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AutoPIPE Wiki 16. How is the Response Spectrum Analysis performed in AutoPIPE Vessel?
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            • 16. How is the Response Spectrum Analysis performed in AutoPIPE Vessel?
            • 17. How is the site spectrum resolved as static seismic loading in AutoPIPE Vessel?
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    16. How is the Response Spectrum Analysis performed in AutoPIPE Vessel?

    Answer. 

    A response spectrum analysis is run by using linear interpolation for the following site spectrum period and acceleration in the Earthquake tab under Vessel Properties>Load Conditions :

    Seismic code used in ASCE 7-2010.

     

    The analysis is run, the 5 modes and period are calculated as follows. The natural frequency is calculated by finite element beam stiffness matrix.

    The T=0.116 corresponding to which the spectral acceleration obtained from the site spectrum data is 0.238g which is obtained as follows:

    See the site spectrum table:

    The T=0.116 corresponding to which the spectral acceleration obtained from the site spectrum data is 0.238g which is obtained as follows:

     

    See the site spectrum table:

    Cs = Sa (since this is a response spectrum analysis) = 0.1 + 0.016 (0.28-0.23)/(0.2-0.1) = 0.238 g (by linear interpolation from the above table using period = 0.116) which is reported in the calculation report below:

    Once Cs is obtained, further calculations performed as follows:

     

    W=3,769.94 daN.(vessel weight for the design case)

     

    The base shear V=Cs x W = 0.238 g x 3769.94/g = 897 daN.

     

    Cvx obtained as shown in the report below, where wx is the weight of the section and hx is the distance from the datum:

     

    Fx = Cvx * V = eg. for section 12 , Fx = 0.00099 x 897 = 0.88803 = 0.9 as stated in the report.

     

    Fv = 0.2 x SDS x wx = 0.2 * (0.9g) x wx as in report, explanation as follows: (refer ASCE 7-10 par. 12.4.2.2)

     

    The vertical seismic load effect is a combination of Weight:

     

    so the Vertical Load Fv at each level is equal to 0.2SDS*wx (wx = weight at each level).

    Eg. for section 12: Fv=0.2 x .9 x 19.7 = 3.546 = 3.6 as in the report.

    • AutoPIPE Vessel
    • Response Spectrum
    • seismic
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    • Sudip Ganguly Created by Bentley Colleague Sudip Ganguly
    • When: Wed, Oct 7 2015 2:05 PM
    • JamieP Last revision by Bentley Colleague JamieP
    • When: Tue, Aug 25 2020 3:31 PM
    • Revisions: 4
    • Comments: 0
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