Define General Spring Type

Define the values of general spring support with 6x6 coupled matrix for stiffness, damping and mass.

From the Main Menu select Boundary > Spring Supports > Define General Spring Type.

Name
Enter the name of general nodal spring stiffness.

Input Method

Stiffness Matrix

Mass Matrix: Check on to enter the mass matrix.

Damping Matrix: Check on to enter the damping matrix.

Coupled Spring Stiffness
Enter the general nodal spring stiffness.

SDx-SDx
Spring stiffness in x-direction of GCS or node's local coordinate system (when node's local coordinate system is declared)

SDx-SDy
Spring stiffness related to x- and y-direction of GCS or node's local coordinate system (when node's local coordinate system is declared)

SRz-SRz
Rotational spring stiffness about z-direction of GCS or node's local coordinate system (when node's local coordinate system is declared)

Note
General spring is normally used to reflect the support stiffness of piles. Pile support stiffness related to each degree-of-freedom are considered in the structural analysis.

In typical building structures, analysis models do not include the pile footings. Instead, boundary springs are assumed to exist at the bottom of foundation or at the pile caps. The following general stiffness offers true stiffness of pile elements. For batter piles, use Node's local Axis to calculate the stiffness in the skewed directions.

Composition of general spring stiffness

* Assumptions

Modulus of elasticity: E

Section's moments of inertia: Iy, Iz

Cross sectional area: A

Length: L

(Shear deformation not considered)