Accelerograms Scale factor

03-Analytical/modelling capabilities
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Mostafa Ghanem
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Joined: 14 Dec 2017, 16:58

Accelerograms Scale factor

Post by Mostafa Ghanem » 20 Jan 2018, 15:26

Dears at Seismosoft,

When i create a model in building modeler and choose type of analysis : Dynamic History Analysis and when i press exit and create project i am asked to load an accelerogram file which i have to define the scale factor but afterwards when i go to applied load i found another scale factor (9.81) which is the default of the program.So my question is should i change the scale factor at the applied load menu also or just change the scale factor once at loading the accelerogram file ?

huffte
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Joined: 22 Jul 2011, 10:19
Location: Cookeville, Tennessee, USA
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Re: Accelerograms Scale factor

Post by huffte » 20 Jan 2018, 16:10

Hi Mostafa. There are many different ways to get the same correct answer to this question. I will offer up my method of applying scale factors to accelerograms in SeismoSoft programs as it seems logical to me.

The scale factor applied when the accelerograms is loaded is the amplification factor needed to scale the accelerograms up to the desired design level. Often in seismic design, we select records from various recorded events and scale them so that each of the individual elastic response spectra closely matches a target response spectrum.

The scale factor applied when the loading is defined is used to convert the units from g to length units per second squared.

So, if you are using unscaled (as recorded) accelerograms and do not wish to amplify them, use 1.0 for the first scale factor and 9.81 for the second scale factor (if your current units are meters).

Note that you could get the exact same result by switching the scale factors. But it makes more sense (to me at least) to use the factors as outlined above. I hope this helps. Best of luck, Mostafa.
Tim Huff

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