*BUCKLING REDUCTION FACTORS

Define buckling reduction factors for buckling strut response of frame elements with PIPE sections.

This option is used to define two coefficients used in the ISO equation, which predicts Pc⁢r, 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=σ0 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=σ0 option.

Related Topics
In Other Guides
Frame elements
Frame section behavior
Buckling strut response for frame elements

ProductsAbaqus/Standard

TypeModel data

LevelPartPart instanceModel

Optional parameters

AXIS1

Include this parameter to define the method for calculating the buckling reduction factor cm⁢1 for bending about the first cross-section direction.

Set AXIS1=TYPE1 (default) to set cm⁢1 to the constant value of 0.85.

Set AXIS1=TYPE2 for members with no distributed transverse loading. Then cm⁢1=max(0.6-0.4⁢M1/M2, 0.4), where M1/M2 is the ratio of smaller to larger moments about the first cross-section axis at the element ends.

Set AXIS1=TYPE3 for members with distributed transverse loading. Then cm⁢1=min(1.0-0.4⁢fc/Fe⁢1, 0.85), where fc is the compressive axial stress and Fe⁢1 is the Euler buckling stress corresponding to the first cross-section direction.

AXIS2

Include this parameter to define the method for calculating the buckling reduction factor cm⁢2 for bending about the second cross-section direction.

Set AXIS2=TYPE1 (default) to set cm⁢2 to the constant value of 0.85.

Set AXIS2=TYPE2 for members with no distributed transverse loading. Then cm⁢2=max(0.6-0.4⁢M1/M2, 0.4), where M1/M2 is the ratio of smaller to larger moments about the second cross-section axis at the element ends.

Set AXIS2=TYPE3 for members with distributed transverse loading. Then cm⁢2=min(1.0-0.4⁢fc/Fe⁢2, 0.85), where fc is the compressive axial stress and Fe⁢2 is the Euler buckling stress corresponding to the second cross-section direction.

Data line to define the buckling reduction coefficients

First (and only) data line

  1. cm⁢1, buckling reduction factor in the first cross-section direction.

  2. cm⁢2, 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.