how to consider cumulative damage in OpenSees

[wcq19811982]

Hello everybody,
In the nonlinear analysis for the frame structure,
several seismic waves in sequence were input to the frame model.
With the consideration of the cumulative damage in the structure,
time was rested to be 0.0 with loadConst command after each seismic wave input completed.
But it is found that the story displacement with the consideration of cumulative damage is smaller than that without consideration of the cumulative damage.
It is justly contrary to my understanding. What is it to cause this?

[vesna]

Are you using the same seismic wave each time? It is not clear to me what results you are comparing.

Make sure to use materials that allow for degradation and damage.

[wcq19811982]

Dear vesna,
Thank you for your reply, the model is a two-bay and two-span and three-storey frame structure.
The Concrete02Materal and Hysteretic Material are used to represent concrete and steel bars, respectively. The Displacement-Based Beam-Column Element was used in the model. Different seismic wave is used each time. I used two kinds of ways to input seismic wave, one is that all seismic waves were linked together to input for the consideration of cumulative damage, one is that only one seismic wave was input without the consideration of cumulative damage. The storey displacement is compared, but it is found that the story displacement with the consideration of cumulative damage is smaller than that without consideration of the cumulative damage. So I want know what it is to cause the result?

[vesna]

Can you show me your concrete02 and hysteretic materials?

If you want to see the effect of the cumulative damage by comparing maximum displacements you should repeat the same wave several times and compere it with the maximum displacement from only one wave. Also make sure that your wave is strong enough to induce nonlinear deformations.

[wcq19811982]

###define basic units:length:meter;force:N;time:second

Dear vesna,
Very grateful for your help, the material parameters are listed as follows:
####Concrete material parameters
uniaxialMaterial Concrete02 11 -38481816 -0.00299 -7696363 -0.14995 0.047 384818 17655e5;# Side column
uniaxialMaterial Concrete02 21 -39539088 -0.00308 -7907817 -0.15407 0.037 395390 17655e5;# Corner column
uniaxialMaterial Concrete02 31 -38018831 -0.00296 -7603766 -0.14815 0.070 380188 17655e5;# Beam1
uniaxialMaterial Concrete02 41 -38958953 -0.00304 -7791790 -0.15181 0.07 0389589 17655e5;# Beam2

###Reinforcing bar parameters
uniaxialMaterial Hysteretic 9 274.11e6 0.00151 3015.21e5 0.00181 205582500 0.00226 -274.11e6 -0.00151 -3015.21e5 -0.00181 -0.00226 -0.00226 1.0 0.2 0.0 0.0
uniaxialMaterial Hysteretic 10 247.0e6 0.00181 2717.00e5 0.00200 185250000 0.00250 -247.00e6 -0.00181 -2717.00e5 -0.00200 -0.00250 -0.00250 1.0 0.2 0.0 0.0

whether there is any problem about above defined material parameters?
thank you

[2015James]

I wonder if you use damage index or some other ways consider the cumulative damage?

[vesna]

I noticed two things:
1. In concrete material for beam2 you have tensile strength of 0389589. Most of your input data is input as integers. When using tcl it is always better to define them as floating-point numbers (e.g. 389589.0 instead of 389589). If you add, subtract, multiply and divide two integer numbers in Tcl the result is an integer. I would also start with Concrete01 and letter switch to Concrete02.

2. I noticed that the third point on the negative side of Hysteretic material has very small stress.

Yes, you can use damage index to consider cumulative damage.

[wcq19811982]

Dear vesna, Very grateful for your help，I will try according to your suggestions

[wcq19811982]

Dear vesna,
In my script code, the dispBeamColumn element is used to analyze the model,
it is convergent. However, if the nonlinearBeamColumn element is used to replace the dispBeamColumn element,
it is not convergent. Could you help me explain why it is so?
Thank you

[vesna]

DBE is based on displacement-based formulation where the element state is solved in one step. However, FBE is based on force-based formulation where element states is solved through iteration process.

[wcq19811982]

Dear vesna,
Thank you for your reply.
Is it accurate for the results, DBE is adopted instead of FBE assuming convergent to use DBE and not convergent to use FBE.
Thank you

[vesna]

Yes, I do that sometimes too. Just make sure to replace 1 FBE with several (8-16) DBEs.

[wcq19811982]

The same frame structure is subjected to two consecutive excitations of the same seismic wave and the lateral stiffness of the structure degraded. But it is found that the displacement response under the second excitation is smaller than the first. In my opinion, the displacement response should increase under the second seismic excitation. Why the result is contrary to my understanding. Is it relative with the frequency-spectrum of the seismic and basic natural frequency of the structure and the pinching factor of the material model? The Concrete02 Material and Hysteretic Material are used to represent concrete and steel bars, respectively. The Displacement-Based Beam-Column Element was used in the model.

[Forster]

Dear wcq19811982
I have the same problem with you when i use the consecutive excitaions. Have you solve it ?