About handling the recorder.

deepak · Post by **deepak** » Fri Dec 12, 2008 1:30 am

Dear Silvia,
I would like to know how to record the responses only for specified interval of time. For example, if I am running dynamic time history analysis and my ground acceleration data are at time period is 0.05 sec. But I only want to recode the response of the structure at 0.5 sec time step only though I am analyzing for 0.05 sec time step.

Thank you for your time and attention.

arbarbosa · Post by **arbarbosa** » Tue Dec 16, 2008 11:48 am

Try to use the "-dT $dtOutput" option for the recorder and see if it works for you.

deepak · Post by **deepak** » Mon Feb 16, 2009 2:10 am

Thank you Silvia.
I am late for replying your post. Just today, I tried according to your suggestion and I got exactly I wanted.

Thank you again.

Deepak Rayamajhi

qindan_h · Post by **qindan_h** » Thu Apr 16, 2009 7:20 pm

I used -dT 0.01 for my case where the time step for analyzing is 0.0001. The time I got in the recorder time is:

0.0001
0.0102
0.0203
0.0304
0.0404
0.0504
0.0604
..........

In another word, the invertal of time in the file sometimes is 0.0101 and sometimes is 0.01. Why is it not constant 0.01 I set in recorder?

Post by **fmk** » Fri Apr 17, 2009 11:17 am

the deltaT is the time increment .. it records the first at current time (which in your case is end of first analysis 0.001) and the next time to record is when analysis is > last recorded + deltaT.

so live with it or set the time in the domain to -0.01 and do a dummy analysis at time 0.0 with 0 loads to get a recorded line of all zero's.

qindan_h · Post by **qindan_h** » Fri Apr 17, 2009 11:49 am

hi, Frank,

I think you misunderstood my question. I am wondering why the interval of the time, t(n)-t(n-1), is not constant. Since I set -dT 0.01, I expect that the interval of the time in the recorder remains 0.01. In another word, the currnt time point minus the previous time point should be 0.01 always. However, in my case, when I use 0.0001 for analysis and -dT 0.01, I got

t1: 0.0001
t2: 0.0102
t3: 0.0203
t4: 0.0304
t5: 0.0404
t6: 0.0504
...........

t2-t1 = 0.0101, t3-t2 = 0.0101, but t5-t4 = 0.01. Why? (I don't mind the t1 is not zero. )

Thank you very much!!

Post by **fmk** » Fri Apr 17, 2009 12:15 pm

the problem is due to roundoff .. instead of 0.01 use 0.0099999999 or something.

qindan_h · Post by **qindan_h** » Sat Apr 18, 2009 11:49 am

Using 0.00009999999 works. Thank you!!