seismic analysis

[alperturan]

Hi

I am beginner of Ansys, I was trying to make a 2D analysis of soil domain. I finished my model and I wanted to solve it using a table array which includes 10 rows and 2 columns. first column represents time whereas the second one includes displacement values. then I came to solution control panel and there is a place " time at the end of load step" I wrote there the last time of my time history.
making automatic time stepping option on I entered the "number of substeps" as the number of the data in my time history.

when I make solution It gives the result for only last step.

can anyone help me on it?

thanks

 

[Drej]

The default in ANSYS is to save the last substep results only. You need to add the command:

outres,all,all

or go to:

Main Menu>Solution>Analysis Type>Sol'n Controls>Basic

See the help file for more details. There may be more issues with your input which you might come up against when you look at the results. I'm thinking of the number of substeps. This has to be based on the natural frequency of your structure, not the number of data points you have. It sounds as though you have picked a number (10 substeps) which may be okay. Instead of number of substeps, I would personally use the command (this is a general example only):

deltim,<t>,<min>,<max>

where t = 1/20 * f

f = natural frequency of interest
min = t/10
max = 2*t

The help file has more details on this (Structural Guide> Chapter 5. Transient Dynamic Analysis>5.10. Other Analysis Details).


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[alperturan]

hi drej

despite I did what you said above. I can get only 1 result.
I selected the option " give results in each Nth substep" and choosen N=1. then it gives a single result again regardless of what you select tume at the end of loadstep.
It simply takes the first displacement value in table and ignores the rest.

I made table of 10*2 (time vs displ) and I want ansys to read each row seperately and do an earhtquake time hist analysis.

I will appreciate more help

regards

 

[Drej]

In the "Basic" tab you should choose "all solution items" and "write every substep". Make sure you have specified the following items:

time,# ! # = some time MORE than the total time in your time history
d,<nodes>,<label>,%table% ! e.g. if your table is called XYZ then %XYZ%


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[alperturan]

hi drej I did what you said and got the solutions. now they are readily processable. But I anlyzed a 1D soil column which means a 1m*30 m column of which sides are restrained in Y diection but free to move in X direction. then I applied seismic shaking to the base of soil column which represents bedrock motion.

I used drucker prager non-metal nonlinearity with Cohesion 15, friction angle 5 and flow angle 5 (associated flow condition). but when I get solition the motion at the base of column was the same as that on the top. But other FE softwares for soil analysis give very different results. motion applied to the base should be amplified in this kind of soil. there is a closed for solution for this problem but what I calculated using ansys drastically far away from these results.

can you give me some more advices to go further.

regards.

I used E=6500 and poissoin ratio=0.4