2.2 Availability for Elements

This section outlines the availability of material models for the various element families for structural analysis. See Volume Element Library for description of basic variables and input of these elements. Table 2.1 presents an overview.

Table 2.1: MATERIAL MODELS FOR STRUCTURAL ANALYSIS

	truss	beam	pl. stress	plate bend.	pl. strain	axisymm.	fl. shell	cu. shell	solid	reinfo.
Linear elasticity	a	a	a	a	a	a	a	a	a	a
Nonlinear elasticity	a	b	c	-	c	e	-	a	c	-
Modified elasticity	a	b	c	-	c	e	-	a	c	-
Plasticity	e	bf	c	-	c	e	g	a	c	a
Orthotropic plasticity	-	-	c	-	c	e	-	a	c	-
Viscoplasticity	a	b	c	-	c	e	-	a	c	a
Cracking	a	b	c	-	c	e	-	a	c	-
Viscoelasticity	a	b	c	-	c	e	-	a	c	-
Creep	a	b	c	-	c	e	-	a	c	-
Shrinkage	a	b	c	-	c	e	-	a	c	-
Soil specials	-	-	a	-	a	a	-	-	c	-
Crack, total strain	a	b	a	-	e	e	-	a	c	-
Hyperelasticity	-	-	-	-	d	d	-	-	d	-
User-supplied subr.	a	b	c	-	c	e	-	a	c	-

(a) All elements. (b) Not for class-I. (c) For regular elements only. (d) For rubber elements only. (e) Not for rubber elements. (f) Only Tresca, Von Mises, Mohr-Coulomb, and Drucker-Prager. (g) Only for spline elements. (-) Not applicable.

The details are outlined in the following.

Combination of material models.

Generally speaking, DIANA can handle physically realistic combinations of the various material models. However, there are a few exceptions to this general rule.

The following combinations of material models result in erroneous, or preliminary terminated, nonlinear analysis.

• Nonlinear elasticity and plasticity.
• Nonlinear elasticity and cracking. In particular the material models for soil, such as Cam-clay [§5.1.4] and Modified Mohr-Coulomb [§5.1.5], cannot be combined with cracking because these plasticity models also include nonlinear elasticity.
• Nonlinear elasticity and viscoelasticity.
• Viscoelasticity and plasticity.

Furthermore, combination of different models for the same phenomenon in one element may lead to erroneous results or preliminary terminated analysis. For instance Rankine type plasticity [§5.1.3] may not be combined with Smeared cracking [§6.1] because either one models the cracking in the tensile regime.

Ambient influence.

Temperature, concentration and maturity may have influence on the various material models. Table 2.2 shows for the various element families which of the tree phenomena may influence the material properties.

Table 2.2: AMBIENT INFLUENCE ON MATERIAL MODELS

	truss	beam	pl. stress	plate bend.	pl. strain	axisymm.	fl. shell	cu. shell	solid	reinfo.
Temperature	a	a	c	-	c	e	-	a	c	a
Concentration	a	a	c	-	c	e	-	a	c	-
Maturity	a	b	c	-	c	e	-	a	c	-

(a) All elements. (b) Not for class-I. (c) For regular elements only. (e) Not for rubber elements. (-) Not applicable.

Truss elements.

The concrete [§5.1.3], Egg Cam-clay [§5.1.4], and Modified Mohr-Coulomb [§5.1.5] plasticity models cannot be used for truss elements.

Beam elements.

Nonlinear material models cannot be used for the class-I beam elements. Therefore these elements are not suited for physical nonlinear analysis. The concrete [§5.1.3], Egg Cam-clay [§5.1.4], and Modified Mohr-Coulomb [§5.1.5] plasticity models cannot be used for beam elements.

Plane stress elements.

The elements with drilling rotation can only be applied with linear elastic material properties. The elements with orthotropic thickness cannot be used in nonlinear analysis. The wrinkling element T9WME can only be applied with linear elastic material properties.

Plane strain elements.

For the rubber elements, the only material model available is hyperelasticity.

Axisymmetric elements.

For the rubber elements, the only material model available is hyperelasticity.

Plate bending elements.

The plate bending elements do not support any of the nonlinear material models. In nonlinear analysis these elements can only have linear elastic material.

Flat shell elements.

Neither the regular flat shell elements nor the flat shell elements with drilling rotation do support any of the nonlinear material models. In nonlinear analysis these elements can only have linear elastic material. Spline elements allow a plasticity model in nonlinear analysis.

Curved shell elements.

The concrete [§5.1.3], Egg Cam-clay [§5.1.4], and Modified Mohr-Coulomb [§5.1.5] plasticity models cannot be used for curved shell elements.

Solid elements.

The regular solid elements support all nonlinear analysis options. For the rubber elements, the only material model available is hyperelasticity. The concrete plasticity models [§5.1.3] cannot be used for solid elements.

Structural interface elements.

The structural interface elements do not support ambient influence on material properties. Crack dilatancy is only supported for the two-dimensional interface elements. See §9.3 for description of input syntax.

Spring elements.

The translation and torsion spring elements support an linear and nonlinear elastic model and a plasticity model [§9.1].

Reinforcement options.

The embedded BAR and GRID reinforcements support linear elasticity, plasticity and temperature influence. See §9.5 for description of input syntax.