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Thank you very much Dr. Frank~ The problem has been solved. Actually I first tried to reduce the time step to an extremely small degree. However, convergence cannot be achieved until I increase the nodal mass in rotational direction to a certain degree. Although the convergence problem of the typica...

Hello, I tried to analyze an elastic cantilever beam by using central difference method but got very weird results (deformation increases to unreasonably large level). But I can get good results if newmark method was applied using the same code. THANK YOU VERY MUCH in advance if you can help me. # -...

Thank you for your reply Frank! But the only two DOFs for the 2D zerolength element are both rotational DOFs, I think there's actually a way to tell the system which DOF it means. There are some other elements such as Joint2D element which does not follow the "x y Rz" or "x y z Rx Ry Rz" DOF rule ei...

Hello, I made a new element and I tried to make a new recorder to record something that cannot be done by the exsiting recorders. I browse the OpenSees developer folder and found SumElementForcesRecorder.cpp which is a demonstration of new recorder. The essential part of the recorder seems to be "co...

Thank you for your reply Frank! I was doing the same as what you said. I made the output matrix be 6x6 and constrained the translational DOFs of node 2 in OpenSees input TCL script (using "fix 2 1 1 0" command). It worked fined but I actually need to build a much more complex model with many externa...

Hello, I am trying to make a new 2D element which containes 2 nodes and has 4 degrees of freedom (2 translational DOFs and 1 rotational DOF for the first node and 1 rotational DOF for the second). Therefore the stiffness matrix of the element is 4 by 4. But how can I tell global stiffness integrator...

Dear fmk: I tried to add new material "elasticPPCPP" in OpenSeesDeveloper package. I followed "WindowsInstructions.txt" exactly and successfully compiled the dll. However, when I ran "example1.tcl", The prompt windows shows "ElasticPPcpp unaxial material - Written by fmk UC Berkeley Copyright 2008 -...

Hello, I have a question about commitState(). As you can see in the code below, "theMaterial" points to "commitState()", but what class does this "commitState()" belong to and why the name of class does not need to be stated? Thank you in advance! ------------------------------------------------ Tru...

I have a question about the usage of parentheses and square brackets in OpenSees's code. The following code is a small section from the OpenSees source code, I guess the both "connectedExternalNodes(0)" and "theNodes[0]" means the first cell of "connectedExternalNodes" and "theNodes" array respectiv...

Hello, I made flexibility based fiber beam-column element program but it was found hard to converge in section level. I set the convergence criteria as the ratio of (absolute sum of risidual section force) to the (absolute sum of the section force applied at the first step of state determination ite...

Hello, I have a question on displacement control algorithm. According to some iteration based displacement control algorithms, they seem to be indepentent from newton raphson or newton iteration method. But in Opensees, using displacement control with newton raphson or newton method takes different ...

hello, I was trying to find out the displacement contorl theory and I found the following link in OpenSees site: http://opensees.berkeley.edu/wiki/index.php/Displacement_Control However, the explanation of the theory seems to be too short. Can anyone tell me the reference in which more detailed info...

Vesna, thank you for your quick reply!

I meant when performing a pushover analysis, the pushover curve will go up and might reaches peak and then goes down (negative slope), how does OpenSees calculate when the pushover curve goes into negative slope?

Thank you again for your help!

Thank you for your quick reply vesna!
Actually I know exactly what to do in OpenSees, just what I want to know is the theory, can you tell me which theory OpenSees uses for
1. Displacement control method
2. derivation of nonlinearBeamColumn
3. Negative post yield treatment

THANK YOU AGAIN!

Hello, I want to konw the detailed principle of displacement control based pushover of a nonlinearBeamColumn, and I know that there are some different technique to treat negative post yield behavior and different displacement control methods, please tell me or give me some references showing which m...