Page 58 - Dynamic Loading and Design of Structures
P. 58
(2.35)
It should be noted here that the coefficient of damping βis seldom used nowadays, with
preference given to damping ratio . Obviously, the two coefficients are related as
The effect of damping on the natural frequency is minimal; for instance, a 10 per cent of
critical damping ratio yields . It is rare to find civil engineering structures
exhibiting anything close to critical damping, although many mechanical components (such as
shock absorbers) do.
Damping can be experimentally measured by tracing the logarithmic decrement (i.e. the log
of the difference between two consecutive peaks in a displacement versus time plot for free
vibrations). Referring to Figure 2.10, we have the logarithmic decrement as
