Module 7 : Design of Machine Foundations
Lecture 31 : Basics of soil dynamics [ Section 31.3 : Different modes of vibration; Damped ]
   
 

If = 0, i. e. trivial solution.
So, nontrivial solution is,

 

Materials

Damping ratio ( ) values

Concrete

0.05 to 0.07

Steel

0.01 to 0.02

Aluminum

0.001 to 0.01

Soil

0.1 to 0.2

 

There are three possibilities,
Case 1) =


So,

Critical damping constant = (2m ),
Damping ratio ( ) = (c/ ). For different materials values are given in table 8.1.
Damped natural frequency ( ) = , where is the undamped natural frequency of the system.
 

Table 8.1 Different values of Damping ratio ( )
Note: For soil values are high i.e. soil is a good damper.

   
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