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Re: Pier Natural Frequency

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I have been using the following equations for seismic load application to
develop many types of elevated water tank design programs.

Natural Frequency, w = SQRT(K / Mass) = SQRT[K / (W/g)] = SQRT(Kg / W) in
Radians / sec.

Where, K = Spring constant = P / defl.  in kips/in  (The load that produce
a unit deflection at C.G.)

             g = Acceleration of gravity = 386 in/sec^2 = 32.2 Ft/sec^2

             W = Total weight of pier and machine in kips

Natural Period, T = 2(pi) / w = 2(pi)SQRT(W / Kg) = 2(pi)SQRT(W / 386 / K)
=- 0.32 SQRT(W / K) in seconds / cycle

T.J. Fu



                                                                                                                               
                      "Rich Lewis"                                                                                             
                      <sea@lewisenginee        To:       <seaint(--nospam--at)seaint.org>                                                   
                      ring.com>                cc:                                                                             
                                               Subject:  Pier Natural Frequency                                                
                      12/28/2004 12:17                                                                                         
                      AM                                                                                                       
                      Please respond to                                                                                        
                      seaint                                                                                                   
                                                                                                                               
                                                                                                                               




I have a requirement to have a cantilever pier supporting a machine to have
a natural frequency greater than 50 Hz.  How do you calculate the natural
frequency of a cantilever pier?



Rich Lewis
Lewis Engineering










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