I have not understand your reply...i'm speaking about phase sign in the formula by Caesar manual, not damping...

the test for looking at the sign of phase for a rotating displacement is quite simple.

1) created a simple system, starting at node 10

2) applied the following harmonic displacements at node 10:

frequency 50Hz

displacement 0.5", dir. Y, phase 0

displacement 0.5", dir. Z, phase +90

3) run harmonic analysis with the following displacements results at node 10

CASE 2 (OCC) 50.0000 Hz 0.00

CASE 3 (OCC) 50.0000 Hz 80.00

CASE 4 (OCC) 50.0000 Hz 180.00

CASE 5 (OCC) 50.0000 Hz 280.24

CASE 6 (OCC) 50.0000 Hz 340.00

Node Load DX in. DY in. DZ in. RX deg. RY deg. RZ deg.

10 2(OCC) 0.0000 0.4982 -0.0299 -0.0000 0.0000 0.0000

10 3(OCC) -0.0000 0.1160 0.4854 -0.0000 -0.0000 0.0000

10 4(OCC) -0.0000 -0.4982 0.0299 0.0000 -0.0000 -0.0000

10 5(OCC) 0.0000 0.0591 -0.4956 0.0000 0.0000 -0.0000

10 6(OCC) 0.0000 0.4579 -0.1985 -0.0000 0.0000 0.0000

my interpretation is that at 0 (omega t) the combined displacement is in direction +Y, at 90 is in direction +Z, at 180 in direction -Y, at 270 in direction -Z (360 in direction +Y again)

therefore I've simulated at counterclock wise rotation around X axys (CCW looking to -X).

therefore the displacement in Z direction must have the form A*cos(wt - phi).

the correct sign in the formula for the phasing angle is MINUS.

When the user insert a +90 phase angle in the input dialog of harmonic analysis of CII, the wave applied by the software is A*cos(wt - 90) ... not A*cos(wt + 90) as, I think, all users can imagine (because it is the normal formula)

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*Edited by Lido (TCS) (12/10/19 10:54 AM)*
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Lido

TCS Eng.