[MARS-UD-100] Update of shear facet failure feature and LDPM formulation

[licyjiandan]

Hello everyone,

Following Weixin’s previous post, there are now a couple of updates for the shear facet failure calculation and LDPM formulation.

The tet element level calculation of shear facet failure has now been removed. Instead, the shear facet failure calculation is now written in the constitutive laws in mtMLdpmUD in MARS-UD-100. You can use the up-to-date version of MARS library and compile with the updated MARS-UD-100. In your input file, you need add a FacetFailure flag to activate the shear reduction feature:
UserDefinedObject CONC M-LDPMUD {
…
FacetFailure {
ReductionFactor on
}
…
}
An example input file is attached.

Another modification in the mtMLdpmUD file is that three old facetfailure flags, as shown below, are now commented:
// Facet Failure Definition
// s0 = peak effective stress
//if (tmp > 0 && Stot < s0 * FacetFailureRelStress ) {
// stv[15] = -1;
//}
// Shear strain criterion in tension
//if (epsT > FacetFailureShearStrain) {
// stv[15] = -2;
//}
// Shear strain criterion in compression
//if (epsT > FacetFailureShearStrain) {
// stv[15] = -2.5;
//}

Also, the work of Chiara’s paper about the simulation of concrete failure under confinement is now implemented in the mtMLdpmUD file. The calculation of hardening modulus (Kcc in the code) is modified. A new variable dk3 is defined to calculate the new Kcc. Note that this dk3 is also added as a new variable in the mtMLdpmUD.h file. The title of Chiara's paper is "Simulation of concrete failure and fiber reinforced polymer fracture in confined columns with different cross sectional shape" for your reference. Sorry it is too large for me to attach in this post.

In the attachment there is also a ppt file showing the comparison between the simulation results using current MARS-UD-100 with shear reduction feature and the results without shear reduction feature, as well as the results using LDPM Concrete Material Model V5 in the Mars library. It has to be noted that, in MARS-UD-100, the calculation of reduction factor uses the inelastic strain and is up-to-date, while the reduction factor calculation in V5 still uses the total strain.

It has to be noted all above mentioned modifications will mainly affect the simulation of concrete failure with large deformation and under confinement. The simulation of unconfined test or fracture test will be little affected.

Chenyang Li