body forces and added mass

[Anonymous]

Hello, i have added some massies on my beams, and then added body forces to simulate waves. but i dont know if its right, can you see on it and give me a report on if its correct or not?

[Pawel.Pulak · Accepted solution]

I don't know what you wanted to model.

Analysing the file I can see what was really modelled, show my way of verification and point to possible mistakes.

I have attached the screen capture with 3 tables used during verification: the table of added masses, the table of load and the table of reactions. I have customized them to display only the necessary information, with sufficient number of decimals and in units easy to verify

Verification for load case 2

Total mass from the table of masses is 106011 kg.

As it can be seen in the table of loads the vertical acceleration of -1g is applied to added masses in load case 2 twice - by mistake?

That is why the sum of forces in the table of reactions for this load case is 2*106011 = 212022 kG (I have changed the units of force to kG to compare it easier).

Verification for load case 3

In this load case acceleration is applied to bars:

1to15 20to25 31 36 38 39 42to45 48 50 51 53 54 56to68

Above list extracted from the table of loads. It corresponds to all bars in the structure.

Total mass of these bars is 60025.44 kg (see sum of forces in the table of reactions for load case 1, i.e. selfweight). Acceleration of 0.356g, 0.556g and -0.20g in directions X, Y, Z respectively correspond to inertia forces:

0.356 * 60025.44 = 21369 kG in X

0.556 * 60025.44 = 33374 kG in Y

-0.20 * 60025.44 = -12005 kG in Z

These values are slightly different than corresponding sums of forces in the table of reactions for this load case because accelerations in X and Y are for bars 6 and 10 equal not to 0.356 and 0.556 but 0.36 and 0.56 respectively (marked in red in the attached screen capture) - which ones are correct? some mistake?

Verification of load case 4 analogous

0.36 * 106011 = 38163.96 kG in X

0.56 * 106011 = 59366.16 kG in Y

-0.2 * 106011 = -21202.2 kG in Z

Here I don't see any mistakes

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Regards,

[Anonymous]

Thank you so much 😄

[Pawel.Pulak]

You are welcome

Regards,