seismic sequences

03-Analytical/modelling capabilities
newman
Posts: 38
Joined: 06 Jan 2017, 18:12

seismic sequences

Post by newman » 31 Jan 2019, 17:43

Dear Seismosoft,
I have three earthquake (defined with three different curves in seismostruct) with three different dt. I want to analyze a frame under these earthquakes as a seismic sequences. How can I do that? Is it possible in Seismostruct without any further works on seismograms?
Is the following method true?:
1_ apply all three earthquakes to the base nodes
2_ define the first earthquake with a curve starts from 0 to 40, without delay.
3_ define the second earthquake with a curve starts from 0 to 55, with delay equal to 40 sec.
4_ define the third earthquake with a curve starts fron 0 to 35, with a delay equal to 40+55=95 sec.
Also, in defining each curve, the amounts of dt should be consider based on dt1, dt2, dt3? Three stages? Is it true?

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seismosoft
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Joined: 06 Jul 2007, 04:55

Re: seismic sequences

Post by seismosoft » 01 Feb 2019, 09:45

In SeismoStruct it is not possible to apply a 'delay' to the records. However, it is possible to define the records with the 'correct' time at the different stages (e.g. your second record could have a time between 40 and 55 sec).
Further, in the same module it is possible to define multiple stages, so that to adapt the time-step dt according to the intended accuracy and the convergence difficulties of the analysis
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newman
Posts: 38
Joined: 06 Jan 2017, 18:12

Re: seismic sequences

Post by newman » 01 Feb 2019, 19:30

Thank you for the response. As I understood, I have to change the time of the second record so that its starting point should equal to 40 sec. Did I get it right?

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z.gronti
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Joined: 16 Oct 2013, 08:14

Re: seismic sequences

Post by z.gronti » 05 Feb 2019, 11:07

Dear newman,

When you load a new curve, there is the "Delay" option available in the "Input File Parameters" where you can define the time at which a particular time-history starts being applied to the structure.
Zoi Gronti
Seismosoft Srl.

prestige
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Joined: 21 Jan 2019, 12:01

Re: seismic sequences

Post by prestige » 19 Feb 2019, 16:26

Hi , i have a question
If the earthquake time about 100s ,can we applied peak time(about 20s) ,for running IDA analysis?
(To take maximum inter story drift)

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seismosoft
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Re: seismic sequences

Post by seismosoft » 20 Feb 2019, 12:31

Not sure what you mean Prestige. If you have a record of 100 sec, you can only run the first 20 sec by defining correctly the time-history stages.
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prestige
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Joined: 21 Jan 2019, 12:01

Re: seismic sequences

Post by prestige » 27 Feb 2019, 15:58

tanks for answer my question
your idea is true.

prestige
Posts: 8
Joined: 21 Jan 2019, 12:01

Re: seismic sequences

Post by prestige » 02 Mar 2019, 17:09

hi
i have a question
i want to do IDA analysis to obtain maximum response(such as peak drift,..) and the applied earthquake is San Fernando with 79.44 sec time duration, if i use the stage step time until 22 sec (peak of earthquake occur in 7 sec).
the seismic sequences is it true?

huffte
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Location: Cookeville, Tennessee, USA
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Re: seismic sequences

Post by huffte » 03 Mar 2019, 14:49

I don't believe you can rely on the results, prestige. Just because the peak ground acceleration occurs at 7 seconds, doesn't necessarily mean that the maximum structural response has been achieved by 22 seconds. There could be lower amplitude ground motion with frequency content significant to structural response beyond 22 seconds of the record. Could you capture the maximum response by running only 22 seconds? Possibly. But you cannot be certain of it. The safe choice is to run the entire record.
Tim Huff

prestige
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Joined: 21 Jan 2019, 12:01

Re: seismic sequences

Post by prestige » 05 Mar 2019, 16:16

tank Tim Huff
Perhaps your point is correct, but the view of other researchers is that the maximum response takes place at the most effective time, which is the maximum acceleration.
in IDA analysis ,If I want to apply the whole time of the earthquake, it can not be more than seven points scale factor because the output volume exceeds 2GB.
In order to apply more scale factor points, the duration of the earthquake should be considered less.
what is your opinion?

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