WAVGEN

Wavelet-Based Generation of Spectrum-Compatible Ground Motion

 

 

 

WAVGEN modifies a given (recorded) accelerogram to make it compatible with a given Pseudo Spectral Acceleration (PSA) spectrum.

 

This code follows the wavelet-based algorithm proposed by (a) S. Mukherjee and V.K. Gupta (2002): Wavelet-Based Generation of Spectrum-Compatible Time-Histories, Soil Dynamics and Earthquake Engineering, Vol. 22, No. 9, pp. 799-804 or (b) S. Mukhopadhyay, S. Das and V.K. Gupta (2019): Wavelet-Based Generation of Accelerogram-Consistent, Spectrum-Compatible Motions: New Algorithms and Short-Period Overestimation, Soil Dynamics and Earthquake Engineering, Vol. 121, pp. 327-340.

 

There are three versions of WAVGEN:

(a) the original version, WAVGEN_1, based on Mukherjee and Gupta (2002),

(b) the modified version, WAVGEN_2, based on Mukhopadhyay et al. (2019), and

(c) an alternative version of WAVGEN_2 using FFT-based decomposition of the seed accelerogram.

 

 

Files to be Downloaded for WAVGEN_1 and WAVGEN_2:

 

WavGen.exe for WAVGEN_1

 

WavGen2_WT.exe (to be run) and auxiliary.exe for WAVGEN_2

 

WavGen2_FFT.exe (to be run) and auxiliary_fft.exe for alternative WAVGEN_2

 

For all three versions, users should also download the file, T-P.dat, for the 97 time-period values at which the target PSA spectrum is to be specified.

 

The downloaded files should be kept in the same directory where the input data, i.e., accelerogram data (that is to be modified) and the target response spectrum are kept.

 

The user may need to install the MatLab runtime for WAVGEN_2 from https://ssd.mathworks.com/supportfiles/downloads/R2024b/Release/4/deployment_files/installer/complete/win64/MATLAB_Runtime_R2024b_Update_4_win64.zip

(when the same version of MatLab is not installed as that used for generating the executable file or when MatLab is not at all installed).

 

Input Data:

 

Two data files are required by WAVGEN_1 and WAVGEN_2 as the input data:

 

1. accelerogram.dat (this corresponds to the seed accelerogram that is to be modified)

First line in this file contains the (uniform) time-step of the accelerogram data.

Subsequent n lines contain the n values of recorded acceleration (in g).

 

2. target.dat (this corresponds to the target PSA spectrum)

This file contains the PSA data in two columns (from Lines 1 to 97).

First column contains the 97 time-period values as in T-P.dat.

Second column contains the 97 values of PSA (in g).

The target spectrum must be specified at all 97 time-period values (without altering any of the period values, taking less/more than 97 values, or leaving any blanks in the second column).

 

3. In the case of WAVGEN_1, when the program runs, it prompts the user to specify the damping to which the target spectrum corresponds. One should type 0.05 if the target spectrum corresponds to 5% viscous damping of critical. In the case of WAVGEN_2, this information is provided through an additional data file, damping.dat.

 

 

Output Data:

 

The output of WAVGEN is stored in compatible.dat in the directory where the user is working. The modified accelerogram data is stored in the same format as the input file accelerogram.dat (i.e., time-step value in the first line is followed by the n values of modified acceleration (in g) in the subsequent n lines). The output data may need to be base-line corrected.

 

 

Sample Files:

 

accelerogram.dat (accelerogram before modification)

target.dat (target PSA spectrum)

compatible.dat (accelerogram after modification) in the case of WAVGEN_1

compatible2_WT.dat or compatible2_FFT.dat (accelerogram after modification) in the case of WAVGEN_2

damping.dat (damping ratio of target PSA spectrum)

 

 

Questions/Comments/Suggestions:

 

Please write to: Dr. Vinay K. Gupta at vinaykg@iitk.ac.in.