The Rayleigh damping model is an approximation to viscous damping. It allows modeling the energy dissipation in the material due to internal friction, assuming it is proportional to the strain or deformation rate. It is common to be in the need to determine the model coefficients from experimental or assumed data. We will explore the definition to determine the Rayleigh damping coefficients. For large degrees of freedom systems, it is difficult to guess the values of Rayleigh damping coefficients α and β. There are a number of general purposes available that have the provision of providing the value of α and β for calculation of Rayleigh damping matrix for dynamic analysis of systems with multi-degree of freedom. Since a designer may not be in a position to pre-assess the same at the beginning, has no option but to assume an unrealistic constant damping ratio for all modes. Based on the present technology it is very simple to develop a spreadsheet and arrive at a rational value of α and β which produces a damping ratio sequence increasing progressively with each of the subsequent modes and one can furnish input data for the dynamic analysis. The present report outlines a procedure that ensures a rational estimate of α and β even for a system with significant degrees of freedom. The results obtained have been as a real value for The Rayleigh damping model.

Rayleigh, damping coefficients, time-history analysis, calculation, response spectrum, FEM, directs method