# Earthquakes and resonance

1. Feb 27, 2006

### bob4000

i have undertaken an investigation, where the aim is to establish a relationship between the frequencies of an earthquake, and the height of the building(at maximum deflection parallel to motion). to do this, a model was created; a building of lego blocks and a vibration generator set to reciprocate at frequencies 2,4,6,8,10 Hz (all frequencies investigated separately). the height at which maximum deflection was acheived was takes as the resonant point. the building started at 2 blocks, increasing in increments of 2 blocks each time. the deflection and height was then plotted. graphs were plotted to illustrate height vs deflection and frequency vs max deflection.

now how would i relate this to relevant physics theories/laws. it MAY not seem difficult to yourself, but it has baffled both of my teachers. the ones that I know we have to discuss are simple harmonic motion and resonance. but we have trouble applying even these to this investigation. how would i deduce any information/analyse from such graphs as mentioned above.

I AM NOT ATTEMPTING TO GET SOMEONE TO DO THIS FOR ME, JUST POSITIVE IN DEPTH GUIDANCE.

PLEASE E-MAIL ME AT surjmann2907@hotmail.com FOR ANY PROOF OF WORK DONE

Last edited: Feb 27, 2006
2. Feb 27, 2006

### Staff: Mentor

It seems like the first step would be to write the harmonic analysis equations for a finite thickness rod, or maybe a finite thickness rectangular tower in the direction of the flat faces.

Then the next step toward understanding a building's motion would be to perform a finite element analysis using a computer. In the simplest version, you could just use Excel to construct a 10-floor building with known masses, spring constants, dampings, etc. In a more complicated analysis, you could use existing FEA software, or write your own code. In the end, you should be able to correlate the experimental results with your FEA results, as long as you have modelled the physical situation well in your code.