bracketed and effective duration

02-Analytical capabilities
anjaliuday1
Posts: 5
Joined: 08 May 2015, 12:57

bracketed and effective duration

Post by anjaliuday1 »

How to determine bracketed and effective duration using seismosignal? For bracketed duration, a threshold value of 0.05g is to be used. What are the absolute values to be used as thresholds for determining effective duration as per Bommer and Pereira? What is the default value used for effective duration in seismosignal?
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ruipinho
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Joined: 07 Dec 2013, 14:37

Re: bracketed and effective duration

Post by ruipinho »

Dear anjaliuday1,

I am not sure I understand your query, since all you need to do is to run the program, go to the 'Ground Motion Parameters' module, select the 'Durations' tab, and calculate the parameters you mention. So, what specific difficulties are you experiencing?

Rui
anjaliuday1
Posts: 5
Joined: 08 May 2015, 12:57

Re: bracketed and effective duration

Post by anjaliuday1 »

Sir,
I want to determine effective duration for different strong ground motions. When I input some of the acceleration time histories, the software is showing the limits of effective duration by default. But for some other motions, default values are in red. So I wanted to know what criteria the software is following for giving default values of threshold for effective duration?
huffte
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Location: Cookeville, Tennessee, USA
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Re: bracketed and effective duration

Post by huffte »

At least on my system, it appears that the default limits for effective duration thresholds are 5% and 95% of the Arias intensity value listed in the parameters, rounded to 2 decimal places. The rounding gives slightly different answers when the defaults are used for effective duration compared to what I get for significant duration at 5%/95% thresholds. I have tried, but have not yet been able to reproduce the red-valued (supposedly invalid) default thresholds for effective duration.
Tim Huff
anjaliuday1
Posts: 5
Joined: 08 May 2015, 12:57

Re: bracketed and effective duration

Post by anjaliuday1 »

Sir,
What is the range of PGA of the data you have used? Is the minimum value of Arias intensity 0.135m/s ?
huffte
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Location: Cookeville, Tennessee, USA
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Re: bracketed and effective duration

Post by huffte »

I have processed dozens of accelerograms of various PGA. The bounds of Arias intensity change every time I load a new accelerogram.
Tim Huff
anjaliuday1
Posts: 5
Joined: 08 May 2015, 12:57

Re: bracketed and effective duration

Post by anjaliuday1 »

Sir,
Regarding bracketed duration I am using a threshold value of 0.05g. So the input acceleration level should be given as 0.05 or its square 0.0025? (the doubt is due to the graph which is plotted as the square of acceleration vs time)
Can you suggest any reason as to why I am getting default values in red for some cases of effective duration?
huffte
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Joined: 22 Jul 2011, 10:19
Location: Cookeville, Tennessee, USA
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Re: bracketed and effective duration

Post by huffte »

The appropriate value to enter for bracketed duration in your example would be the actual acceleration, 0.05. Note that the plot of the square is simply to get everything into a positive value. And also note that for an input value of, say 0.30, the plotted value is 0.09 as expected.

Regarding red values for specified parameters, the only way I have been able to reproduce such a red valued parameter is by specifying a threshold greater than the maximum acceleration for bracketed duration, entering a zero value, or entering a value greater than the maximum Arias intensity for effective duration.
Tim Huff
anjaliuday1
Posts: 5
Joined: 08 May 2015, 12:57

Re: bracketed and effective duration

Post by anjaliuday1 »

Sir,
I am using data with PGA from 0.01g -0.3g recorded at distances up to 520km. For effective duration, I am not able to give input threshold values as mentioned in Bommer and Pereira (1999) i.e. 0.01m/s and 0.125m/s of Arias intensity.
So, if the software is using the same threshold values as significant duration (5-95%), then what is the difference between the two? Moreover absolute criteria needs to be used for effective duration too. Please give your valuable suggestion.
huffte
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Joined: 22 Jul 2011, 10:19
Location: Cookeville, Tennessee, USA
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Re: bracketed and effective duration

Post by huffte »

I am still puzzled that you cannot enter desired threshold values for effective duration. Again, the only way I can reproduce that is to enter a 0 for the lower threshold or a value greater than the total Arias intensity for the upper threshold. Nonetheless, I get the same answer for effective and significant durations when I enter thresholds of 0.05,0.95 (significant duration) and 0.0852, 1.619 (effective duration). The total Arias intensity for the record I chose this morning is 1.704, hence, the two values for effective duration.
Tim Huff
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