/PROP/TYPE28 (NSTRAND)

Block Format Keyword Describes the multi-strand property set.

Format

(1)	(2)	(3)	(5)	(7)	(9)
/PROP/TYPE28/`prop_ID`/`unit_ID` or /PROP/NSTRAND/`prop_ID`/`unit_ID`
`prop_title`
`Mass`		`K`	`C`
`fct_ID`₁	`fct_ID`₂	$ε_{\min}$	$ε_{\max}$	`Y_SCAL`	`X_SCAL`
$μ_{i}$		$μ_{2}$

Specific friction coefficient for pulleys or strands 9 10

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
`Type`	`k`	$μ$

Field	Contents	SI Unit Example
`prop_ID`	Property identifier (Integer, maximum 10 digits)
`unit_ID`	Unit Identifier (Integer, maximum 10 digits)
`prop_title`	Property title (Character, maximum 100 characters)
`Mass`	Mass per unit length (Real)	$[\frac{kg}{m}]$
`K`	Stiffness for a length of a unitary length (Real)	$[N]$
`C`	Damping coefficient of a unitary length (Real)	$[Ns]$
`fct_ID`₁	Function identifier defining $F = f (ε)$ (Integer)
`fct_ID`₂	Function identifier defining $G = f (\dot{ε})$ (Integer)
$ε_{\min}$	Compression failure strain Default = -10³⁰ (Real)
$ε_{\max}$	Tension failure strain Default = 10³⁰ (Real)
`Y_SCAL`	Coefficient for the force (homogeneous to a force) Default = 1.0 (Real)	$[N]$
`X_SCAL`	Coefficient for the strain rate (homogeneous to a force) Default = 1.0 (Real)	$[\frac{1}{s}]$
$μ_{1}$	Pulley general friction coefficient (Real)
$μ_{2}$	Strand general friction coefficient (Real)
`Type`	Keyword "PULLEY" or "STRAND" (left justified) (Character)
`k`	Pulley or strand number (internal node number in the element) (Integer)
$μ$	Friction coefficient at pulley or along strand (Real)

To define the connectivity of multi-strand elements, refer to /XELEM.
The force in the spring is computed as:
Linear spring:(1)
$F = \frac{K}{L_{0}} δ + \frac{C}{L_{0}} \dot{δ}$

Nonlinear spring:(2)
$F = f (ε) \cdot g (\dot{ε}) + \frac{C}{L_{0}} \dot{δ}$

if $fct_I D_{1} \neq 0$ or $fct_I D_{2} \neq 0$

Where, $\dot{ε}$ is the engineering strain:(3)
$ε = \frac{δ l}{L_{0}}$

and $L_{0}$ is the reference length of element.
If $fct_I D_{1} = 0$ ,(4)
$F = g (\dot{ε}) + \frac{C}{L_{0}} \dot{δ}$
If $fct_I D_{2} = 0$ ,(5)
$F = f (ε) + \frac{C}{L_{0}} \dot{δ}$
Pulley type friction is defined (except at end nodes of the element).

Figure 1.
(6)
$| F_{k - 1} - F_{k} | \leq (F_{k - 1} + F_{k}) \tanh (\frac{β μ}{2})$
$F_{k - 1}$ is the force in strand connecting nodes N_k-1 and N_k.
F_k is the force in strand connecting nodes N_k and N_k+1.
You can also define friction along strands.
Specific friction coefficients is defined (different from general values) for some pulleys or for some strands (Line 6).
If n is the total number of nodes of an element, strands are numbered from one to (n) and all pulleys (internal nodes) are numbered from 2 to (n-1).