9.3.5 Combined Cracking-Shearing-Crushing

This interface material model is appropriate to simulate fracture, frictional slip as well as crushing along interfaces, for instance at joints in masonry. The model as a plasticity based multi-surface interface model and is also known as the `Composite Interface model'. See §21.5 for background theory.

    (syntax)

COMBIF

indicates the use of the multi-surface interface yield criterion for combined cracking-shearing-crushing.

GAPVAL

ft is the tensile strength f_t . ( 0$\le$f_t$\le$c/tan$\phi$ )Note that also the friction criterion limits tensile stresses. If you specify f_t > c/tan$\phi$ then DIANA will reset f_t to f_t = c/tan$\phi$ .

MO1VAL

gf1 is the fracture energy G_f^I ( G_f^I > 0 )for Mode-I.

FRCVAL

describes the friction criterion: ch is the cohesion c , (c > 0 )phi is the friction coefficient $\Phi$ , ($\Phi$ > 0 ) i.e., the tangent modulus of the friction angle $\phi$ ( $\Phi$ = tan$\phi$ ), psi is the dilatancy coefficient $\Psi$ ($\Psi$ > 0 )( $\Psi$ = tan$\psi$ ).

Non-consistent friction and dilatancy requires three more parameters: phir is the residual friction coefficient $\Phi_{{\mathrm{r}}}^{}$ , ( $\Phi_{{\mathrm{r}}}^{}$ > 0 )sigu is the confining normal stress $\sigma_{{\mathrm{u}}}^{}$ ( $\sigma_{{\mathrm{u}}}^{}$ < 0 )for which the dilatancy coefficient is zero, and delta is the exponential degradation coefficient $\delta$ ( $\delta$ > 0 )of the dilatancy coefficient with shear-slipping displacement [§21.5.1]. In this case the specified phi and psi will be considered as initial values.

MO2VAL

defines the Mode-II fracture energy G_f^II : gf2a and gf2b are the factors a and b (b > 0 )in G_f^II = a $\sigma$ + b . If you don't specify factor a this will be taken as zero by default, [a = 0 ] and G_f^II will be constant.

CAPVAL

describes the cap criterion: fc is the compressive strength f_c ( f_c > 0 )and cs is factor C_s ( C_s > 0 )which controls the shear traction contribution to compressive failure.

MOCVAL

describes the compressive inelastic law: gfc is the compressive fracture energy G_fc ( G_fc > 0 )and kp is the equivalent plastic relative displacement $\kappa_{{\mathrm{p}}}^{}$ ( $\kappa_{{\mathrm{p}}}^{}$ > 0 )corresponding to the peak compressive stress.