Time History

02-Analytical capabilities
Post Reply
Ian_H
Posts: 3
Joined: 04 Jan 2014, 17:34

Time History

Post by Ian_H »

Hi,

I am trying to ascertain how to achieve my objective. I am using Robot Structural Analysis to carry out a seismic analysis of a structure using the time history method with accelerations in three axis. Am I correct in thinking I can generate a text file using Artif containing the accelerations? I need to generate an event representing a moment magnitude of 8. This can be hypothetical or can be a real earthquake of this magnitude.

I am currently thinking I can generate a spectrum in Spect and bring this into Artif to form the basis of the time history file?
huffte
Posts: 978
Joined: 22 Jul 2011, 10:19
Location: Cookeville, Tennessee, USA
Contact:

Re: Time History

Post by huffte »

Hi Ian_H.

You do have several options. Ideally, you would have a target acceleration response spectrum, which would be the design basis from the governing code (UBC, IBC, AASHTO, ASCE 7, etc . . .).

With a target response spectrum in hand, you could generate the M8 accelerograms for the appropriate site class and distance-to-source criteria specified in SeismoArtif. You could then adjust these synthetic accelerograms in SeismoArtif using the Synthetic Accelerogram Generation and Adjustment calculation method. You can generate up to 8 accelerograms at a time. Most codes require 7 for the analysis when the average response is taken as the design basis.

You can also adjust real records to the target spectrum using either SeismoArtif (Real Accelerogram Adjustment calculation method) or SeismoMatch.

The closest thing I have found to M8 earthquake accelerograms are the M7.9 Denali, Alaska event in 2002 (PEER Ground Motion Database), the M7.62 Chi-Chi Taiwan event in 1999 (PEER), the M7.9 Wenchuan event in 2008 (difficult to find records but they are scheduled to be added to PER soon), and the Mexico City M8.0 event in 1985 (COSMOS ground motion database).

Given that sparsity of M8 records, your best bet may be synthetic accelerograms with SeismoArtif, or a combination of synthetic records with Denali real records. Pay close attention to site conditions and distance-to-source metrics when selecting real records and adjust everything to the target response spectrum

And yes, you can save the adjusted accelerograms from SeismoArtif to text files which can be read by structural analysis software packages.

Best of luck Ian_H.
Tim Huff
Ian_H
Posts: 3
Joined: 04 Jan 2014, 17:34

Re: Time History

Post by Ian_H »

Hi,

Thanks for the reply. I have a look at the software and I can see now how to generate an M8 history based on the EC8 criteria. I haven't received my key to register the software yet (academic use) but upon hitting the 'save time history' option is it then straightforward to save acelloragrams with accelerations in X Y Z axis?
huffte
Posts: 978
Joined: 22 Jul 2011, 10:19
Location: Cookeville, Tennessee, USA
Contact:

Re: Time History

Post by huffte »

You will be generating 1 horizontal component at a time. With both components adjusted to the same EC8 spectrum, the geometric mean will also be approximately matched to the same EC8 spectrum, so that you could apply two of the generated components in perpendicular horizontal directions. For the vertical component, if needed, you could create a synthetic record adjusted to 2/3 of the horizontal spectrum.

You may easily save time histories of acceleration, velocity, or displacement as text files once the adjusted records have been created using the Save Time Histories command. You will be prompted for a prefix which will subsequently be used in the filenames.
Tim Huff
Ian_H
Posts: 3
Joined: 04 Jan 2014, 17:34

Re: Time History

Post by Ian_H »

Thank you for the help and advice - it is much appreciated.
Post Reply

Return to “02-Analytical capabilities”