I would like to calculate the spring constant of a frame structure. I thought that I could do it like this:

  1. I apply a point force on the structure: enter image description here

  2. Then I calculate the displacement at that same point: enter image description here

Finnaly, I asume that the material bends within its elastic limit: $k=\frac{F}{\delta_y}$

Question1: Do you agree with this method ?

Question2: If I have a different type of loading, for instance a distributed load, would the spring constant change ?


Yes it would change.

For example same load if applied at quarter span would cause less deflection and a different curve.

Hence bigger K.

basically for the type of loading you display applying the load at center corrolates to smallest K.

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  • $\begingroup$ Thank you for your response. If I apply a continous loading (pressure) how can I find the spring index? Do you know? $\endgroup$ – james Mar 25 '18 at 6:19
  • $\begingroup$ For continius loading say same load as previous one : P if spread over all or part if span, will cause less deflection so the K would be bigger. $\endgroup$ – kamran Mar 25 '18 at 14:18
  • $\begingroup$ I see. How do you calculate k ? Do you use the equivalent force at applied to the centroid of the continius loading ? $\endgroup$ – james Mar 25 '18 at 14:27
  • $\begingroup$ I would use something like Hardy- Cross method to quickly calculate the frames stresses and deflctiins. $\endgroup$ – kamran Mar 25 '18 at 14:30

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