APDL Transient Analysis Only Registering 1st Acceleration Step
louis2222
Member
Hi there, I am having some trouble in ANSYS!
Short story: I am struggling to get transient analysis load steps (in the form of acceleration) to work. Please could you have a look at my code and let me know if something is obviously wrong? It is only reading the first acceleration step for the x axis, then applying it to both x and y, and then staying at a constant acceleration after that.
Long story: I am trying to carry out transient analysis on a 3 story structure using acceleration data (gathered experimentally) to excite the structure at its base. The structure is mounted on an xy axis shaking table to simulate earthquakes (so I am assuming it is only constrained in the z direction at the base, as well as within the xy limits of the table). I am importing the acceleration data into a table, and then using a do loop to read the accelerations at each point to complete the transient analysis, as you can see in my code below. The problem I have is that ANSYS is only applying the 1st acceleration step. The remaining analysis is just for free oscillation. You can see this in the photo attached in the "Bot_Y_ACCEL" line. It moves to the first load step (in this case 0.5), then stays there. The rest of the lines just oscillate about this straight line. This is just impulse response, however I need to analyse sustained and varying accelerations!
Any help at all would be so appreciated and you might just save my master's project. Many thanks in advance!
/FILENAME,Transient_Test
/SOLU
FILE = 'data' !Enter data file name
DT=0.00781 !Time interval (1/128 seconds)
SKIP = 0 !Enter number of lines to skip
/INQUIRE,NUMLINES,LINES,FILE,TXT !Finds number of lines
READ = NUMLINES - SKIP !Calculates how many lines to read from data file
*DEL,ACCEL,,NOPR !Deletes previous instances of ACCEL
*DIM,ACCEL,TABLE,READ - 1,2 !Create a table for xy acceleration data
*TREAD,ACCEL,FILE,TXT,,SKIP !Read data from FILE.txt into ACCEL table
ACEL,,,9.81 !Gravity
ANTYPE,TRANS !Transient analysis
TRNOPT,FULL !Full method
TIMINT,ON,STRUC !Transient effects (inertia/mass) ON for structural DOFs
KBC,1 !Stepped loading for transient analysis
OUTRES,ALL,1 !Output everything
OUTPR,BASIC,ALL, !Basic solution print
NT=READ !Number of data points
NSUBST,1,,,1
*do,i,1,NT !Running from 1 to NT all data points
TIME,i*DT!Calculate time vector by DT
CMSEL,S,COLUMNS!Select column component
CMSEL,A,FLOORS!Select floor component (in other words all components of my model)
NSEL,S,LOC,Z,0!Select all nodes at z = 0 to apply acceleration to
D,ALL,ACCX,ACCEL(1,i)!Apply x acceleration
D,ALL,ACCY,ACCEL(2,i)!Apply y acceleration
ALLSEL!Select all nodes to complete solution
SOLVE
*enddo
Comments
Hey Louis, did you solve the problem?
I have the same problem now: i have a temperature dependig on the time and also the gravity in y-direction. My model only solves the effect of the gravity before the first temperature step and after that, it doenst change. Do you know, how i can solve this or can you tell me how you did it?
Hope you see this,
Thank you
@louis2222 , you solve it ??
FINISH
/CONFIG,NRES,100000
/PREP7
DAMPRATIO=0.05000
*SET,NT,2400
*SET,DT,0.02
*DIM,AC,,NT
*VREAD,AC(1),seismic_record,TXT
(F8.5)
/SOLU
ANTYPE,TRANS
TRNOPT,FULL
*DO,I,1,2400
ACEL,AC(I),0,0
TIME,(I)*0.02
OUTRES,ALL,ALL
SOLVE
*ENDDO
FINISH
this code will help you
you mat use
/SOLU
DELTIM,0.02
ANTYPE,TRANS
TRNOPT,full
AUTOTS,ON
NSEL,S,LOC,Z,-38,375
CM,NUPP,NODE
OUTRES,ALL,ALL
TIMINT,ON
TIME,0.02
ACEL,,,9.8
NSEL,S,LOC,Z,-38,375
D,ALL,ACCX,0.035672
ALLSEL
SOLVE
TIME,0.04
ACEL,,,9.8
NSEL,S,LOC,Z,-38,375
D,ALL,ACCX,0.009702
ALLSEL
SOLVE
TIME,0.06
ACEL,,,9.8
NSEL,S,LOC,Z,-38,375
D,ALL,ACCX,0.041944
ALLSEL
SOLVE
TIME,0.08
ACEL,,,9.8
NSEL,S,LOC,Z,-38,375
D,ALL,ACCX,0.04284
ALLSEL
SOLVE
TIME,0.1
ACEL,,,9.8
NSEL,S,LOC,Z,-38,375
D,ALL,ACCX,0.0106526
ALLSEL
SOLVE
I would keep it more simple so no do loops. In this way you just apply the time variation of the load as a table (Workbench uses something like this in Str. Dyn.). You need also to split up the acceleration data file to x-direction filex and y -direction filey.txt. That is very easy though.