modeling concrete01

[semon]

Hi everyone,

I am trying to model concrete01 for my project. I found references (Manders model) on calculating the maximum compressive strength and strain at maximum strength of confined concrete using 28 days compressive strength, but I could not find reference on calculatin crushing strength and strain at crushing strength. The codes below is what I am thinking of using. Could anyone give me reference on finding those two values? I would appreciate your help.

set fcc23 -4.818717; # 3500 psi Concrete
set Ecc23 [expr 57*sqrt(-$fcc23*1000)]; # Elastic Modulus
set epscc23 -0.002591; # Strain at Maximum Strength
set fccu23 [expr 0.7*$fcc23]; # Crushing Strength
set epsccu23 -0.01; # Strain at Crushing Strength

uniaxialMaterial Concrete01 $matTagConfConcrete23 $fcc23 $epscc23 $fccu23 $epsccu23;

Thank you

[vesna]

In Mander's paper form 1988 you can also find a formula for crushing strength.

This formula for crushing strain may be useful:

epsilon = 0.004+0.14*(rho_t)*fys/fc'

where rho_t is the ratio of transverse reinforcement, fys is the yielding strength of transverse reinforcement and fc' is the maximum compressive strength of plane concrete.

[semon]

Thank you Veshna for your quick response. I appreciate your help.

[semon]

Hi everyone,

I am trying to run a bridge model without guide angle, key plates and bearing, but I am getting the following errors after 16 seconds.


DirectIntegrationAnalysis::analyze() - the Integrator failed at time 18.8
WARNING - ForceBeamColumn3d::update - failed to get compatible element forces & deformations for element: 244(dW: << 0.00261842, dW0: 2.41547e+015)
Domain::update - domain failed in update
OpenSees > analyze failed, returned: -2 error flag
WARNING - ForceBeamColumn3d::update - failed to get compatible element forces & deformations for element: 244(dW: << 0.00261842, dW0: 2.41547e+015)
Domain::update - domain failed in update
Newmark::newStep() - failed to update the domain
DirectIntegrationAnalysis::analyze() - the Integrator failed at time 18.8
WARNING - ForceBeamColumn3d::update - failed to get compatible element forces & deformations for element: 244(dW: << 0.00261842, dW0: 2.41547e+015)
Domain::update - domain failed in update
OpenSees > analyze failed, returned: -2 error flag
WARNING - ForceBeamColumn3d::update - failed to get compatible element forces & deformations for element: 244(dW: << 0.00261842, dW0: 2.41547e+015)
Domain::update - domain failed in update
Newmark::newStep() - failed to update the domain
DirectIntegrationAnalysis::analyze() - the Integrator failed at time 18.8
WARNING - ForceBeamColumn3d::update - failed to get compatible element forces & deformations for element: 244(dW: << 0.00261842, dW0: 2.41547e+015)
Domain::update - domain failed in update
OpenSees > analyze failed, returned: -2 error flag
WARNING - ForceBeamColumn3d::update - failed to get compatible element forces & deformations for element: 244(dW: << 0.00261842, dW0: 2.41547e+015)
Domain::update - domain failed in update
Newmark::newStep() - failed to update the domain
DirectIntegrationAnalysis::analyze() - the Integrator failed at time 18.8
WARNING - ForceBeamColumn3d::update - failed to get compatible element forces & deformations for element: 244(dW: << 0.00261842, dW0: 2.41547e+015)
Domain::update - domain failed in update
OpenSees > analyze failed, returned: -2 error flag

The model runs with the bearing, guide angles and key plates perfectly, but then I had to change the integration points along nonlinear element and increase the integration points to make run. Is there any problem with the model? What could I do to make it run?

Thank you

[vesna]

Element 244 is failing to converge. You can try several things:

1. change number of iteration and tolerance for the element
2. make sure not to have more that 5-7 integration points at that element
3. try some tweaks on the section that you assign to that element (make sure no to have too many fibers)
4. if none of above is working replace force-based with several displacement-based elements

[semon]

Thank you so much. I had same kind of problem before and changed the integration points to 2 or 3 as required. It ran fine, and now I want to remove guide angles, bearings and key plates. It is again showing me the same kind of errors. Why this is happening again and again when I fixed the problem?