help regarding amplitude in ABAQUS/standard

[pushkaraj123]

I have recently started using Abaqus...so my question might look obvious to some.Actually I am doing my preprocessing in I-DEAS and then exporting to the ABAQUS solver.MY model is rectangular concrete specimen.In the first step I apply two equal and opposite shear forces(concentrated loads) on both sides and in the 2nd step keeping the shear forces constant I apply a normal load upwards.But I,m having problems in applying the shear forces.I want to apply the forces such that they reach a particular value in 100 increments and that they should increase by the same value in each increment....but its not happening like that.One of the forces starts with a higher value than the other.I tried all types of amplitude definitions .
My question is why does the forces start form a value other than I prescribed inthe amplitude definition ?


Relevant part of my input file:



**% ====== AMPLITUDE DEFINITION ======
**%
*AMPLITUDE, NAME=AMPLITUDE_SETS_1, DEFINITION=TABULAR,
TIME=STEP TIME , VALUE=RELATIVE
0.000E+000, 0.000E+000, 1.000E-002, 1.000E+000, 2.000E-002, 2.000E+000, 3.000E-002, 3.000E+000
4.000E-002, 4.000E+000, 5.000E-002, 5.000E+000, 6.000E-002, 6.000E+000, 7.000E-002, 7.000E+000
8.000E-002, 8.000E+000, 9.000E-002, 9.000E+000, 1.000E-001, 1.000E+001, 1.100E-001, 1.100E+001
1.200E-001, 1.200E+001, 1.300E-001, 1.300E+001, 1.400E-001, 1.400E+001, 1.500E-001, 1.500E+001
1.600E-001, 1.600E+001, 1.700E-001, 1.700E+001, 1.800E-001, 1.800E+001, 1.900E-001, 1.900E+001
2.000E-001, 2.000E+001, 2.100E-001, 2.100E+001, 2.200E-001, 2.200E+001, 2.300E-001, 2.300E+001
2.400E-001, 2.400E+001, 2.500E-001, 2.500E+001, 2.600E-001, 2.600E+001, 2.700E-001, 2.700E+001
2.800E-001, 2.800E+001, 2.900E-001, 2.900E+001, 3.000E-001, 3.000E+001, 3.100E-001, 3.100E+001
3.200E-001, 3.200E+001, 3.300E-001, 3.300E+001, 3.400E-001, 3.400E+001, 3.500E-001, 3.500E+001
3.600E-001, 3.600E+001, 3.700E-001, 3.700E+001, 3.800E-001, 3.800E+001, 3.900E-001, 3.900E+001
4.000E-001, 4.000E+001, 4.100E-001, 4.100E+001, 4.200E-001, 4.200E+001, 4.300E-001, 4.300E+001
4.400E-001, 4.400E+001, 4.500E-001, 4.500E+001, 4.600E-001, 4.600E+001, 4.700E-001, 4.700E+001
4.800E-001, 4.800E+001, 4.900E-001, 4.900E+001, 5.000E-001, 5.000E+001, 5.100E-001, 5.100E+001
5.200E-001, 5.200E+001, 5.300E-001, 5.300E+001, 5.400E-001, 5.400E+001, 5.500E-001, 5.500E+001
5.600E-001, 5.600E+001, 5.700E-001, 5.700E+001, 5.800E-001, 5.800E+001, 5.900E-001, 5.900E+001
6.000E-001, 6.000E+001, 6.100E-001, 6.100E+001, 6.200E-001, 6.200E+001, 6.300E-001, 6.300E+001
6.400E-001, 6.400E+001, 6.500E-001, 6.500E+001, 6.600E-001, 6.600E+001, 6.700E-001, 6.700E+001
6.800E-001, 6.800E+001, 6.900E-001, 6.900E+001, 7.000E-001, 7.000E+001, 7.100E-001, 7.100E+001
7.200E-001, 7.200E+001, 7.300E-001, 7.300E+001, 7.400E-001, 7.400E+001, 7.500E-001, 7.500E+001
7.600E-001, 7.600E+001, 7.700E-001, 7.700E+001, 7.800E-001, 7.800E+001, 7.900E-001, 7.900E+001
8.000E-001, 8.000E+001, 8.100E-001, 8.100E+001, 8.200E-001, 8.200E+001, 8.300E-001, 8.300E+001
8.400E-001, 8.400E+001, 8.500E-001, 8.500E+001, 8.600E-001, 8.600E+001, 8.700E-001, 8.700E+001
8.800E-001, 8.800E+001, 8.900E-001, 8.900E+001, 9.000E-001, 9.000E+001, 9.100E-001, 9.100E+001
9.200E-001, 9.200E+001, 9.300E-001, 9.300E+001, 9.400E-001, 9.400E+001, 9.500E-001, 9.500E+001
9.600E-001, 9.600E+001, 9.700E-001, 9.700E+001, 9.800E-001, 9.800E+001, 9.900E-001, 9.900E+001
1.000E+000, 1.000E+002
**%
*PHYSICAL CONSTANTS,
STEFAN BOLTZMANN= 0.56696E-07,
ABSOLUTE ZERO=-0.27315E+03
**%
**%==========================================
**% HISTORY DATA
**%==========================================
**%
**% ====== STEP NUMBER 1 ======
**%
*STEP,NLGEOM,INC=150
*STATIC,DIRECT
.01,1
**% BOUNDARY CONDITION SET 1
**% RESTRAINT SET 1
*BOUNDARY,OP=NEW
BS000001, 1, 2, 0.00000E+00
**% LOAD SET 1
*CLOAD,OP=NEW,AMPLITUDE=AMPLITUDE_SETS_1
5434, 1,-1.0000E+05
5448, 1, 1.0000E+05
*NSET, NSET=BS000001, GENERATE
5428, 5429, 1
5433, 5441, 8
5456, 5459, 1
5498, 5526, 1
5588, 5591, 1
*NODE FILE,FREQUENCY=1,GLOBAL=YES
U
*OUTPUT, FIELD, FREQUENCY=1
*NODE OUTPUT, NSET=ALLNODES
U
*EL FILE, FREQUENCY=1, DIRECTIONS=YES
NFORC,
*OUTPUT, FIELD, FREQUENCY=1
*ELEMENT OUTPUT, ELSET=ALLELEMENTS
NFORC,
*END STEP

 

[xerf]

The value of the force at each time increment is force_value=Magnitude*Amplitude(time), if the amplitude curve si defined as relative (i.e. your case).

If you supply the amplitude curve by two points (at the inital and final time) it should be enough since Abaqus will interpolate linearly between the two amplitude points.