# CELAS2

Bulk Data Entry Defines a scalar spring element of the structural model without reference to a property entry.

## Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
CELAS2 EID K G1 C1 G2 C2 GE S

## Example

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
CELAS2 28 6.2+3     19 4

## Definitions

Field Contents SI Unit Example
EID Unique element identification number.

No default (Integer > 0)

K Spring stiffness.

No default (Real)

G1, G2 Geometric grid point or scalar point identification number.

Default = 0 (Integer ≥ 0)

C1, C2 Component number in the displacement coordinate system specified by the CD entry of the GRID data.

Default = 0 (0 ≤ Integer ≤ 6)

GE Damping coefficient.

GE is ignored in Transient Analysis, if PARAM, W4 is not specified.

Default = 0.0 (Real)

S Stress coefficient.

Default = 0.0 (Real)

1. Zero or blank may be used to indicate a grounded terminal G1 or G2 with a corresponding blank or zero C1 or C2. A grounded terminal is a point whose displacement is constrained to zero.
2. Scalar points may be used for G1 and/or G2 (with a corresponding C1 and/or C2 of zero or blank). If only scalar points and/or grounded terminals are involved, it is more efficient to use the CELAS4 entry.
3. This single entry completely defines the element since no material or geometric properties are required.
4. The two connection points (G1, C1) and (G2, C2) must be distinct.
5. To obtain the damping coefficient GE, multiply the critical damping ratio, $C/{C}_{0}$ by 2.
6. A scalar point specified on this entry does not need to be defined on a SPOINT Bulk Data Entry.
7. The element force of a spring is calculated from the equation:(1)
$f=k*\left({u}_{1}-{u}_{2}\right)$
Where, $k$ is the stiffness coefficient for the scalar element, ${u}_{1}$ is the displacement of the first degree-of-freedom listed on the CELAS1 and CELAS2 entries and ${u}_{2}$ is the displacement of the second degree-of-freedom listed on the CELAS1 and CELAS2 entries.
Element stresses are calculated from the equation:(2)
$s=S*f$
Where, $S$ is the stress coefficient as defined above.
8. When the SPSYNTAX setting on the SYSSETTING I/O Options Entry is set to CHECK (default) or STRICT, it is required for grid/component pairs (G#/C#) that the component be 0 or blank when the grid reference is a scalar point (SPOINT), and that the component be > 1 when the grid reference is a structural grid point (GRID). When SPSYNTAX is set to MIXED, it is allowed for grid/component pairs (G#/C#) that the grid reference be either a scalar point (SPOINT) or a structural grid point (GRID) when the component is 0, 1 or blank; interpreting all of these as 0 for scalar points and as 1 for structural grids. When the component is greater than 1, the grid reference must always be a structural grid (GRID).
9. A CBUSH element, referencing a PBUSH property with a single stiffness term, is equivalent to a CELAS1 or CELAS2 element, only when the elements have zero length. A non-zero length CBUSH assumes rigid body connections from the connection points, GA and GB, to the spring-damper location, as defined either by S or the OCID and Si fields.
10. This card is represented as a spring or mass element in HyperMesh.