GROUNDCHECK

Subcase Information Entry

GROUNDCHECK – Rigid Body Motion Grounding Check

Description

The GROUNDCHECK command can be used in the Subcase Information section to perform a grounding check analysis on the stiffness matrix to expose unintentional constraints by moving the model rigidly.

Format

GROUNDCHECK(print,GRID=gid,THRESH=thresh) = option

Argument	Options	Description
print	< PRINT, NOPRINT > Default = PRINT	PRINT:	Write output to the .out file.
		NOPRINT:	Do not write output to the .out file.

grid	< GID > Default = geometric center of the structure.	Grid Point ID: Reference grid point for the calculation of the rigid body motion.

thresh	< e > Default = largest term in the stiffness matrix, divided by 1.0E10.	Maximum strain energy which passes the check.

option	< YES, NO > Default = YES	YES:	Grounding check is performed.
		NO:	Grounding check is not performed.

Comments

1.	GROUNDCHECK must be specified before the first SUBCASE.

2.	Grounding check is performed on all degrees-of-freedom of the model and all degrees-of-freedom that are not constrained by SPC. MPC equations are not used in the check.

3.	Any MPC that will be violated due to rigid body modes is reported. An equivalent energy magnitude is also calculated between MPC violation and the strain energy. The equivalent energy from MPC violation is added to the strain energy when performing the grounding check.