The OpenSees Community

Dear Sir or Madam, I want to do the modal analysis and obtain normalized mode for my Opensees model. I saw a command "printA", and tested it in the most simplest example (elastic SDOF) in Opnesees example manual. The result is 3X3 matrix as follows: "679.495 0 146771 0 3.5225e+010 0 1...

I have a same problem with modeling pins in two horizontal direction in 3D moment frame. If I use equalDOF to connect pins, two nodes are isolated. If I use zerolength element, it ran out of memory. I already tried UmfPack and SparesSYM. They don't work neither. Hope that we can have a positive solu...

Hi All I have 3D 20 story moment frame. And I have lots of pins. The way I model pin is defining two note in the same location. And use zero length element to connect these two points. Direction 1 2 3 4 strong material, direction 5 and 6 very small stiffness. (PS: I try to use EqualDOF to model the ...

Many thanks for your reply, Vesna. I also send you my model. Actually, element 1576 is column element. It works perfectly when it's 10-story-building. But when it goes to 20-story-building, there're hundreds of similar warning in different columns. I'm thinking whether it is out of the capability of...

Hi all I model a 20 stories Moment Frame 3D structure in Opensees. The details are as followed: Column: Fiber section, use nonlinearbeamcolumn element, using steel02 materials Beam: 1) elastic beamcolumn element; 2) zerolength element in both ends, using bilin materials analysis command: 1) constrai...

[quote="fmk"]The 3 factors are for current stiffness, last committed stiffness and initial stiffness.

The text book only deals with elastic damping problems, in which case they are all equal.[/quote]

Many thanks for your prompt reply.

Hi all In rayleigh damping, D = $alphaM * M + $betaK * Kcurrent +$betaKinit * Kinit + $betaKcomm * KlastCommit What do these three stiffness mean? Is it for nonlinear? If it's linear, are these 3 coefficient the same? In Chopra, C=a0*m+a1*k, what's this k for? Initial? Committed or current? Many tha...

Hi Frank, many thanks for your contribution to Opensees. I still have question for Silvia's note. 1) No matter how many Dof, we just need to define eigen 1 and eigen 3. Why 1st and 3rd? Is it just convenient? 2) Why we just make beta Kcomm 1, and set current and initial betaK 0? Why do we need 3 K s...

Hi, all

I just write a loop for my analysis. The file is about 15 MB. And I try to execute it. Then it reply " invalid command name ample". When I separate the files, it can run. Is it too big for Opensees to run? Thank you.

I got it. Many thanks, Slvia!!!

Thanks again for your help. Silvia. I still want to know what do you mean of connecting the dots. The ground motion has 3000 points, the dt is 0.01, we get 3000 points of response. If my analysis dt is 0.005, the opensees will take 6000 points in calculation, we have 6000 points of response. How doe...

Thank you for your prompt reply, Silvia. Actually, I want to figure out how Opensees interpolates. For example, the ground motion is 1 、1.3 、 1.4 、1.7、 2.0 ，the ground motion dt is 0.01. If I want the analysis dt is equal to 0.005. Will the opensees interpolate the data of the average value between ...

Hi,all. I have transient analysis that is running at a time step of 0.015 My input acceleration file has a time step of 0.01 How does OpenSees interpolate this acceleration data set?? I'm told that it's linear interpolation. However, I still want to prove it. I try to record acceleration of the poin...