Buckling Coefficient

on . Posted in Dimensionless Numbers

Buckling coefficient, abbreviated as K, also called slenderness ratio, a dimensionless number, is used in structural engineering to assess the stability of a slender structural element under axial compression that can lead to failure.  When a structure is subjected to compressive stress, buckling may occure.  Buckling is characterized by a sudden sideways deflection of a structural member.  The formula for the buckling coefficient depends on the type of end support conditions and the geometry of the column.

When a slender structural member is subjected to compressive forces, it may buckle, which refers to a sudden, uncontrollable lateral deflection or deformation.  Buckling can lead to structural failure if not properly addressed in the design.

 

Buckling coefficient formula

Fixed-Fixed (both ends are fixed)

Pinned-Pinned (both ends are hinged or pinned)

\( K \;=\;  \sqrt{ \lambda \; I \;/\; k \; A_c \; l^2 }  \)     (Buckling Coefficient)

\( \lambda \;=\; K^2 \; k \; A_c \; l^2 \;/\; I  \)

\( I \;=\; K^2 \; k \; A_c \; l^2 \;/\; \lambda \)

\( k \;=\; \lambda \; I \;/\; K^2 \; A_c \; l^2 \)

\( A_c \;=\; \lambda \; I \; k \;/\; K^2 \; l^2 \)

\( l \;=\; \sqrt{ \lambda \; I  \;/\;  k \; A_c \; K^2 }  \)

Symbol English Metric
\( K \) = Buckling Coefficient (Fixed-fixed and Pinned-pinned) \(dimensionless\) \(dimensionless\)
\( \lambda \)  (Greek symbol lambda) = Material Elastic Modulus \(lbf \;/\; in^2\) \(Pa\)
\( I \) = Second Moment of Inertia \(in^4\) \(mm^4\)
\( k \) = Effective Length Factor (which Depends on the End Conditions) \(in\) \(mm\)
\( A_c \) = Material Area Cross-section \(in^2\) \(mm^2\)
\( l \) = Length of the Member \(in\) \(mm\)

 

Buckling coefficient formula

Fixed-Free (one end is fixed, and the other end is free)

Pinned-Free (one end is pinned, and the other end is free)

\( K \;=\; \sqrt{ 2 \; \lambda \; I \;/\; k \; A_c \; l^2 }  \)     (Buckling Coefficient)

\( \lambda \;=\; K^2 \; k \; A_c \; l^2 \;/\; 2 \; I \)

\( I \;=\; K^2 \; k \; A_c \; l^2 \;/\; 2 \; \lambda \)

\( k \;=\; K^2 \;/\; 2 \; \lambda \; A_c \; l^2 \)

\( A_c \;=\; K^2 \; k \; l^2 \;/\; 2 \; \lambda \; I \)

\( l \;=\; \sqrt { k \; A_c \;/\; 2 \; \lambda \; I \; K^2 }  \)

Symbol English Metric
\( K \) = Buckling Coefficient (Fixed-free and Pinned-free) \(dimensionless\) \(dimensionless\)
\( \lambda \)  (Greek symbol lambda) = Material Elastic Modulus \(lbf \;/\; in^2\) \(Pa\)
\( I \) = Second Moment of Inertia \(in^4\) \(mm^4\)
\( k \) = Effective Length Factor (which Depends on the End Conditions) \(in\) \(mm\)
\( A_c \) = Area Cross-section of Material \(in^2\) \(mm^2\)
\( l \) = Length of the Member \(in\) \(mm\)

 

P D Logo 1 

Tags: Coefficient Strain and Stress Structural Steel Structural