Applies To
	Product(s):	STAAD.Pro
	Version(s):	All
	Environment:	N/A
	Area:	Modeling Solutions
	Subarea:	Supports
	Original Author:	Bentley Technical Support Group

When using the foundation support, I am required to give the subgrade modulus and supply a direction. I have always used Y as the direction. However, I am interested in knowing what would occur if I choose Y-only. Is there some type of weak spring placed in X & Z directions, is it completely restrained, or is it somewhere in between?

If X or Y or Z is specified for direction, then,

a) a spring support is generated in that direction 
b) the other two translational directions are fully restrained
c) the associated rotational degre of freedom is fully restrained
d) the other 2 rotational degrees of freedom are treated as unrestrained

Example :

plate-list PLATE MAT DIR Y SUBGRADE 0.4

FX is fixed
FY gets a spring
FZ is fixed
MX is free
MY is fixed
MZ is free

If XONLY or YONLY or ZONLY is specified, then, a spring support is generated in that direction. All the remaining 5 degrees of freedom are treated as unrestrained.

Example :

plate-list PLATE MAT DIR YONLY SUBGRADE 0.4

FX is free
FY gets a spring
FZ is free
MX is free
MY is free
MZ is free