$ file autosup3.dat  inertia relief by rigid body modes 
diag 8
SOL 101
Include 'autosupa.v707' $
CEND
TITLE = inertia relief with r.b. modes constraints		autosup3
Subtitle = all basic coords, 6 rb modes from eigensoln., no s.e.s,  
Label = elevator descending with constant 0.5 g acceleration
Echo = both
DISPL=ALL
Oload = all
Elforce = all
Gpfo = all
Spcf = all
Load = 12
BEGIN BULK
param, inrel, -3 $ request autosuport using eigenmodes
$ elevator cage
$ top rail
CBAR,   12,      12,     1,      2,      ,       1.0   
$ I1 plane includes -2 direction
$ side rails
CBAR,   13       12      1       3,	,	1.0
Cbar,	24,	12,	2,	4,	,	1.0
$ floor
Cbar,	35,	12,	3,	5,	,	1.0
Cbar,	54	12,	5,	4,	,	1.0
PBAR,   12      21      1.0     2.0     1.0     1.25
$ tune so first mode about 0.1 hz.
MAT1,   21      1.0,	,	.3	1.0  
$	gid	cp	x	y	z	
GRID,	1,       , 	-1.,   	0.,	1.	
GRID,	2,       ,       +1.,	0.,	1.		
GRID,	3,       ,       -1.,	0.,	-1.	  
Grid,	4,	,	+1.,	,	-1.	 
Grid,	5,	,	0.	0.	-1. $ on centerline
$ payload at center of floor
CONM2,  5    	5,	,	10.0
grav,	1,	,	10.,	,	,	-1.
$ cable loads restraining gravity, about half of weight
force,	2	1,	,	45.	0.,	0.,	1.
force,	2	2,	,	45.	0.	0.	1.
Load,	12,	1.0	1.0	1	1.0	2 $ grav load
$ can not be in same set as other loads
$ optional inputs
param, grdpnt, 5 $ get weight summary.  optional
suport,	5	123456 $ at floor center.  Repeatable shape fcns.  optional
param, usetprt, 0 $ review user sets optional
ENDDATA

The elevator cage is a square, with a payload point at the center of the floor.  Cables are attached at each corner of the upper rail.  They are tuned to input a constant force equal to one half of the gravitational load while it descends.

This model uses Elbonian units of measure.  They believe strongly in unity, so all units of measure have a value of unity except the gravitational constant, which has the value of 10.0 whatevers per second per second.  Gravity is stronger than unity.  The whatever is the Elbonian measure of length.