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SO,

the equalDOF cannot be used to "condense out" degrees of freedom.

this still does not explain why I get different results when I put all three DOF in a single command line VS three seperate lines.

I am using the equalDOF command to reduce the number of DOF in my system. I was using an eigen analysis to compare frequencies and mode shapes of the reduced model to that of the full model. When I reduce 2 of the horizontal DOF's on each floor of the structure, I got good eigen/mode shape results a...

I have asked this same question before, and got no response.

I am running a transient analysis with a time step of 0.0003 seconds and have an input excitation that has a time step of 0.02 seconds. The overall trend of the acceleration record is very near what I expected, however when I zoom in and look at the finer detail, the output is not what I would have ...

I have transient analysis that is running at a time step of 0.0003

My input acceleration file has a time step of 0.02

How does OpenSees interpolate this acceleration data set for the smaller analysis time step???

I am using nonlinear rotaional springs (hinges) in an analysis. However, my model is a steel moment resisting frame, not concrete. If you are interested in my code let me know.

andrew

I am modeling the SAC 3-story structure. I am currently comparing the results to a FE model created in MATLAB. The results are very similar. The only difference in the two models that I can find is that there is currently no damping being applied to the zero-length elements or the truss elements. (i...

I have a model with several truss and zero-length elements. I was looking through the message board and discovered that these elements are not affected by the stiffness portion of Rayleigh damping. I think I need to define a value for $eta (damping tangent) in the truss and zero-length material defi...

I am running a dynamic analysis on a 3-story 4-bay nonlinear frame, and am having to use a very small time step for the simulation to run successfully. Does the following methodolgy look correct, or is there a better "solver", that would enable the use of a larger timestep??? set inctimest...