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 (45) 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 subincrements 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 arclength procedures 
If this value changes from zero to nonzero 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 arclength 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 