I have a question regarding the determination of the mass and stiffness damping parameters of Rayleigh Damping. In Plaxis, we need to input the target frequencies and damping percentage to calculate the mass and stiffness damping parameters. So, I have used 5% damping for concrete and target angular frequencies 0.557 and 3.49189 from calculations of Rayleigh damping parameters (for c/s area 3X1.5, M30 grade concrete). However, despite using these values, Plaxis3D self-adjusts these values.
Dear Shreya, once you input the required parametres of target 1 and target 2, the software will calculate "Rayleigh alpha" and "Rayleigh beta" values. So no matter re adjusted values in the display, "Rayleigh alpha" and "Rayleigh beta" should remain the same. This issue has been discussed many times by Dennis waterman and Stopoulos. Just at the forum type, Rayleigh damping you will find detailed explanations.
For instance: RE: Hi I have two questions. Would you please help me with? 1) I wanna change the first and second frequencies to find alpha and beta, automatically by the software. The problem is that when I change f1 and f2, click on OK and again open the properties box