*HEADING
 NAFEMS BENCHMARK EXAMPLE 3DNLG-3  ELEMENT:B31
 ELASTIC LATERAL BUCKLING OF A RIGHT ANGLE FRAME UNDER IN-PLANE END MOMENTS
 APPLY PERTURBATION LOAD AND SLIGHT ROTATION
*NODE
1,-169.7056275,0.0
41,0.0,169.7056275,0.0
*NGEN
1,41
*ELEMENT,TYPE=B31
1,1,2
*ELGEN,ELSET=BEAM
1,40
*BEAM GENERAL SECTION,SECTION=RECT,ELSET=BEAM
0.6,30
0.0,0.0,-1.0
71240,27190.84
*AMPLITUDE,NAME=CONSTANT,TIME=STEP
0.0,1.0,1.0,1.0
*RESTART,WRITE
*STEP,NLGEOM,INC=10
put initial side load on frame
*STATIC
*BOUNDARY
41,XSYMM
1,2,5,0.0
*CLOAD
41,3,0.01
*CONTROLS, PARAMETERS=FIELD

,0.0,
*NSET,NSET=NOUT
1,41
*NSET,NSET=A
1,
*NSET,NSET=B
41,
*NODE FILE,NSET=NOUT
U, 
RF, 
*OUTPUT,FIELD
*NODE OUTPUT,NSET=NOUT
U,
RF,
*NODE PRINT,NSET=A,F=1
UR3,RM3
*NODE PRINT,NSET=B,F=1
U3, 
*END STEP
*STEP,NLGEOM,INC=45
get initial lateral buckling
*STATIC,RIKS
0.001,1.0,,,1.0
*MONITOR,NODE=1,DOF=6
*BOUNDARY,TYPE=VELOCITY,OP=NEW
1,2,5,0.0
1,6,6,0.08
41,XSYMM
*NODE PRINT,NSET=A,F=1
UR3,RM3
*NODE PRINT,NSET=B,F=1
U3, 
*NODE FILE,NSET=NOUT,FREQ=30
U, 
RF, 
*OUTPUT,FIELD,FREQ=30
*NODE OUTPUT,NSET=NOUT
U,
RF,
*END STEP