moses connection problem

How would I set up the model if I want to pass the two boats in the picture through the front truss articulated together?

Looking forward to your reply ,thank you

zjang

Parents
  • Hi Zhang,

    You can utilize the MOSES GSPR connector class to define the truss end connections to the boats by providing the stiffness values (x, y, z, rx, ry, rz) according to your connection properties. You will need to define the truss as a separate body and specify the endpoints that are connected to the barge. If the truss is just resting on the barge, then you can use the compression-only GSPR element. If it is tied to the barge, then you can use both the tension/compression GSPR class. The way you define the connection stiffnesses will entirely depend on the type of connection (welded, pinned, resting, etc.). Based on this, you can release some degrees of freedom depending on the type of connection.

    If connector forces are not your concern, you can also define it as a restraint class. I suggest you read section 13 of the manual to learn about "connections and restraints." Please let me know if this is helpful or if you need further assistance.

    Regards,

    Rahul Kanotra

  • Hi  

    This is the model I set up by referring to the help document. Can you help me take a look and modify the error code in the model?

    My Google email is zjang19970808@gmail.com

    Thank you  

    171.rar

  • Hi Zjang,

    In order for me to help you, you will need to explain what you are trying to accomplish. I saw your files, and before the stability_ok macro, I noticed that the barges are in the following configuration (shown below). Also, your system consists of three bodies (barge1, barge2, and HENGJIA), and then you are attempting to run stability analysis for multiple bodies in the same files.

    Are the two barges rigidly connected to each other through the truss and H-shaped steel structure? By rigid, I mean is the relative movement of the barges constrained due to the connecting structure? Are you then trying to perform stability analysis of the entire system (2 barges + Truss)? In that case, you will need to define them as a single body and not as three separate bodies. Also, in that case, you will not need to define the GSPR connectors since now all three units (parts) belong to a single rigid body. Once you have defined this single body, you can then perform the stability analysis using the stab_ok macro as used in your files.

    I hope the above is clear. If this is not what you intend to do, then please lay out clearly what you are trying to accomplish, and I can further advise.

    Regards

    Rahul Kanotra

  • The two ships are hinged together through trusses, and the H-shaped steel structure above simulates the transported cargo.

    I want to try to calculate whether the connection stiffness has an impact on the stability when there is a certain relative motion between the two ships?

    Just like the picture below

  • Hi Zjang,

    Your question is still not clear to me. When you mention the impact on stability, what kind of impact are you referring to? The stability of a barge is influenced by hydrostatics (hull form), load distribution (KG), and heeling moment due to external forces (wind, waves, etc). While you cannot perform a multibody stability analysis in MOSES (or any other software), you can conduct a stability analysis for a single barge with cargo. In that case, you can model half the weight of the truss/h-shape and appropriate ballast and check if it satisfies all the stability requirements. Half the weight is considered because it is shared between two barges. However, this advice is based on my understanding, and you, being familiar with your problem, should apply your engineering judgment. The most crucial aspect is to clearly define the problem.

    Let me know if you have further questions.

    Thanks,

    Rahul Kanotra

Reply
  • Hi Zjang,

    Your question is still not clear to me. When you mention the impact on stability, what kind of impact are you referring to? The stability of a barge is influenced by hydrostatics (hull form), load distribution (KG), and heeling moment due to external forces (wind, waves, etc). While you cannot perform a multibody stability analysis in MOSES (or any other software), you can conduct a stability analysis for a single barge with cargo. In that case, you can model half the weight of the truss/h-shape and appropriate ballast and check if it satisfies all the stability requirements. Half the weight is considered because it is shared between two barges. However, this advice is based on my understanding, and you, being familiar with your problem, should apply your engineering judgment. The most crucial aspect is to clearly define the problem.

    Let me know if you have further questions.

    Thanks,

    Rahul Kanotra

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