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Hi fmk,

How about the moment positive directions at element ends?

Best,
Tim

fmk wrote:
> yes.

Thanks so much Frank, I got results but definitely they are not correct. I changed the values of damping coefficients but the results did not change accordingly...

We have a bunch of nonlinear springs to model the behavior of abutment components such as foundations, shear keys, bearings, deck pounding, etc. Now we are trying to investigate the influences of soil radiation damping on the bridge responses. It seems that there is a issue to implement the dashpot into the nonlinear spring groups. Even when it is connected in parallel with one of the nonlinear spring (this resultant parallel element is connected in series and parallel with other nonlinear springs), I am having the deck displacement in one direction that is larger than the case when no damping is considered, which I think is counter-intuitive.

I appreciate it if you have any thoughts to tackle this issue.

Yazhou




fmk wrote:
> if you are getting results, then you can .. whether the results are correct
> or not is something else .. looking at the code in the Maxwell model, i
> would doubt it .. this of course assumes young Prof. Dimitrios Lignos got
> it correct .. perhaps you should send him an email. He is now is
> Switzerland.
>
> int
> Maxwell::setTrialStrain(double strain, double strainRate)
> {
> // Set Total Strain
>
> Tstrain = Cstrain;
> Tstress = Cstress;
> Ttangent = Ctangent;
>
> // Determine change in strain from last converged state
>
> double dStrain = strain - Cstrain;
>
> // Constant based on Viscous Damper Viscocity C and Axial Stiffness K
>
> double tR = (C/pow(L,Alpha))/K;
>
> // Integration Constants as a function of incremental time dt
>
> // Note: The integration time dt = ops_Dt is coming in from the
> OPS_Globals
> double A = Tstress * ( exp(-ops_Dt/tR) - 1.0);
> double B = (K/2.0) * (1.0 + exp(-ops_Dt/tR) );
>
> // Incremental Stress Calculation (considers the history of strain in A
> and B
> double Dstress = A + B * dStrain;
>
> // Total Stress Calculation (Tstress) is increment Stress Plus Previous
> Total Stress
> Tstress = Dstress + Tstress;
> Tstrain = strain;
>
> // double DTangent = Tstress/Tstrain;
>
>
> return 0;
> }

Hi All,

Is there a way in OpenSees to connect a linear dashpot with a nonlinear spring in series? I have tried to assign two elements for each of these two materials and connect them in series. However, the results seems not correct to me. Any ideas?

Thanks,
Yazhou

In the case with asymmetric material (i.e., the tension and compression sides have different backbone curves), does the node order (i.e., the ith and jth node) matter in the definition of zero-length element? If so, what is the basic rule?

Thanks in advance,
Yazhou

Dear all,

I am using the py spring material that I found is much more convenient to call using the version 2.2.0. Would it be possible that anyone can send me this version (64 bit) to yxie@rice.edu? Thanks!

Hi Fmk,

I am using the py spring material that I found is much more convenient to call using this version. Would it be possible that you can send me this version with 64 bit to yxie@rice.edu? Thanks!

Hi All,

I conducted a free vibration analysis of a rocking column with no damping included, geometric nonlinearity is modeled as corotational transformation and corotational truss elements at rocking supports. Newmark method is used as the integrator. However, the amplitude of the free vibration differs in every circle. Does anyone know the reason? Ideally free vibration amplitude should be constant since no damping is modeled.

Thanks in advance,
Yazhou

Hi all,

I was trying to model the behavior of a free standing rectangular rocking block with a concentrated mass. Since rocking is equilibriumed in the rotational direction, the determination of the rotational mass is critical. I wonder how OpenSees considers this, which value should I use for the rotational mass? I.e. if we consider the equilibrium to the toe at the block bottom, mass inertial = 4/3 m R^2, where R is the distance between the mass point to the toe. While is this the correct value I should use? I tried this and the solutions is not charming...

Thanks in advance,

Yazhou

Thanks Frank, I tried the corotation truss element and it works!

Hi All,

I am trying to model the rocking column on rigid base using compression only materials at the rocking interface, I used zero length elements with ElasticPP spring material in the vertical direction. While since it is a large deformation problem, the spring response was not correct. So is there any other element that I can use for the compression only material, while also considers large deformation, e.g. geometrical transformation in beam column elements?

Thanks,
Yazhou

Hi Everyone!

I am using UiSimCor to connect OpenSees for my hybrid simulations for a bridge including SSI. At each time step UiSimCor just read the restoring force from OpenSees and input the forces to my condensed hybrid model. And I have to compose a damping matrix for my UiSimCor model separately, for the structural damping part I use the same Rayleigh Damping coefficients and it turns out my UiSimCor model has the same response comparing to the whole OpenSees Model.

While since I have to use several linear dashpots to model the SSI effects. I do not know how these dashpots affect the damping matrix and stiffness matrix in OpenSees. From common sense say if I add a dashpot with 'c = 10e5' between node 100 and 101, I thought the damping matrix will be changed to:
C new (DOF of node 100) = C old (DOF of node 100) + 10e5; C new (DOF of node 101) = C old (DOF of node 101) + 10e5; and the stiffness matrix will not change.

Is this correct? I changed my code in this way it seems the responses are different.

Thanks for any helps.
Tim