I'm currently doing a small project in college for structures being damped. We're adding weights to a structure and measuring the damping affect. We've calculated the damping ratio and coeffecients, however, we currently have damping ratio increasing with mass, which I do not believe is correct following the below equation:

[![Equation for Damping Ratio][1]][1]


The above equation, assuming k and c are constant, suggests that zeta decreases as mass increases. 

However, the results we are getting are entirely different, and we do not have a constant value for the damping coefficient:

[![enter image description here][2]][2]

We got the initial value of damping ratio by interpreting the graphs by using the following equation and process: 

[![enter image description here][3]][3]

[![enter image description here][4]][4]

Where the above was rearrange from:

[![enter image description here][5]][5]

where 'n' = the number of full wave cycles between x_0 and x_n

Ultimately, I'm curious if the damping ratio should decrease with increase in mass, and should the damping coefficient stay constant?

  [1]: https://i.sstatic.net/jfP4r.png
  [2]: https://i.sstatic.net/uyL6t.png
  [3]: https://i.sstatic.net/Iqp0x.png
  [4]: https://i.sstatic.net/2rudd.png
  [5]: https://i.sstatic.net/7rVL2.png