Symbols
T = Natural vibration period [s]
T A = Horizontal elastic design acceleration spectrum corner period [s]
T B = Horizontal elastic design acceleration spectrum corner period [s]
S ae (T) = Horizontal elastic design spectral acceleration [g]
S aR (T) = Reduced design spectral acceleration [g]
D = Cd = StrengthReductionCoefficient
Ie= Building Importance Coefficient
R = Structural System Behavior Coefficient
R a (T) = Predicted ductility capacity and period dependent Earthquake Load Reduction Coefficient
4.4.1. Design Acceleration Spectrum Reduced Under Horizontal Earthquake
4.7 and 4.8.2 which are given in the calculation method in the horizontal direction reduced seismic loads ' s to be used for determining reduced design acceleration spectrum 's specific T with the ordinate for the natural vibration period of reduced design spectral acceleration of S R ( T ) , Eq. (4.8) It is defined by:
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Wherein S aa ( T ) , 02.02 defined in formula DD-2 earthquake motion Eq. (2.2) determined by the horizontal elastic design spectral acceleration , expand R ( T a ) is from Eq. (4.1) defined by Seismic Load Reduction Factor It shows.
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12.9.1.2 Modal Response Parameters
The value for each force-related design parameter of interest, including story drifts, support forces, and individual member forces for each mode of response, shall be computed using the properties of each mode and the response spectra defined in either Section 11.4.6 or 21.2 divided by the quantity R ∕ Ie. The value for displacement and drift quantities shall be multiplied by the quantity Cd ∕ Ie.
C12.9.1.2 Modal Response Parameters
The design response spectrum (whether the general spectrum from Section 11.4.6 or a site-specific spectrum determined in accordance with Section 21.2) is representative of linear elastic structures. Division of the spectral ordinates by the response modification coefficient, R, accounts for inelastic behavior, and multiplication of spectral ordinates by the Importance Factor, Ie, provides the additional strength needed to improve the performance of important structures. The displacements that are computed using the response spectrum that has been modified by R and Ie (for strength) must be amplified by Cd and reduced by Ie to produce the expected inelastic displacements.
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