11.3.10 Modified Maekawa Concrete Model USRMNL

As an alternative to direct input, the Modified Maekawa Concrete model can be applied as a user-supplied subroutine. Therefore you must specify USRMAT MAEKAW in the input data [§9.4.2] and supply the code for subroutine USRMNL.^11.1This subroutine has the same arguments as the routine USRMAT [§11.4]. However, outside USRMNL DIANA expands the stresses and strains to three-dimensional tensors such that the calculation of stresses from strains can be done for the various element types in a uniform way, whereas USRMAT works with the regular stresses and strains.

    (Fortran)

      SUBROUTINE USRMNL( eps0, deps, ns, age0, dtime, temp0,
     $                   dtemp, elemen, intpt, coord, se, iter,
     $                   usrmod, usrval, nuv, usrsta, nus,
     $                   usrind, nui, sig, stiff )

usrmod

is the user-supplied model name from input table 'MATERI'. For the Modified Maekawa model this name is always MAEKAW.

usrval

are the user-supplied material parameters from input table 'MATERI'. For the Modified Maekawa model this array contains four values [§10]:

usrval(1)

is the compressive strength.

usrval(2)

is the tensile strength.

usrval(3)

is the fracture energy.

usrval(4)

is the correction factor for plastic evolution.

These variables shall not be updated in this subroutine!

usrsta

are the user-supplied state variables. For the Modified Maekawa model this array contains 56 values [§10]:

usrsta(1)

is the fracture parameter K which gradually reduces to zero with ongoing deformation.

usrsta(2-56)

is workspace.

usrind

are the user-supplied integer indicator variables. For the Modified Maekawa model this array contains five values [§10]:

usrind(1)

indicates the softening model.

usrind(2)

indicates the crack model.

usrind(3-5)

is workspace.

sig

is the total stress vector [Table 11.1], it comes in from the final iteration of the previous step and must go out for the current iteration.

stiff

is the tangent stiffness matrix, it comes in from the previous step and must go out for the current iteration.