Spring-damper element

*Connector element
<node set name 1>, <node set name 2>, <degree of freedom>, <stiffness> [, <viscous damping coefficient>]

With this option, a connector element between two node sets is generated (i.e. a spring-damper element). The entries of the <subsequent lines> are the name of the first node set <node set name 1>, the name of the second node set <node set name 2>, the <degree of freedom> (\({u_1,u_2,u_3}\)), the assigned stiffness of the connector element [F/A] and, potentially, a viscous damping coefficient [F*t/A] (unit of force times time divided by area). If only a dashpot element is to be considered, a stiffness of zero can be specified to deactivate the force resulting from the spring.

The difference between the *Equation commmand and the *Connector element definition is the possibility to define a specific stiffness (or damping) and obtain the connector force using the output variable CON_F (see *Output). The connector force is the sum of the forces resulting from the spring and the damper.

Only linear spring \(F^{spring} = stiffness \cdot (\boldsymbol{u}_1 - \boldsymbol{u}_2\)) and linear dampers are supported \(F^{damper} = damping coefficient \cdot (\boldsymbol{v}_1 - \boldsymbol{v}_2\)). \(\boldsymbol{u}_1\), \(\boldsymbol{u}_2\) are the displacements of the nodes between which the connector element is added and \(\boldsymbol{v}_1\), \(\boldsymbol{v}_2\) are their velocities.

The output variable CON_F is currently a scalar. If for one node two connector elements are defined, both are considered in the analysis but only the force of the second connector element is printed as output.