how apply accelerogram in Ansys?
how apply accelerogram in Ansys?
(OP)
I want apply accelerogram to the base of my structure in a transient analysis, it's possible?
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how apply accelerogram in Ansys?
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how apply accelerogram in Ansys?how apply accelerogram in Ansys?(OP)
I want apply accelerogram to the base of my structure in a transient analysis, it's possible?
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RE: how apply accelerogram in Ansys?
RE: how apply accelerogram in Ansys?
RE: how apply accelerogram in Ansys?
-Brian
RE: how apply accelerogram in Ansys?
RE: how apply accelerogram in Ansys?
it depends: in v.11.0 Ansys has added the ability to handle accel BC in a transient analysis.
If you're using v.10 or lower, then yes, unfortunately you will have to shift from accel to displacement, and this won't be very easy...
RE: how apply accelerogram in Ansys?
RE: how apply accelerogram in Ansys?
Can you not integrate your data twice with respect to time and get the displacement for each point? I don't have any references handy here at home but I seem to remember this being fairly simple. You should be able to do this in Excel or even using the *VXXX series of commands within Ansys. Once you have this, you can simply apply the displacement using tabular data of displacement vs. time within Ansys.
-Brian
RE: how apply accelerogram in Ansys?
ah, sorry, I misread the post, I was thinking about the normated spectra for earthquake as in the italian D.M. 14/09/05...
Yes, as Stringmaker says, if you have a time-dependent acceleration history, then you can perform a double integration. You will have only one "problem" in assigning appropriate values for the integration constants, but you can think about them as being initial velocity and displacement, so I believe you can fix it to zero.
But the time history is discrete, it's not written as a function, so you will have to make some assumption in re-building a piecewise function connecting groups of time points: the simplest is to connect only two successive time points in a linear fashion, so if you have n time points you will build n-1 functions of the type ai=mt+q, then you will pass to velocities vi=(1/2)mt^2+qt+c1 (where you can set c1=0 if you consider that the earthquake begins from a "stillstand" state), and lastly to displacements si=(1/6)mt^3+(1/2)qt^2+c1t+c2 (where you can drop the two last terms). The displacements have to be considered as "incremental": at time point t, the displacement s[t] is the sum of s[t-1] and si, and so on. It's tedious to do by hand, but almost immediate with Excel.
Hope this helps and that I didn't miss something...
Regards
RE: how apply accelerogram in Ansys?
RE: how apply accelerogram in Ansys?
you will have to format a pure-text file as follows, without any header nor comment:
time-value displacement-value
time-value displacement-value
...
Then, in Ansys, go to Parameters -> Array Parameters -> Read From File -> Table
and input your text file, while assigning it to a table-variable.
When it comes to assign D boundary conditions, instead of an explicit value select "existing table" and give the previously defined table name.
You need only one step but many substeps (depending on which is the max response frequency you expect to be significant for your system - in this sense, a previous modal analysis is very helpful).
Regards
RE: how apply accelerogram in Ansys?
Where:
n=number of data points
file=filename
ext=file extension
*dim,time_hist,table,n,1,1,time,x
*tread,time_hist,file,ext
You should be able to export something from excel rather easily. Make sure your file is space (not tab) delimited. Ansys normally doesn't like reading file delimited by anything other than spaces.
-Brian
RE: how apply accelerogram in Ansys?
RE: how apply accelerogram in Ansys?
1- if you use the APDL commands, the syntax given by Stringmaker applies: you can see that the "*DIMensioning" of the table calls "TIME" the first variable and "X" the second one.
2- if you use the graphical interface, as you say Var1 (row) is TIME and Var2 (column) is X (not UX, if I'm not wrong).
Regards
RE: how apply accelerogram in Ansys?
Regards
Michele