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Basics of Earthquakes

Basics of Earthquakes. Frequency. Pendulum: Swings at a frequency of one vibration per second = 1 Hz = Period of 1 sec. Basics of Earthquakes. Frequency. [ C D E F G A B ]. Piano - Note C = 128 times per Sec = 128 Hz. Basics of Earthquakes. Frequency.

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Basics of Earthquakes

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  1. Basics of Earthquakes Frequency Pendulum: Swings at a frequency of one vibration per second = 1 Hz = Period of 1 sec

  2. Basics of Earthquakes Frequency [ C D E F G A B ] Piano - Note C = 128 times per Sec = 128 Hz

  3. Basics of Earthquakes Frequency 10-story building - Pull the top to one side and release it = ??

  4. Basics of Earthquakes Resonance is when motion at a given frequency is amplified by waves of that same frequency

  5. Basics of Earthquakes Single degree of freedom (SDoF) oscillator Natural Frequency, fn, Where,fn = Natural Frequency (Hertz ) or (No. of Cycles/Second)k = Element Stiffness (N/m)m = Element Mass (kg) Radian frequency, ωn = 2π fn

  6. Strong Ground motion • Accelerations between 0.001 and 2 g • Frequencies between 0 to 100 Hz.

  7. Basics of Earthquakes • Branch of Structural Dynamics Simplified SDOF ‘equation of motion’ f(t) = ma + kt + cu Or’ f(t) = cu + ků + mϋ ů = du / dt ϋ = dů/dt F = Shear Force m = Mass k = Stiffness c = damping coefficient a = acceleration T = time period u = displacement

  8. Analysis • Depends on ‘type of building’ and ‘extent of needs’ • Types • Static • Dynamic • Names such as • Equivalent load / Linear Static • Time history / Linear Dynamic • Response spectrum / Pushover / Non Linear Static

  9. Basics of Earthquake resistant Construction Look to Ensure • Proper Design • Architectural • Structure • Construction quality • Coordination between agencies, and clarity of roles • Intelligent solutions such as • Base Isolation • Flotation

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