I have a question regarding series of earthquake analysis. What I want to do is to study the effect of aftershock.
To do that, I first apply 1st ground motion record to a frame. After 1st record, I apply static correction by performing static analysis with dummy load at any arbitrary node. Then I apply 2nd record. For test, I used two records that are weak enough that the frame remains almost elastic. The response from first record seems to be fine (with very small displacement) but the response of the frame under the second record is very strange, compared with the response of the virgin frame under the same record.
It seems to me that the end of dynamic state of the 1st record response is the initial state of the frame for the 2nd record analysis, although I intended to use a static residual state from 1st analysis as an initial state of 2nd analysis by static correction.
Here is my code
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... create frame
... create recorder
loadPattern 1
...
#do earthquake analysis
...
remove loadPattern 1
loadPattern 2 # dummy load
...
#do static analysis ...
...
remove loadPattern 2
remove recorder
# create recorder
recorder ....
loadConst -time 0.0
loadPattern 3
...
#do earthquake analysis
...