Generating Response Spectrum With resp Command
Attached input file and sample acceleration over time file generate response spectrum from measured acceleration over time data. Base assumption is that mesurement data is stored in a comma separated file, time in first column and acceleration in second column. Decimal separator has to be period.
Input file is run in batch from Mechanical APDL launcher or from command line. Input file assumes measurement data file is in working directory set for batch run.
Measurement data filename is set on lines 45 and 62 on attached input file.
To be able to use external data for resp command we need to do a bit of trickery, in the form of solving a static analysis on a single beam element to get a result file that has the same number of result points as the measurement data has. That is required because /post26 uses the loaded result file to determine vector length for resp command. Length of measurement data in lines is checked from the file with /inquire command.
Solution runs, then in /post26 the file is read in and two vput commands insert time and acceleration values from measurement data to /post26 variables. Then filldata command is used to add a variable that has desired frequencies for the response spectrum. Finally resp command generates response spectrum and the result is written to a file with /output and prvar command. Response spectrum values can then be copied from resp.txt file to loads in final analysis.