Hi
i'd like to extract maximum inter-story drift ratio Based on Fema350 in order to specify a certain limit state at the recommended max drift ratio(eg:2%)
firstly the code says drift ratio:does it mean i have to divide the seismo relative displacement by story height.
secondly after i have realized the corresponding "first mode spectral acceleration" to the "max drift ratio(2%)" would that be my acceleration limit state?
thirdly ,all these process would take a long time(7 records,each record 8-9 scale factors,each scale factor 4 to 8 story relative displacement)any suggestion?
Is the process right in order to detect the correct IM for a certain limit state?
the paper says "first mode spectral acceleration",is it equal to my scale factors if i had scaled my records to my deign spectra?
forgive me if some of the questions might not be related to Seismo,
Also when i check my Accelerations ,i seem to have very large values at certain nodes ,for example at Scale Factor 0.25,max acc at n111=.55 m/s^2 and n112=320 m/s^2 !!!!
BR
Behnam
IDA Result
Re: IDA Result
Drift ratio is relative displacement divided by story height.
Create a separate file for each of the 7 records with everything except the loading identical. Use SeismoBatch to run them all overnight.
The first mode SA is the SA from the design spectrum at the first mode period.
Create a separate file for each of the 7 records with everything except the loading identical. Use SeismoBatch to run them all overnight.
The first mode SA is the SA from the design spectrum at the first mode period.
Tim Huff
Re: IDA Result
Dear Tim
Thanks.
the paper says "first mode spectral acceleration",is it equal to my scale factors if i had scaled my records to my deign spectra?
Also if the vertical axis is "Intensity Measure" & the horizontal axis "Damage measure" in my case "Sa" and "max interstory drift ratio",how would i extract "Sa" from Seismo?
Also when i check my Accelerations ,i seem to have very large values at certain nodes ,for example at Scale Factor 0.25,max acc at n111=.55 m/s^2 and n112=320 m/s^2 !!!!
Thanks.
the paper says "first mode spectral acceleration",is it equal to my scale factors if i had scaled my records to my deign spectra?
Also if the vertical axis is "Intensity Measure" & the horizontal axis "Damage measure" in my case "Sa" and "max interstory drift ratio",how would i extract "Sa" from Seismo?
Also when i check my Accelerations ,i seem to have very large values at certain nodes ,for example at Scale Factor 0.25,max acc at n111=.55 m/s^2 and n112=320 m/s^2 !!!!
Re: IDA Result
The first mode spectral acceleration is, as I say above, the spectral acceleration at the first mode of the structure. It is NOT the scale factor. You need to do an eigenvalue analysis of your structure and determine the fundamental natural period. Then read the spectral acceleration at that period from your design, EC8 spectrum.
If you look at your model, you will note that node 111 is a support node, so it sees the ground acceleration. Node 112 is not a support node. However, you may wish to double-check your units. Your reported acceleration for n111 appears to be in g, whereas your reported acceleration for n112 appears to be cm/s^2.
If you look at your model, you will note that node 111 is a support node, so it sees the ground acceleration. Node 112 is not a support node. However, you may wish to double-check your units. Your reported acceleration for n111 appears to be in g, whereas your reported acceleration for n112 appears to be cm/s^2.
Tim Huff
Re: IDA Result
Dear
1.the first mode spectral acceleration as you said would give a single value but it is supposed to be the vertical axis.(several accelerations)attached pls find the .png
2.regarding the accelerations they seem to be ok for the chevron braced frame but in the knee-brace unusual values.(attached pls find the pics)
Kind Regards
Behnam
http://www.fileconvoy.com/dfl.php?id=gd ... 8b9f3dc74d
1.the first mode spectral acceleration as you said would give a single value but it is supposed to be the vertical axis.(several accelerations)attached pls find the .png
2.regarding the accelerations they seem to be ok for the chevron braced frame but in the knee-brace unusual values.(attached pls find the pics)
Kind Regards
Behnam
http://www.fileconvoy.com/dfl.php?id=gd ... 8b9f3dc74d
Re: IDA Result
In IDA, the first mode spectral acceleration does change since the design spectrum is scaled for each subsequent analysis.
Tim Huff
Re: IDA Result
Dear Tim
i appreciate your help.
somewhere you kindly said"Sadraddin, your specified scaling factors will correspond to the various values of the first mode spectral acceleration"
my major question is :if i wish to define failure based on Drift Limit State ,how can i find the corresponding acceleration ?
the X-axis can easily be obtained(MAX IDR),but how can i find the corresponding acceleration(Y-axis)?
http://tinypic.com/view.php?pic=mab69e&s=9
I hope i made my point clear.
BR
Behnam
i appreciate your help.
somewhere you kindly said"Sadraddin, your specified scaling factors will correspond to the various values of the first mode spectral acceleration"
my major question is :if i wish to define failure based on Drift Limit State ,how can i find the corresponding acceleration ?
the X-axis can easily be obtained(MAX IDR),but how can i find the corresponding acceleration(Y-axis)?
http://tinypic.com/view.php?pic=mab69e&s=9
I hope i made my point clear.
BR
Behnam
Re: IDA Result
It depends on each particular case and what the analyst is accomplishing, Behnam. There is a one-to-one correspondence between the scale factor and the first mode spectral acceleration, but they are not necessarily equal. Take an example. Suppose your structure has a first mode period of 1 second. Further suppose that your design spectrum has a value of 0.3g at T = 1 second. then for scale factors of 0.25, 0.5, 0.75, 1.0, and 2.0, the corresponding first mode spectral accelerations would be 0.075, 0.150, 0.225, 0.300, and 0.600.
Tim Huff