This option is used to define two coefficients used in the ISO equation, which predicts 
, the axial load at which the response switches to buckling only, for frame elements with buckling strut response. For a nondefault buckling envelope the *BUCKLING REDUCTION FACTORS option can be used only in conjunction with both the *FRAME SECTION, SECTION=PIPE, YIELD STRESS=
option and the *BUCKLING ENVELOPE option. For the default buckling envelope it can be used only in conjunction with the *FRAME SECTION, BUCKLING, SECTION=PIPE, YIELD STRESS= option.
Product: ABAQUS/Standard
Type: Model data
Level: Part Part Instance Model
Include this parameter to define the method for calculating the buckling reduction factor 
for bending about the first cross-section direction.
Set this parameter equal to TYPE1 (default) to set to the constant value of 
.
Set this parameter equal to TYPE2 for members with no distributed transverse loading. Then =max
, where 
is the ratio of smaller to larger moments about the first cross-section axis at the element ends.
Set this parameter equal to TYPE3 for members with distributed transverse loading. Then =min
, where 
is the compressive axial stress and 
is the Euler buckling stress corresponding to the first cross-section direction.
Include this parameter to define the method for calculating the buckling reduction factor 
for bending about the second cross-section direction.
Set this parameter equal to TYPE1 (default) to set to the constant value of .
Set this parameter equal to TYPE2 for members with no distributed transverse loading. Then =max, where is the ratio of smaller to larger moments about the second cross-section axis at the element ends.
Set this parameter equal to TYPE3 for members with distributed transverse loading. Then =min
, where is the compressive axial stress and 
is the Euler buckling stress corresponding to the second cross-section direction.
First (and only) data line:
, buckling reduction factor in the first cross-section direction.
, buckling reduction factor in the second cross-section direction.
If a blank is given on the data line, it is interpreted as zero. If a blank or zero value is given on the data line and either the AXIS1 or AXIS2 parameter is included for this reduction factor, the parameter value will override the zero value given on the data line. If a nonzero value is given on the data line and the AXIS1 or AXIS2 parameter is specified for the same reduction coefficient, an error is issued.