Chopra Example for El Centro 2

[JoshPlumSE]

This will seem like an odd question. But, I'm trying to find a time history record used in Chopra's Dynamics of structures. Does anyone know where to find this. The book claims that it is the NS component of the El Centro earthquake measured at the Imperial Valley Irrigation district. However, it gives a max acceleration of 0.319g.

And, all the El Centro NS records that I have seen have a maximum acceleration of 0.349g. It seems like Chopra's might be measured from a different station. But, I can't find it.

I can't be the only one who has tried to validate a program's time history feature by comparing his model results against the results in Chopra's example. So, what am I missing?

 

[SlideRuleEra]

Josh - Is this the record that you are looking for? Looks like the maximum value is about 0.32g, at 2 seconds after the initial shock.

See the note: "The instrument that recorded the accelerogram was attached to the El Centro Terminal Substation Building’s concrete floor, and not in a free-field location. The record may have under-represented the high frequency motions of the ground because of soil-structure interaction of the massive foundation with the surrounding soft soil."

Here is the link:

http://www.vibrationdata.com/elcentro.htm

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[JoshPlumSE]

That's the one I already have. Maximum acceleration = 0.349 at 2.12 seconds. But, Chopra's shows a maximum of 0.319g.

2.1200000e+000 3.4873739e-001

The frustrating thing is that the two time histories are pretty close, but not quite the same. So, it took me awhile to recognize that the issue was a slightly different input motion.... My values are reasonably close and the basic shape of the response is similar. Therefore, that I kept assuming I had made a mistake somewhere. But, at this point, I'm pretty sure there is a difference in the ground motion.

 

[SlideRuleEra]

The difference may be which set of data the author used. It is suspicious that the north south time-history data shows 0.319g.

(2.020000 -0.318820)
This is from the easily overlooked link just below the second graph on the web page and shows the north-south time-history data:

http://www.vibrationdata.com/elcentro.dat

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[JoshPlumSE]

Thank you!! I think that's it!

One of them is for a "free field" at the Irrigation district (which is what I was using). The other sees to correspond to an accelogram nearby that was tied to a concrete floor.

I was looking through PEER data and all over the place trying to find out if there were other / conflicting El Centro responses and I just wasn't finding anything.

Thank you again!

 

[mrsutton]

Back in structural dynamics we did a team project doing time history from El Centro for a 10-story steel building in ETABS. I think the El Centro record could be uploaded into it from some other site. It's been too long to remember now--but I'm sure if you Googled "El Centro time history record for dynamic analysis" you'd eventually find it.