apply a total of 600kN onto the entire top surface of my beam. There are a total of 875 nodes I am applying the force. Do you mean that the force I am entering in the keyword should be 865N?
Yeah, actually looks like it would be 685N. You can always create a *Database_cross_section_set through the column a couple rows of elements lower than that top and check the measured force just to make sure you are getting your desired force input.
As an alternative load condition, you could create a 2D rigid shell part that shares nodes with that top surface and apply *Load_rigid_body to that part and use 600kN as the load curve.
Thanks for the input. I am currently still unable to hold the loading on the beam. I know that my beam has not failed yet as I have loaded the beam with smaller loading but I am still facing the same problem. I cannot help but think that my loading method is incorrect. Many literature reviews use 3 or 4 point bending test to find the capacity of the beam but I have not found any paper using prescribe_motion_set or load_node_set to load the beam.
@saberman12 You mentioned bending tests, but you are trying to load the beam axially correct? Did you try the rigid plate method that I mentioned? Can you look at fringe plots to see this force reduction? Any images might be useful for us to help solve your issue.
I tried using the rigid plate method. However, as I am using MMALE solver because I want to apply blast load on the beam, the element formulation is not applicable to Mat 20 used for rigid material. I read from literature that I may have to do a full restart to split the blast stage and loading stage. Here is a picture of my beam.
