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CONNECTOR_SPRING

Connectors

*CONNECTOR_SPRING
coid, N${}_1$, N${}_2$, $m$, $k$, $\xi$, $F_{fail}$, direc, $l_0$

Parameter definition

Variable
Description
coid
Spring connector ID
N${}_1$
Node 1
N${}_2$
Node 2
$m$
Mass
quantity: Mass
$k$
Stiffness (force per unit distance of elongation) or a FUNCTION defining the elastic force versus elongation
quantity: Stiffness
$\xi$
Fraction of critical damping or a FUNCTION defining the damping force versus elongation rate
$F_{fail}$
Spring failure force
quantity: Force
default: No failure
direc
Spring force direction
options:
0 $\rightarrow$ tension and compression
1 $\rightarrow$ tension only
2 $\rightarrow$ compression only
$l_0$
Unloaded spring length
quantity: Length
default: Same as initial spring length

Description

This command defines a two-node spring connector with lumped mass and optional damping and failure.

The elastic and damping behavior can be given either as constants or through referenced FUNCTIONs, allowing both linear and nonlinear force laws. Parameter direc limits the response to tension, compression or both.

If $l_0$ is omitted, the initial distance between the two nodes is taken as the unloaded spring length.

Example

Linear spring connector

A linear spring with ID 5 connecting node 41 with node 42.

*PARAMETER m = 0.01 k = 1.0e2 xi = 0.1 *CONNECTOR_SPRING 5, 41, 42, [%m], [%k], [%xi]
Non-linear spring connector

A spring with ID 10 connecting node 43 with node 44. Functions are used to define the elastic force versus elongation (dnorm) and the damping force versus rate of elongation (vnorm). Note that dnorm and vnorm are built in variables.

*PARAMETER m = 0.01 k0 = 1.0e2 k1 = 1.0e3 c0 = 20.0 c1 = 5.0 *CONNECTOR_SPRING 10, 43, 44, [%m], fcn(10), fcn(20) # # Elastic force versus elongation *FUNCTION 10 %k0*dnorm + %k1*dnorm^2 # # Damping force versus elongation rate *FUNCTION 20 %c0*(exp(%c1*vnorm)-1)