Displacements, Velocities and Accelerations Converter


Program objectives

This program allows the conversion between time records of displacements, velocities and accelerations, as it is described by Bath (1974). Thus, you can get time records of accelerations or velocities from seismic records, accelerations or seismic records from time records of velocities and velocities or seismic records from time records of accelerations, as it will be described below (Corchete, 2010).

Program description

The AVD program and its files, which are needed to run this application, are enclosed into a ZIP file named "AVD.zip". When you have got the ZIP file and you have uncompressed this file, you have four files named AVD.exe, series.dat, S408.dat and spectrum.dat. The file AVD.exe contains a program (in FORTRAN code for PC) for the computation of the conversion between time records of displacements, velocities and accelerations.

Running the program

Firstly, we need obtain the input file to be converted with the AVD program. For it, the SERIES program can be very useful. This program can be run with the input files: series.dat and S408.dat, which are enclosed in the ZIP file named AVD.zip. After that, the file displacement.dat is generated and, then, we can run the AVD program using this file as input-data file. When we run the AVD program the following menu is displayed:

Conversion menu:
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1. Computation of accelerations and velocities from displacements.
2. Computation of accelerations and displacements from velocities.
3. Computation of velocities and displacements from accelerations.

... select the option (1,2,3):

Then, we can do each action shown in this menu entering the corresponding number. If we select OPTION = 1, the program will compute the accelerations and velocities from a time record of displacements. In this case, an ASCII file with the Fourier spectrum of a time record of displacements, must be supplied. In this example, this input-data file is supplied by the SERIES program, it is the file displacement.dat. Figure 1, shows the amplitude spectrum contained in this file. After the computation, two new files have been generated velocity.dat and acceleration.dat (also shown in Figure 1).

Fig. 1. Amplitude spectrum for the displacements, velocities and accelerations, contained in the files displacement.dat, velocity.dat and acceleration.dat, respectively.

If we want to get the time records corresponding to these Fourier spectra, we can use the SPECTRUM program with the option 0. After the computation, three new files have been generated sd.dat, sv.dat and sa.dat. These time records are shown in Figure 2. Obviously, we can choose other options of the AVD program to get accelerations and displacements from velocities or velocities and displacements from accelerations. The computation process is in the same way, we need to get previously the Fourier spectrum of the input time record, and after we can run the programs AVD (to get the Fourier spectra) and SPECTRUM (to get the time records) to get the converted time records. In all cases, the origin time of the input time record is lost, because the Fourier spectrum has not information about it. For this reason, this origin time must be added to the time scale of the output time records.

Fig. 2. Time records for the displacements, velocities and accelerations, contained in the files sd.dat, sv.dat and sa.dat, respectively.

References

Bath M., 1974. Spectral analysis in Geophysics. Elsevier, Amsterdam.

Corchete V., 2010. The analysis of accelerograms for the earthquake resistant design of structures. International Journal of Geosciences, 2010, 32-37.