Link Properties

A link is unlike other elements in that it does not have stiffness, instead it created a constraint condition between the two ends of the element. The behaviour of a link element is like a rigid constraint with just two nodes. Degrees of freedom that are not linked have no connection at all.

Definition

Name

The name is only used as a convenient way of identifying a link property.

Type of Linkage

The type should be set to “All” to make a link completely rigid. There are however many cases in which it is useful to make a link rigid in a plane (for example in modelling floor slabs). The following planes can be specified:

Linked Degrees of Freedom:

Linkage	DOF x	DOF y	DOF z	DOF xx	DOF yy	DOF zz
All	x	y	z	xx	yy	zz
All (pin)	x	y	z
xy plane	x	y				zz
yz plane		y	z	xx
zx plane	x		z		yy
xy plane (pin)	x	y
yz plane (pin)		y	z
zx plane (pin)	x		z

The “pin” linkage types do not include the rotational degrees of freedom at the constrained node in the rigid body displacements. Note that the “pin” condition applies only to the constrained node - the rotational degrees of freedom at the primary are always retained.

The above options can be used in both the Gss and GsRelax solvers. A further set of Links are available for use only in the GsRelax solver; see GsRelax modelling implications for more details:

• Tension – the link supports tension only
• Compression – the link supports compression only
• Bar – the link works in both tension and compression

There is also a general Link type, though it is not available for use in all solvers:

• Custom – the link works like a joint linking the nodes in the specified coupled directions

Constraints

More details are given in Link elements and rigid constraints. Care should be taken to avoid conflicting constraints.

Note about the property axis

The nodal constraint axis of the first topology (primary) node of the element is used as the link property axis.