Nonlinear dynamic analysis

[shchao99]

Hi,

When running a nonlinear dynamic analysis for a building, we must use a real earthquake acceleration time history. I was wondering should I scale the PGA of the real EQK to the design PGA I got from the UBC design spectrum?

Thanks

 

[alashki]

Hi,
If you running nonlinear calculations with nonlinear materials behavior you must use real earthquake acceleration without any reduction.

But, If you running nonlinear or linear calculations with elastic (constant) material behavior you must scale the real earthquake acceleration with behavior factor according to seismic design code.

The reason for reducing the real response spectrum to design response spectrum is the nonlinear materaial behavior when the structure is subjected to a seismic excitation.

Regards,

Dr. Ilia Alashki

CV:

http://www.alashki.com/cv.htm

Projects:

http://www.alashki.com/projects.htm

Ilia Alashki
e-mail: ilia@alashki.com

http://www.alashki.com

 

[shchao99]

Hi, Dr. Alashki--
Thanks for the clear reply. I understand now.

There is another question about the nonlinear dynamic analyis. If I perform a nonlinear dynamic analysis for a building structure by using several different EQK time-histories, should I scale each of the PGA to some value so that I can compare their effects on the structure? Or, I can use directly all of them?

Thanks a lot!

 

[alashki]

If you would like to investigate the real affect of EQ excitation to building structure (for example, when you have to give an expert opinion about an erected structure)you have to use time-history records without any scaling for calculation with nonlinear material behavior and scaled by behavior factor for calculations with constant material properties.

But If you need to estimate the design forces in the elements (during project stage)it is also possible to scale max values of time-history records to max value of design response spectra. (This implicitly means that you are using linear dynamic calculation). In this case you are able to compare the structure response from different EQA time-history records and Response Spectrum Method.

Ragards,


Dr.Ilia Alashki
e-mail: ilia@alashki.com
WEB Site:

http://www.alashki.com

CV:

http://www.alashki.com/cv.htm

Projects:

http://www.alashki.com/projects.htm