The OpenSees Community

Dear colleagues,

I have a problem in defining the Uniaxial Material Model for the steel fibers in zero-length section element for the rectangular section column.

Apparently the bond_sp01 model is not applicable for rectangular sections! Please, is there another solution?!

I appreciate your help.

Dear colleagues,

what is the model used to simulate the steel fiber in zeo-length section element for the rectangular section column?!

I appreciate your help.

Dear colleagues;

I want to do a transient analysis and split the increment into two parts.
The first calls for the first file (for a coarse discretization) and the second file (for a fine discretization).

For that the program written below does not work, can you help me please!

for {set i 0} {$ i <= 5} {incr i 1} {
wipe
source 415cyclic5_1.tcl
for {set i> 6} {$ i <= 10} {incr i 1} {
source 415cyclic5_2.tcl
# define ground motion parameters for two file ...

I appreciate your help.

Dears friends,

How can be define 'tension strain in extreme tensile steel fiber' for column fiber FE model ?! Is it defined as follows ?!

recorder Element -file SecSteel.out -time -ele1 section1 fiber -$ro 0. $IDreinf stressStrain (ro=Diameter/2)

Please, your suggestions will be very useful for me.

Dear colleagues,

I am wrapping up Reinforcing Steel material with a fatigue material to use in RC column.

Please, How can i calibrate (or calculate parameters) fatigue material variables for ajusting it for this material?

I appreciate your hep.

I'm looking for how to compute ultimate strain of confined concrete (ecu) with Mander model (Those equations demand a iterative procedure) !!!

I will be very grateful if you can share with me the program for the iterative calculation.

I appreciate your help.

Dear all,

I’m trying to validate a fibre FE model that analyse the cyclic pushover response of 415 RC column of Lehman et al. [1]. In a general way, I followed the modelling strategy proposed by Wang et al. [2].
To model the confined concrete, I used Mander et al. model [3] to compute the compressive strength given by eq. 29. The obtained value is equal to 42 MPa, which gives ɛcc of 0.66% and ɛcu of 1.56%.
Strangely, the obtained values are different to that obtained by Wang et al. [2] (compressive strength of 61 MPa and ɛcc of 1.36% and ɛcu of 1.85%).
Moreover, the FE model does not work in OpenSees when using my values!
The MATLAB script used to compute the compressive strength of confined concrete is given bellow.

Any suggestions please.

[1] D. Lehman, J. Moehle, S. Mahin, A. Calderone, and L. Henry, “Experimental Evaluation of the Seismic Performance of Reinforced Concrete Bridge Columns,” J. Struct. Eng., vol. 130, no. 6, pp. 869–879, 2004.
[2] Z.-H. Wang, L. Li, Y.-X. Zhang, and S.-S. Zheng, “Reinforcement model considering slip effect,” Eng. Struct., vol. 198, p. 109493, 2019.
[3] J. B. Mander, M. J. N. Priestley, and R. Park, “Theoretical stress-strain model for confined concrete,” J. Struct. Eng, vol. 114, no. 8, pp. 1804–1826, 1988.

The matlab script:
% Compute of Compressive Strength of Confined Concrete, f'cc by Mander eq
%f'cc=f'c0(-1.254+2.254*sqrt(1+((7.94*f'l)/f'c0))-2*f'l/f'c0)
s=0.032; %spacing (Column Lehman 415)
Dcol=0.6096;
cover=0.03302;
dbar=0.01588;
dbarT=0.006;
fyh=607;
numBar=22;
Hcol=2.44;
fc0=30.3; % f'c0: unconfined concrete compressive strength
%Vcore=Score*Hcol
%-------------------------------------------
% Ke coefficient given by eq. 14 or 15
% s : center to center spacing or pitch of spiral or circular hoop
% s': clear vertical spacing between spiral or hoop bars
% s : spiral spacing or pitch
s1=s-dbarT;
% ds: diameter of spiral between bar centers
ds= Dcol-2*cover-dbarT;
% Rhocc : ratio of area of longitudinal reinforcement to area of core of section
%------
% Acc: the area of concrete core eq.12
% Area of longitudinal reinforcement
Areinf=(pi*dbar^2)/4*numBar;
% Effectively confined core Diameter (fig.2)
DeffCore=ds-s1/2;
% Ae : the area of an effectively confined concrete core eq. 12
%Ae=(pi/4)*ds^2*(1-(s1/2*ds))^2;
Ac=(pi*ds^2)/4;
Rhocc= Areinf/Ac
% spiral spacing or pitch
Ke=(1-(s1/2*ds))/(1-Rhocc)
%--------------------------------------------
% RhoS: ratio of the volume of transverse confining steel to the
% volume of confined concrete core eq.17
%----------
% Asp: area of transverse reinforcement bar (Formule of Tore in google)
% Asp=4*pi^2*(dbarT/2)*(Dcol/2-cover-dbarT/2);
Asp=(pi*dbarT^2/4);
RhoS=(4*Asp)/(ds*s)
%--------------------------------------------
% fyh : yield strength of the transverse reinforcement
%--------------------------------------------
% f'l: lateral confining pressure on concrete
% f'l is given by eq. 19
f1l=1/2*Ke*RhoS*fyh
%---------------------------------------------
% fc0: Compressive Strength of unconfined Concrete (Experimental value)(MPa)
% Compute of Compressive Strength of Confined Concrete, f'cc (eq. 29)
ratio=(-1.254+2.254*sqrt(1+(7.94*f1l)/fc0)-2*f1l/fc0)
fcc=fc0*ratio

Dear all;
I had this note while running my model RC column;

R is negative in ReinforcingSteel::SetMP()

and then the convergence failed using all methods.
Any idea please!

Thank you so much for your reply.

Dear colleagues.

There is straightforward way to calculate the energy dissipated through hysteretic cycles in cyclic response using Matlab or OpenSees Script?

I appreciate your help.

Dear colleagues;

I want to know how to model the transverse reinforcement when considering buckling and low-cycle fatigue in RC column ?!

I appreciate your help.

Dear colleagues,

For modelling the RC column considering inelastic buckling of reinforcement. Authors use force-based Frame Element (two force-based elements).

Are these two force-based elements modeled by distributed plasticity (nonlinear beam column) or the combination of two formulations (distributed plasticity and concentrated plasticity) ?!

I appreciate your help my colleagues.

Dear colleagues,

I am running a pushover analysis using load-control integrator. I use the following load control procedure,

set Tol 1.0e-12;
test NormDispIncr $Tol 1000 ;
algorithm Newton
integrator LoadControl 10.0
analysis Static
analyze 10

I usually change the 'integrator LoadControl' increment and 'analyze' number of step and errors runs.

UniaxialMaterial::setTrial() - material failed in setTrialStrain()
ForceBeamColumn2d::update() - section failed in setTrial
Domain::update - domain failed in update
LoadControl::update - model failed to update for new dU
WARNING NewtonRaphson::solveCurrentStep() -the Integrator failed in update()
StaticAnalysis::analyze() - the Algorithm failed at iteration: 0 with domain at load factor 10
OpenSees > analyze failed, returned: -3 error flag

I appreciate your help.

Dear colleagues,

To evaluate the OpenSees capabilities for shear-flexion interaction. What is the best way to use. Rotation based shear failure model (RotationShearCurve) with (PinchingLimitStateMaterial) that controls the degrading column behavior
OR
Shear spring at the bottom defined using the limit state Material and limitCurve shear;

What is the best choice to study the effect of shear!

I appreciate your help.

Dear mohammmad,

thank you a lot for your reply.
I am looking for how to define in OpenSees the following command for circular sections ?!!
limitCurve Shear $curveTag $eleTag $rho $fc $b $h $d $Fsw $Kdeg $Fres $defType $forType <$ndI $ndJ $dof $perpDirn $delta>.

I appreciate your help colleague.