Ground Motion Data Conversion

[huffte]

It appears that the data are harmonic loadings of varying frequency. Since the amplitudes are in mm, you would need to create acceleration histories by first calculating Asin(wt), where A is the amplitude and w is the frequency in radians per second (obtained by multiplying the given frequency in Hz by 2pi). You could assign a delta t of 0.005 seconds, for example, and use Excel to do all the calculations. You would then have to numerically differentiate (also within Excel) the displacement history twice to obtain the acceleration history, which could be loaded into SeismoSignal. So, SeismoSignal may not be what you need. You could do all of this in Excel to get the acceleration histories. Or else, you could search for software which can generate harmonic time histories from amplitude, duration, and frequency data.

[huffte]

The acceleration history needs to be time versus acceleration. So, for a 25 second duration at each given frequency, you could start at time 0.000, at each step of 0.005 seconds, do the required computations, and keep stepping by 0.005 seconds until you reach 25 seconds. Then move on to the next frequency and continue the calculations. You will have 5,000 (time, acceleration) values (25/0.005 = 5,000) at each frequency.

time acceleration
0.000 0.000
0.005 0.036
0.010 0.042
0.015 0.067
0.020 -0.012
. . .
. . .
25.000 0.000

[huffte]

The numbers in my second post are just made-up examples of what the file should look like. For actual values, from my previous post, I quote:

'create acceleration histories by first calculating Asin(wt), where A is the amplitude and w is the frequency in radians per second (obtained by multiplying the given frequency in Hz by 2pi)'