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Thank you very much. Your comments are very helpful to a beginner like me.

If the mass is same at all nodes, the eigen vectors look correct. Now, instead of lumping mass, I assign different mass at the nodes on the floors to create eccentricity. The eigenvector values in X and Y direction are still the same. It is may be because the eccentricity is same in both direction a...

Thank you... I have checked my model many times. The only problem seems to be in defining the center of mass (CM). My building is symmetric in plan and to create eccentricity, the CM is shifted in both directions by 10% of plan dimension. I did this by lumping all the floor mass to the node defined ...

Hi, Thank you for the reply. Is changing the values of Rz in mass command the correct way? mass 1001 0.49208 0.49208 0.49208 0 0 2657232000 mass 2001 0.45783 0.45783 0.45783 0 0 2472282000 mass 3001 0.45091 0.45091 0.45091 0 0 2434914000 mass 4001 0.45091 0.45091 0.45091 0 0 2434914000 I want to inc...

Thank you for the reply. Yes, I also expected all the lines to be same, but in some modes the 1st and last line results are different from the others. The above results are for rotational mode shapes and are not normalized. Also, the values obtained from the eigenvalues command with and without full...

hello,

How can I vary the floor moment of inertia (Io) in opensees?

Dear All, I am trying to do modal pushover analysis of asymmetric building. For this I need the translational mode shape vectors (phix and phi y) and rotational mode shape vectors (phi θ). I use the following code to get these values. for { set k 1 } { $k <= $numModes } { incr k } { recorder Node -f...

Thank you for the information. :) When I use pattern command to give elemental loads then, the period before and after gravity analysis for elastic section varies. For example: pattern Plain 101 Linear { #Column eleLoad -ele 1 -type beamUniform 0 0 -$SelfUDLColB eleLoad -ele 2 -type beamUniform 0 0 ...

Thank you for the reply. Yes,it is an 8-story RC building. And I am trying to do modal pushover analysis, so the accuracy of time period and mode shapes is very important. Considering elastic section, The time periods before gravity analysis are: T1= 1.387s , T2=1.344s , T3=0.430s , T4=0.417s , T5=0...

Hi,

I am creating a 3D asymmetric model in opensees. And when i run the eigen analysis before gravity analysis, opensees gives one set of time periods while runnig the eigen analysis after gravity analysis results in another set of time period. What might be the possible error.
Please help.....