Ground Motion Data Conversion

02-Analytical capabilities
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mfarhan12
Posts: 3
Joined: 27 Dec 2019, 09:58

Ground Motion Data Conversion

Post by mfarhan12 »

How i can convert this attached in link below frequency domain data into time history using seismoSignal ?
Actually this is the data used for Shake Table testing. I have to use this data in Time History (Time vs Acceleration) form for my numerical simulation purpose.
Can anybody help me please ?

http://www.mediafire.com/file/sb3c1jdhy ... signal.PNG

huffte
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Location: Cookeville, Tennessee, USA
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Re: Ground Motion Data Conversion

Post by 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.
Tim Huff

mfarhan12
Posts: 3
Joined: 27 Dec 2019, 09:58

Re: Ground Motion Data Conversion

Post by mfarhan12 »

Thanks.
Can i use the given time of 25 seconds given in table for "t" as you have mentioned in your reply for calculation instead of 0.005 sec. And what is delta t ?. As you have mentioned only "t" in the equation.

huffte
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Location: Cookeville, Tennessee, USA
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Re: Ground Motion Data Conversion

Post by 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
Tim Huff

mfarhan12
Posts: 3
Joined: 27 Dec 2019, 09:58

Re: Ground Motion Data Conversion

Post by mfarhan12 »

Thanks, Tim Huff for your quick reply.
Could you please elaborate, how have got the second column of acceleration ?
Procedure ?

huffte
Posts: 856
Joined: 22 Jul 2011, 10:19
Location: Cookeville, Tennessee, USA
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Re: Ground Motion Data Conversion

Post by 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)'
Tim Huff

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