A “Single Point Response Spectrum” (SPRS) Analysis in Ansys
Sector: Machinery and plant engineeringSpecialist field: Structural mechanicsCPI VERTEX Antennentechnik GmbH is the manufacturer of the ALMA (Atacama Large Millimeter Array) telescope with an antenna diameter of 12m. For this system, an earthquake analysis based on a response spectrum (SPRS) is required, which CADFEM prepared with Ansys simulation tools.
Summary
Task
For large buildings or other tall structures, especially at locations in seismically active regions, an earthquake analysis is often required. An FE analysis is therefore performed to verify the integrity of the structure during an earthquake.
Solution
CADFEM first performed a modal analysis in Ansys to obtain the natural frequencies and mode shapes of the structure. After that, the mode shapes were scaled according to the given response spectrum.
Customer benefits
With the response spectrum analysis, the customer does not receive the calculations from the entire course of an earthquake. Rather, the analysis is a simplified method for determining what happens at the expected maximum value.
Project Details
Task
For large buildings or other tall structures, especially at locations in seismically active regions, an earthquake analysis is often required. An FE analysis is therefore performed to verify the integrity of the structure during an earthquake. In this case, the 12m ALMA (Atacama Large Millimeter Array) telescope was analyzed.
Customer Benefit
This type of response spectrum analysis does not calculate the entire course of the earthquake. Rather, it is a simplified method for determining what happens at the expected maximum value. This approach even allows the analysis of large models with more than a few million degrees of freedom. A special filter technique is used to suppress negligible modes. Usually, a certain percentage of the total structural mass must participate in the oscillation. For this purpose, modal participation factors and modal effective masses from Ansys can be applied.
Solution
A response spectrum for the given earthquake location is defined, for example, by the authorities (see figure). The task of the analyst is now to first perform a modal analysis to obtain the natural frequencies and mode shapes of the structure. After that, the mode shapes are scaled according to the given response spectrum. A mode combination method such as SRSS or CQC is applied to obtain the final result, e.g., in the form of the maximum displacement (see figure SRSS model).
Images: © CPI VERTEX Antennentechnik GmbH