10.4 Material Section

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Multiple material sections may be defined with an input file. Each material section is identified by its unique own name. A particular name must not be referenced by a solid section ($\rightarrow $10.6). In that case the respective material will be ignored.

The section keyword *MATERIAL has as option

*NAME=<name>

specifies a unique name which basically may be freely chosen (mandatory)



The section keyword *MATERIAL has own keywords.

A first keyword *DENSITY indicates the specific mass of the respective material. It has one dataline giving the value. Specific mass should not be confused with the specific weight, both differ by earth acceleration. The chosen mass unit has to be consistent with the units for length, force and time. If the keyword *DENSITY is not given a zero mass is assumed and dynamic calculations are performed as quasistatic.

Each material section or each section keyword *MATERIAL must have exactly one material keyword which currently has to be after the *DENSITY keyword ($\rightarrow $ open issue) within a material section. A material keyword denotes a material type. The following types are currently available:

material keyword

 

space

symmetric

book($\rightarrow $ http://www.concrete-fem.com)

   

dimensions

material matrix

sections

*ELASTIC

isotropic linear elastic

1D, 2D, 3D

yes

1.4, 5.3

*MISES

isotropic mises elasto-plastic

1D, 2D, 3D

yes

2.3, 5.5.1

*RCBEAM

plane reinforced concrete cross section

1D

 

3.1.3

*TCBEAM

plane reinforced concrete cross section

1D

 
 

completed with textile or other reinforcement

*ELASTICLT

isotropic linear elastic with limited tensile

1D, 2D

 

6.3

 

strength and smeared crack

*ELASTICLT_RCSHELL

*ELASTICLT adopted to shell layers

2D

 

8.7.1

*ISODAMAGE

isotropic damaged elasticity

1D, 2D, 3D

yes

5.6

*SPRING

nonlinear spring

1D

 

2.4

*MISESREMEM

*MISES adopted to reinforcement layers of plates

2D

 

6.4

*NLSLAB

nonlinear model for Kirchhoff slabs

2D

 

7.7



The following combinations between element types and material types are currently possible:

 

B23E

B23

B21E

B21

T1D2

T2D2

T3D2

S1D2

CPE3

CPE4

CPS3

CPS4

SB3

SH4

*ELASTIC

+

+

+

+

+

+

+

+

+

+

+

+

+

+

*MISES

+

+

+

+

+

+

+

-

+

+

+

+

-

+

*RCBEAM

+

+

+

+

-

-

-

-

-

-

-

-

-

-

*TCBEAM

+

+

+

+

-

-

-

-

-

-

-

-

-

-

*ELASTICLT

-

-

-

-

+

+

+

-

+

+

+

+

-

-

*ISODAMAGE

-

-

-

-

+

+

+

-

+

+

+

+

-

-

*SPRING

-

-

-

-

-

-

-

+

-

-

-

-

-

-

*MISESREMEM

-

-

-

-

-

-

-

-

+

+

+

+

-

-

*NLSLAB

-

-

-

-

-

-

-

-

-

-

-

-

+

-



Material keywords generally have no options. Each material keyword has its specific data line which are described in the following.

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10.4.1 Data of *ELASTIC

The data line describe the following properties

$E$,

$\nu $


with

$E$

Young’s modulus

$\nu $

Poisson’s ratio, not used for 1D



The given sequence is mandatory. Values have to be separated by commas. Extra values or comment like data are ignored. The same remarks hold for all data lines of the following material keywords.

10.4.2 Data of *MISES

The data line describe the following properties

$E$,

$\nu $,

$f_ y$,

$f_ u$,

$\epsilon _ u$,

$\alpha _ T$


with

$E$

Young’s modulus

$\nu $

Poisson’s ratio, not used for 1D

$f_ y$

yield stress in case of uniaxial stress

$f_ u$

failure stress in case of uni axial stress

$\epsilon _ u$

strain corresponding to $f_ u$

$\alpha _ T$

thermal expansion coefficient

10.4.3 Data of *RCBEAM

The first data line describes the following concrete properties

$E_ c$,

$f_ c$,

$\epsilon _{c1}$,

$\epsilon _{cu1}$,

$f_{ct}$,

$n$

$\alpha _ T$

$\varphi $

$1/\zeta $


with

$E_ c$

Young’s modulus

$f_ c$

compressive strength

$\epsilon _{c1}$

strain corresponding to compressive strength

$\epsilon _{cu1}$

ultimate strainhardening strength in case of uniaxial stress

$f_{ct}$

tensile strength (used for tension stiffening)

$n$

number of layers for integration of nonlinear stress-strain relation

 

$n=1$ uses a linear relation without tension

 

$n=1$ is mandatory to compute creep of concrete

$\alpha _ T$

thermal expansion coefficient

$\varphi $

creep coefficient

$1/\zeta $

$\zeta \rightarrow $ creep time



The second data line describes the following reinforcing steel properties

$E$,

$\nu $,

$f_ y$,

$f_ u$,

$\epsilon _ u$,

$\alpha _ T$


with

$E_ s$

Young’s modulus

$\nu $

Poisson’s ratio, not used here for reinforcement

$f_ y$

yield strength in case of uniaxial stress

$f_ u$

hardening strength in case of uni axial stress

$\epsilon _ u$

strain corresponding to $f_ u$

$\alpha _ T$

thermal expansion coefficient


which corresponds to the *MISES data line.

10.4.4 Data of *TCBEAM

The first and second data line are the same as for the *RCBEAM material keyword.

The third dataline describes the following properties of a textile like brittle reinforcement

$E_0$,

$\epsilon _0$,

$f_ u$,

$\epsilon _ u$


with

$E_0$

compressive and initial tensile Young’s modulus

$\epsilon _0$

strain limiting upper range of $E_0$

$f_ u$

tensile strength

$\epsilon _ u$

strain corresponding to $f_ u$


which corresponds to a bilinear course with limited tensile strength.

10.4.5 Data of *ELASTICLT

The data line describe the following properties

$E$,

$\nu $,

$f_{ct}$,

$G_ f$,

$b_ w$,

$\varphi $,

$1/\zeta $,

$FC$

$\eta _ c$


with

$E$

Young’s modulus

$\nu $

Poisson’s ratio

$f_{ct}$

yield strength in case of uniaxial stress

$G_ f$

hardening strength in case of uniaxial stress

$b_ w$

strain corresponding to $f_ u$

$\varphi $

creep coefficient

$1/\zeta $

$\zeta \rightarrow $ creep time

$FC$

criterion for failure: $FC=0 \rightarrow $ stress, $FC=1 \rightarrow $ strain

$\eta _ c$

crack ‘viscosity’

10.4.6 Data of *ISODAMAGE

The data line describe the following properties

$E_0$,

$\nu $,

$f_ c$,

$f_{ct}$,

$LimTY$

$\alpha _{biax}$,

$r_{confined},$

$\alpha _{confined}$,

$RegTY$,

$R$,

$\eta _{artificial}$


with

$E_0$

initial Young’s modulus

$\nu $

Poisson’s ratio

$f_ c$

uniaxial compressive strength

$f_{ct}$

uniaxial tensile strength

$LimTy$

type of triaxial strength surface

 

choose $LimTy=1$

$\alpha _{biax}$

biaxal compressive strength related to uniaxial compressive strength

$r_{confined}$

circumferential stress related to longitudinal stress (compression) of confined cylinder specimen

$\alpha _{confined}$

longitudinal strength related uniaxial compressive strength of confined cylinder specimen

$RegTY$

regularization type

 

$RegTY=0$: no regularization

 

$RegTY=1$: gradient damage – might not work with all element types ($\rightarrow $ open issue)

 

$RegTY=2$: crack band – might not work with all element types ($\rightarrow $ open issue)

$R$

characteristic length for $RegTY=1$

 

cack energy for $RegTY=2$

$\eta _{artificial}$

artificial viscosity – sorry, this might sometimes be necessary for convergence (trial and error!)



Some care has to be taken in choosing the relations of $f_ c - E_0$, $f_ c - f_{ct}$, $r_{confined} - \alpha _{confined}$ and the value of $\alpha _{biax}$. There might be unfeasible choices. As an example

  36300.,0.2,   40.,3.5,  1,1.2,0.2,2.0,  2,150.e-6,  0.

should make sense for C40 according to MC2010.

10.4.7 Data of *SPRING

This material type provides a force $t$ depending on a relative displacement $s$. This is basically described by cubic splines. It behaves in the same way in the negative and positive range. The data line describes the following properties

$x$,

$s_1$,

$t_1$,

$s_2$,

$t_2$,

$s_0$,

$k_0$


with

$x$

currently not used

$s_1$

prescribed relative displacement

$t_1$

force prescribed with $s_1$

 

$\textrm{d}t/\textrm{d}s=0$ for $s=s_1$

$s_2$

prescribed relative displacement, $s_2>s_1$

$t_2$

force prescribed with $s_2$

 

$\textrm{d}t/\textrm{d}s=0$ for $s=s_2$

$s_0$

end of starting range of relative displacement with linear stiffness $k_0$ up to $s_0$

 

may be set to $s_0=0$ starting with a cubic spline with initial slope $k_0$

$k_0$

initial stiffness $\textrm{d}t/\textrm{d}s$ for $s=0$

10.4.8 Data of *MISESREMEM

This material type provides a reinforcement like plane sheet with uniaxial mises elasto-plasticity. The data line describes the following properties

$E$,

$\varphi $,

$f_ y$,

$f_ u$,

$\epsilon _ u$,

$\alpha _ T$


with

$E$

Young’s modulus

$\varphi $

orientation of reinforcement with respect to global $x$-direction in degrees

$f_ y$

yield strength in case of uniaxial stress

$f_ u$

hardening strength

$\epsilon _ u$

strain corresponding to $f_ u$

$\alpha _ T$

thermal expansion coefficient


which to a large degree corresponds to the *MISES data line.

10.4.9 Data of *NLSLAB

This material type provides a bilinear moment-curvature relation for usage with Kirchhoff-slabs. Elasto-plastic unloading is not covered. The data line describes the following properties

$k_ x$,

$k_ y$,

$m_ x$,

$m_ y$,

$k_{Tx}$,

$k_{Ty}$,

$\alpha $


with

$k_ x$

initial slab bending stiffness in global $x$-direction

$k_ y$

initial slab bending stiffness in global $y$-direction

$m_ x$

final slab moment of initial branch in global $x$-direction (‘yield’-moment)

$m_ y$

final slab moment of initial branch in global $y$-direction (‘yield’-moment)

$k_{Tx}$

final slab bending stiffness in global $x$-direction (‘hardening’-stiffness)

$k_{Ty}$

final slab bending stiffness in global $y$-direction (‘hardening’-stiffness)

$\alpha $

factor for twisting stiffness



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