I want to know ,can I use the empirical formula time period T=0.1*N, where N = number of floors, to find the fundamental frequency of vibration of Tesla's laboratory building in which he performed experiment on the mechanical oscillator and the result of experiment was EARTHQUAKE!.. Through research I have found that his laboratory building was 7 story in the year1898 in New York city. I could not get any other details of the building. So I found time period using above formula which I found on Research gate site and took reciprocal of it to get the frequency. Is it correct?...Please reply. Here's the link showing image of Tesla's laboratory building. https://images.app.goo.gl/BTqpupmGp23s2BXB6

Best Regards.

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    $\begingroup$ Where did you get the empirical formula from. Please provide a link if possible. $\endgroup$
    – AJN
    Commented Jun 16, 2021 at 7:29
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    $\begingroup$ The formula doesn't make any phsyical sense IMO. Why would a 10-floor building have a first vibration mode 10 times higher than a 1-floor building? Any real-world experience with vibration engineering would suggest the opposite. $\endgroup$
    – alephzero
    Commented Jun 16, 2021 at 10:20
  • $\begingroup$ Oops, I was confused by the title (and the question) using "frequency" and "period" in the same sentence. The formula does make sense for the period (= 1/frequency). Not being a civil engineer, I would never use "period" to describe a vibration anyway :) $\endgroup$
    – alephzero
    Commented Jun 17, 2021 at 11:41

1 Answer 1


Yes, per the design code (ASCE 7 & IBC) the formula could be used for estimating the fundamental period of buildings during a seismic event if the construction of the building meets the criteria indicated in the code provisions.

enter image description here

See P 1-56, https://www.seismicreview.com/January_2017-Errata-1.pdf

However, as the seismic design and evaluation are quite involved, please check the latest IBC code and ASCE 7 for the "correctness" on using this approximate method to determine the building period for a specific application.

  • $\begingroup$ Thanks for this valuable information! $\endgroup$
    – sonali
    Commented Jun 17, 2021 at 10:01

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