| Notetip |
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Modal response spectrum analysis specified in 12.9.1 is done automatically. |
| Notetip |
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In accordance with 12.9.1.1, the sufficient number of vibration modes to be taken into account is calculated automatically as 90%. |
| Notetip |
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With the modal response analysis, seismic effects are combined automatically by CQC. |
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Modal analysis provides the entire response history for a given ground motion record. For design
purposes, its application requires a design ground motion record that is representative of the seismic
hazard at the site. for For design purposes, we usually use the maximum value of a response parameter and
not the entire response history. Since every mode can be treated as an independent SDOF system, the
maximum response values of a mode can be easily obtained from the corresponding response
spectrum. If Sd(Tn, x), Sv(Tn, x), and Sa(Tn, x) denote the spectral displacement, velocity and acceleration,
respectively, the maximum modal displacements are obtained from a response spectrum as
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The maximum displacement and the equivalent lateral force of the jth jth storey
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It is used in the horizontal elastic design spectrum in the direction of a given earthquake and the maximum values of the response magnitudes in each vibration mode are calculated with the modal analysis method. The largest non-synchronous modal behavior magnitudes calculated for enough vibration modes are then combined statistically to obtain approximate values of the largest behavior magnitudes.
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