Displacement control method used in OpenSees

[buddhasarah]

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 method OpenSees is using.

The principles I need to know
1. Displacement control method used in OpenSees
2. derivation of nonlinearBeamColumn
3. Negative post yield treatment used in OpenSees

THANK YOU VERY MUCH in advance!

[vesna]

To do pushover you need to monotonically increase the load acting on your structure to push your building to a target displacement. Using "load pattern" you will define the load pattern for your structure and using Displacement control integrator you will specify the increments of displacements to which you want your structure to be pushed in each step of analysis. To capture the softening of your structure you have to use BandGeneral system solver.

[buddhasarah]

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!

[vesna]

1. The basic theory about displacement control integrator you can find here: http://opensees.berkeley.edu/wiki/index ... nt_Control
2. There are several references about force-based beam column element and they are listed here: http://opensees.berkeley.edu/wiki/index ... mn_Element
3. What do you exactly mean by negative post-yield treatment?

[buddhasarah]

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!

[vesna]

It depends on the solver that you use to solve your system of equations. When you define the system (http://opensees.berkeley.edu/wiki/index ... em_Command) you define the way in which the system of equations is solved.

[yueyu204]

Thanks for sharing, great tips!

[rasoulazadi]

hi dear vesna
my load pattern is as follow:
pattern Plain $y Linear {



load 12 $p1 0 0
load 22 $p1 0 0
load 32 $p1 0 0
load 42 $p1 0 0
load 52 $p1 0 0
load 62 $p1 0 0



}
that p1 ,....,p6 are loads that in each step increases
if we use the integrator LoadControl $incrSpost 1 $incrSpost $incrSpost
in the next step of analyse how was the load pattern and what is the effect of $incrSpost value .
tanks

[vesna]

To understand the way the load is applied on to the structure check this: http://opensees.berkeley.edu/wiki/index ... d_analysis.

[rasoulazadi]

hi dear vesna
tanks for replay
if we use from integrator LoadControl $incrSpost 1 $incrSpost $incrSpost
in the loop value of landa is always $incrSpost or will be increase in each step
regards

[vesna]

For the current (nth) step of analysis, λn = λn-1 + λ.