Parameter Name |
Definition |
Description |
| MAR |
Maximum absolute residual |
See Convergence
Criteria |
| RMS |
Root mean square of the residuals |
See Convergence
Criteria |
| DPNRM |
Euclidean displacement norm as a percentage of the total
displacements |
See Convergence
Criteria |
| RDNRM |
Euclidean residual norm as a percentage of the total
reactions |
See Convergence
Criteria and Residual
Norm |
| WDNRM |
Work done by the residuals as a percentage of the work done
by the loads on iteration zero |
See Convergence
Criteria |
| DTNRM |
Euclidean displacement norm as a percentage of the total
displacements for the increment |
See Convergence
Criteria |
| EPSLN |
Reduction in energy in the current iterative direction
(used to trigger line searches) |
See Iterative
Acceleration |
| ETA |
Factor by which the iterative displacements are multiplied
by during a line search |
See Iterative
Acceleration |
| DELTL |
Incremental displacement length |
See Iterative
Acceleration |
| DELTW |
Incremental work done by the external loads |
- |
| DLMDA |
Change in load factor on the current iteration |
A check on the rate
of increase or decrease in the load increment for
automatic incrementation. A large value at iteration
zero followed by an unconverged increment can indicate
that the desired number of iterations is too large.
This parameter should decrease as the iterative
procedure continues in each increment. See nonlinear
load incrementation procedures |
| TLMDA |
Total load factor |
Monitors how much
load is currently applied for automatic incrementation
and also shows how much unloading is occurring due
to any step reduction. If the current number of
increments is large, tlmda is still low compared
to the final specified load factor and the number
of iterations per increment is low (4-5) then increase
the desired number of iterations and ensure no limit
on the load factor. See nonlinear
load incrementation procedures |
| LTDSP |
Value of the variable specified for the limiting
displacement |
See Termination
Criteria |
| MXSTP |
Maximum number of strain sub-increments used to return the
elastic predictor stress to the yield surface |
Values greater than zero indicate the occurrence of
plasticity in the solution. The greater the value, the more significant the effect of
plasticity in the solution. If it is zero and convergence is difficult, it will not be a
result of plasticity. If it is a large value it may cause automatic step reduction as a
result of internal divergence. If it is greater than zero on the first increment, it
usually indicates too large an initial load step or incorrect material definition. It is
not available for the concrete model Related Variable: PLWRK |
| NLSCH |
Number of line searches used on the current iteration |
The more line searches,
the greater the degree of nonlinearity occurring
in the current iteration. See nonlinear
iterative acceleration |
| CSTIF |
Current stiffness parameter |
See the current
stiffness parameter |
| PENMX |
Maximum penetration on slidelines |
A check for unreasonable penetration of a slideline
node. If the penetration exceeds reasonable values relative to the structure dimensions,
the slideline stiffness coefficients may need to be increased, conversely, reduced if
problems are being experienced and the penetration is relatively very small. If it
suddenly returns to zero during an analysis, contact has been lost (increase slideline
stiffness coefficients and/or mesh density). If it has been zero from the beginning of the
analysis, contact has not been established Related Variable: NDPMX |
| NDPMX |
Slideline node at which maximum penetration occurs |
Related Variable: PENMX |
| KDSMX |
Node:Variable number at which maximum incremental
displacement occurs |
Investigation of the mesh in the area surrounding this
node may indicate the cause of any pivot problems reported in the LUSAS output file. |
| ISURF |
A switch to control whether the load level is to be
controlled by constant or arc-length procedures |
If this value changes from zero to non-zero during the
solution, a significant degree of softening behaviour has occurred in the structure. If
only material or boundary condition nonlinearity id specified, change the threshold at
which arc-length procedures are automatically invoked to zero - this would also be the
case for geometrically nonlinear analysis in which buckling is not expected.
See Constrained
Solution Methods
|
| ENGY |
Total strain energy |
The current total elastic strain energy in the structure
as a result of the loading |
| PLWRK |
Total plastic work |
The current total plastic strain energy in the structure
as a result of the loading |
| PIVMN |
Minimum pivot value from tangent stiffness |
Except for buckling analyses, this value should always
be positive.
Further details for negative,
zero
or small
pivot values as well as a checklist
of pivot problem remedies are available.
|
| PIVMX |
Maximum pivot value from tangent stiffness |
Numerical difficulties will be experienced as this value
approaches the maximum real number that the computer operating system can handle
For very large pivot values, see diagonal
decay information.
|
| NSCH |
Number of negative pivots found during solution |
Should always be zero unless a nonlinear buckling
analysis is being performed. Related Variable: PIVMN |
| KPVMN |
Node:Variable number at which minimum pivot occurs |
Investigation of the mesh in the area surrounding this
node may indicate the cause of any pivot problems reported in the LUSAS output file. Related
Variable: PIVMN |
| KPVMX |
Node:Variable number at which maximum pivot occurs |
Investigation of the mesh in the area surrounding this
node may indicate the cause of excessively large pivot values. Related Variable: PIVMN |
