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Section 5
5-293
5.32.10.1 Response Spectrum Specification
Purpose
This command may be used to specify and apply the RESPONSE
SPECTRUM loading for dynamic analysis.
General Format:
⎧SRSS ⎫ * ⎧X f1 ⎫ ⎧ACC ⎫
SPE
CTRUM ⎨ABS ⎬ ⎨Y f2 ⎬ ⎨ ⎬ (SCALE f4)
⎪CQC ⎪ ⎩Z f3 ⎭ ⎩ DIS ⎭
⎪ASCE ⎪
⎩TEN ⎭
⎧ DAMP f5 ⎫ ⎧LIN ⎫
⎨ CDAMP ⎬ ( ⎨ ⎬ ) (MIS f6) (ZPA f7) (FF1 f8) (FF2 f9) (SAVE)
⎩ MDAMP ⎭ ⎩LOG ⎭
The data in the first line above must be on the first line of the command, the remaining data can
be on the first or subsequent lines with all but last ending with a hyphen (limit of 3 lines ).
Starting on the next line, enter Spectra in one of these two input forms:
⎧ P1 V1; P2 V2; P3 V3;…… ⎫ (with DAMP, CDAMP, or MDAMP)
⎨ or ⎬
⎩ FILE fn ⎭ (with CDAMP or MDAMP)
SRSS , ABS , CQC, ASCE4-98 & TEN Percent are methods of
combining the responses from each mode into a total response.
The CQC&ASCE4 methods require damping, ABS, SRSS,
and TEN do not use damping unless Spectra-Period curves are
made a function of damping (see File option below). CQC,
ASCE and TEN include the effect of response magnification
due to closely spaced modal frequencies. ASCE includes more
algebraic summation of higher modes. ASCE & CQC are more
sophisticated and realistic methods and are recommended.
X Y Z f1, f2, f3 are the factors for the input spectrum to be
applied in X, Y, & Z directions. Any one or all directions can
be input. Directions not provided will default to zero.