*RESPONSE SPECTRUM

Calculate the response based on user-supplied response spectra.

This option is used to calculate estimates of peak values of nodal and element responses based on user-supplied response spectra (defined using the SPECTRUM option) and on the natural modes of the system.

This page discusses:

See Also
*SPECTRUM
In Other Guides
Response Spectrum Analysis

ProductsAbaqus/Standard

TypeHistory data

LevelStep

Optional parameters

COMP

Set COMP=ALGEBRAIC to sum the directional excitation components algebraically. If this parameter is used, the directional excitation components are summed first, followed by the modal summation.

Set COMP=SRSS (default) to use the square root of the sum of the squares. If this parameter is used, the modal summation is performed first, followed by the summation of the directional excitation components.

Set COMP=R40 to use the 40% rule as recommended by the ASCE 4–98 Guide that assumes that for the maximum response from one component, the responses from the other two components are 40% of their maximum value.

Set COMP=R30 to use the 30% rule. This rule assumes that for the maximum response from one component, the responses from the other two components are 30% of their maximum value. It follows the expressions for the 40% rule as described in the ASCE 4–98 Guide.

MISSING MASS METHOD

Include this parameter to achieve greater response accuracy by augmenting the missing inertia in the dynamic response. Quasistatic residual modes in the direction of applied spectra are substituted for the truncated higher frequency modes that belong to the in-phase (rigid) response.

RIGID RESPONSE

Set RIGID RESPONSE=GUPTA to use the Gupta method for modal summation of periodic and rigid regions in the response spectrum. If this parameter is omitted, no rigid response is included.

Set RIGID RESPONSE=LINDLEY-YOW to use the Lindley-Yow method for modal summation of periodic and rigid regions in the response spectrum. If this parameter is omitted, no rigid response is included.

SUM

Set SUM=ABS (default) to sum the absolute values of the responses in each natural mode.

Set SUM=CQC to use the complete quadratic combination method to sum the responses in each natural mode.

Set SUM=DSC to use the double sum combination. This method is the first attempt to evaluate modal correlation based on random vibration theory. It utilizes the time duration tD of strong earthquake motion.

Set SUM=GRP to use the grouping method as described in USNRC Regulatory Guide 1.92, February 1976.

Set SUM=NRL to use the Naval Research Laboratory method.

Set SUM=SRSS to use the square root of the sum of squares summation.

Set SUM=TENP to use the Ten Percent Method.

Data lines for a response spectrum analysis

First line

  1. Name of the response spectrum to be used.

  2. X-direction cosine of this direction.

  3. Y-direction cosine of this direction.

  4. Z-direction cosine of this direction.

  5. Factor multiplying the magnitudes in the response spectrum. Default is 1.0.

  6. Time duration of the dynamic event, from which this spectrum was created. This value is required for the DSC modal summation rule.

  7. Frequency of the zero period acceleration or cut-off-frequency value in cycles per time. Default is 33 Hz. This value is used for the Lindley-Yow rigid response method. If the Gupta rigid response method is used, this is the F1 frequency value in cycles/time.

  8. For the Gupta rigid response method, enter the F2 frequency value in cycles/time.

Second line (optional)

  1. Name of the response spectrum to be used in the second direction.

  2. X-direction cosine of this direction. This direction must be at a right angle to the direction defined above.

  3. Y-direction cosine of this direction. This direction must be at a right angle to the direction defined above.

  4. Z-direction cosine of this direction. This direction must be at a right angle to the direction defined above.

  5. Factor multiplying the magnitudes in the response spectrum. Default is 1.0.

  6. Time duration of the dynamic event, from which this spectrum was created. This value is required for the DSC modal summation rule.

  7. Frequency of the zero period acceleration or cut-off-frequency value in cycles per time. Default is 33 Hz. This value is used for the Lindley-Yow rigid response method. If the Gupta rigid response method is used, this is the F1 frequency value in cycles/time.

  8. For the Gupta rigid response method, enter the F2 frequency value in cycles/time.

Third line (optional)

  1. Name of the response spectrum to be used in the third direction.

  2. X-direction cosine of this direction. This direction must be at right angles to the two directions defined above.

  3. Y-direction cosine of this direction. This direction must be at right angles to the two directions defined above.

  4. Z-direction cosine of this direction. This direction must be at right angles to the two directions defined above.

  5. Factor multiplying the magnitudes in the response spectrum. Default is 1.0.

  6. Time duration of the dynamic event from which this spectrum was created. This value is required for the DSC modal summation rule.

  7. Frequency of the zero period acceleration or cut-off-frequency value in cycles per time. Default is 33 Hz. This value is used for the Lindley-Yow rigid response method. If the Gupta rigid response method is used, this is the F1 frequency value in cycles/time.

  8. For the Gupta rigid response method, enter the F2 frequency value in cycles/time.