6.2.4 Compressive Behavior

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Subsections

6.2.4 Compressive Behavior

The compressive behavior of a Total Strain crack model is in general a nonlinear function between the stress and the strain in a certain direction. You may choose a predefined function [§6.2.4.1], or customize the compressive behavior via a user-supplied subroutine [§6.2.4.2]. See §18.2.7 for background theory.

6.2.4.1 Predefined Compression Functions

For a Total Strain crack model you can choose a predefined compression function by specifcation of the curve name and appropriate parameters.

(syntax)

$\begin{figure}\centering \begin{tabbing} \texttt{'MATERI'} \\ [-1.0ex] \rule{14... ...s\;\)\hspace{14ex}\=\emph{compression parameters} {]} \end{tabbing} \end{figure}$

COMCRV

curve is the name of the compression function which models the crushing behavior of concrete [Fig.6.6]. [ELASTI]

**Figure 6.6:** Predefined compression behavior for Total Strain model
$\begin{figure} \setlength{\unitlength}{1cm} \begin{footnotesize} \begin{picture... ...enterline{\raise 6.5cm\box\graph} } \end{picture}\end{footnotesize} \end{figure}$

Compression parameters.

If you specified the basic properties via a Model Code [§6.2.1.1], then DIANA can determine all compression parameters without further input. Else you must specify the compression parameters, depending on the compression function, as outlined in the following.

Elastic (syntax)

$\begin{figure}\centering \begin{tabbing} \texttt{'MATERI'} \\ [-1.0ex] \rule{14... ...\tiny {80}}}\\ * \>\>\texttt{COMCRV}\>\texttt{ELASTI} \end{tabbing} \end{figure}$

ELASTI: for elastic behavior in compression [Fig.6.6a]. Elastic behavior needs no further input parameters.

Ideal and Thorenfeldt (syntax)

$\begin{figure}\centering \begin{tabbing} \texttt{'MATERI'} \\ [-1.0ex] \rule{14... ...\>\texttt{USRCST}\>\texttt{\textit{usrkey}}$_{w}\,$ \end{tabbing} \end{figure}$

CONSTA: for a constant diagram [Fig.6.6b].
THOREN: for the function of Thorenfeldt at al. [Fig.6.6c]. The parameters of the Thorenfeldt curve (18.96) are unit-dependent. To calculate these parameters, DIANA assumes by default that the input data is in SI-units.
If you describe the finite element model in units other than SI, then you must explicitly specify the units that you used in input table 'UNITS' [Vol. Analysis Procedures].
COMSTR: fc is the compressive strength f_c .
TEM $\sqcup$ $\sqcup$ $\sqcup$: influence by temperature: a1 to an are tempreatures T . The temperature-time dependency must be specified via input table 'TEMPER' [§1.2.1].
CON $\sqcup$ $\sqcup$ $\sqcup$: influence by concentration: a1 to an are concentrations C . The concentration-time dependency must be specified via input table 'CONCEN' [§1.2.2].
MAT $\sqcup$ $\sqcup$ $\sqcup$: influence by maturity: a1 to an are maturity variables M . The maturity-time dependency must be specified via input table 'MATURI' [§1.2.3].
PRE $\sqcup$ $\sqcup$ $\sqcup$: influence by pressure: a1 to an are pressures P . The pressure-time dependency must be specified via input table 'PRESSU' [§1.2.4].
$\sqcup$ $\sqcup$ $\sqcup$ CST: influence on the compressive strength: fc1 to fcn are the f_c values for the ambient values a1 to an.
USRCST: compressive strength determined via subroutine USRCST [§11.3.9].

Linear hardening (syntax)

$\begin{figure}\centering \begin{tabbing} \texttt{'MATERI'} \\ [-1.0ex] \rule{14... ...\>\texttt{USRCST}\>\texttt{\textit{usrkey}}$_{w}\,$ \end{tabbing} \end{figure}$

LINHAR: for a linear hardening diagram [Fig.6.6d].
COMSTR: fc is the compressive strength f_c .
EHAR: ehar is the hardening modulus E_har .
TEM $\sqcup$ $\sqcup$ $\sqcup$: influence by temperature: a1 to an are tempreatures T . The temperature-time dependency must be specified via input table 'TEMPER' [§1.2.1].
CON $\sqcup$ $\sqcup$ $\sqcup$: influence by concentration: a1 to an are concentrations C . The concentration-time dependency must be specified via input table 'CONCEN' [§1.2.2].
MAT $\sqcup$ $\sqcup$ $\sqcup$: influence by maturity: a1 to an are maturity variables M . The maturity-time dependency must be specified via input table 'MATURI' [§1.2.3].
PRE $\sqcup$ $\sqcup$ $\sqcup$: influence by pressure: a1 to an are pressures P . The pressure-time dependency must be specified via input table 'PRESSU' [§1.2.4].
$\sqcup$ $\sqcup$ $\sqcup$ CST: influence on the compressive strength: fc1 to fcn are the f_c values for the ambient values a1 to an.
USRCST: compressive strength determined via subroutine USRCST [§11.3.9].

Multi-linear (syntax)

$\begin{figure}\centering \begin{tabbing} \texttt{'MATERI'} \\ [-1.0ex] \rule{14... ...xtit{sn}}$_{r}\,$ \texttt{\textit{en}}$_{r}\,${]} \end{tabbing} \end{figure}$

A multi-linear diagram fully describes the relationship between the compressive stress and the equivalent strain, therefore input of the compressive strength f_c is not necessary.

MULTLN: for a multi-linear diagram [Fig.6.6e].
COMPAR: are the points of the multi-linear diagram: n pairs of values ( $\sigma$ , $\varepsilon$ ); ( 1 $\leq$ n $\leq$ 30 )s0 to sn are the compression stresses $\sigma$ , e0 to en are the corresponding total strains $\varepsilon$ . Note that you should enter stresses rather than strengths. Following the standard sign convention of DIANA, compressive stresses and compressive strains should be input as negative.

(file.dat)

'MATERI
   1 YOUNG   3.0D+10
     TOTCRK  ROTATE
     TENCRV  HORDYK
     TENSTR  3.0D+06
     GF1     600.0
     COMCRV  MULTLN
     COMPAR  0.0D+00  0.0D+00
             -30.0D+06 -1.0D-03
             -60.0D+06 -1.0D+00

Saturation type (syntax)

$\begin{figure}\centering \begin{tabbing} \texttt{'MATERI'} \\ [-1.0ex] \rule{14... ...\>\texttt{USRCST}\>\texttt{\textit{usrkey}}$_{w}\,$ \end{tabbing} \end{figure}$

SATURA: for saturation type hardening [Fig.6.6f].
COMSTR: fc0 is the initial compressive strength f_c₀ .
COMSTO: fcinf is the ultimate compressive strength f_c at infinite strain.
EHAR: which defines the constant hardening modulus E_har .
GAMMA: gam is the decaying factor $\gamma$ .
TEM $\sqcup$ $\sqcup$ $\sqcup$: influence by temperature: a1 to an are tempreatures T . The temperature-time dependency must be specified via input table 'TEMPER' [§1.2.1].
CON $\sqcup$ $\sqcup$ $\sqcup$: influence by concentration: a1 to an are concentrations C . The concentration-time dependency must be specified via input table 'CONCEN' [§1.2.2].
MAT $\sqcup$ $\sqcup$ $\sqcup$: influence by maturity: a1 to an are maturity variables M . The maturity-time dependency must be specified via input table 'MATURI' [§1.2.3].
PRE $\sqcup$ $\sqcup$ $\sqcup$: influence by pressure: a1 to an are pressures P . The pressure-time dependency must be specified via input table 'PRESSU' [§1.2.4].
$\sqcup$ $\sqcup$ $\sqcup$ CST: influence on the initial compressive strength: fc01 to fc0n are the f_c₀ values for the ambient values a1 to an.
USRCST: initial compressive strength determined via subroutine USRCST [§11.3.9].

Parabolic (syntax)

$\begin{figure}\centering \begin{tabbing} \texttt{'MATERI'} \\ [-1.0ex] \rule{14... ...\>\texttt{USRCST}\>\texttt{\textit{usrkey}}$_{w}\,$ \end{tabbing} \end{figure}$

PARABO: for a parabolic diagram [Fig.6.6g]. The parabolic curve is based on fracture energy by the definition of the crack bandwidth of the element, for which DIANA assumes a value h related to the square root of the area of the element. In special cases, it may be useful to specify the crack bandwidth explicitly via the CRACKB input data item [§6.3].
COMSTR: fc is the compressive strength f_c .
GC: gc is the compressive fracture energy G_c .
TEM $\sqcup$ $\sqcup$ $\sqcup$: influence by temperature: a1 to an are tempreatures T . The temperature-time dependency must be specified via input table 'TEMPER' [§1.2.1].
CON $\sqcup$ $\sqcup$ $\sqcup$: influence by concentration: a1 to an are concentrations C . The concentration-time dependency must be specified via input table 'CONCEN' [§1.2.2].
MAT $\sqcup$ $\sqcup$ $\sqcup$: influence by maturity: a1 to an are maturity variables M . The maturity-time dependency must be specified via input table 'MATURI' [§1.2.3].
PRE $\sqcup$ $\sqcup$ $\sqcup$: influence by pressure: a1 to an are pressures P . The pressure-time dependency must be specified via input table 'PRESSU' [§1.2.4].
$\sqcup$ $\sqcup$ $\sqcup$ CST: influence on the compressive strength: fc1 to fcn are the f_c values for the ambient values a1 to an.
USRCST: compressive strength determined via subroutine USRCST [§11.3.9].

6.2.4.2 User-supplied Compression

DIANA offers the user-supplied subroutine mechanism for cases where the hardening or the ambient influence on the compressive stress cannot be input by one of the predefined curves as described. The compressive stress can be a function of an internal parameter, temperature, concentration, maturity and time.

(syntax)

$\begin{figure}\centering \begin{tabbing} \texttt{'MATERI'} \\ [-1.0ex] \rule{14... ...{USRPAR}\>\texttt{\textit{usrpar}}$_{r\ldots}\,${]} \end{tabbing} \end{figure}$

USRCRV: specifies that the function of the compressive stress is determined via user-supplied subroutine USRCRV [§11.3.1].
USRPAR: usrpar is a series of parameters of the user-supplied curve which DIANA passes to the subroutine.

Next: 6.2.5 Lateral Influence Up: 6.2 Total Strain Crack Previous: 6.2.3 Shear Behavior Contents Index

DIANA-9.3 User's Manual - Material Library
First ed.

Copyright (c) 2008 by TNO DIANA BV.