A compression member is a structural element that primarily resists forces, which act to shorten or compress the member along its length. Commonly found in engineering and architectural structures, such as
columns
A column or pillar in architecture and structural engineering is a structural element that transmits, through compression, the weight of the structure above to other structural elements below. In other words, a column is a compression member ...
,
struts, and braces, compression members are designed to withstand loads that push or press on them without buckling or failing. The behavior and strength of a compression member depends on factors like material properties, cross-sectional shape, length, and the type of loading applied. These components are critical in frameworks like
bridges
A bridge is a structure built to span a physical obstacle (such as a body of water, valley, road, or railway) without blocking the path underneath. It is constructed for the purpose of providing passage over the obstacle, which is usually somet ...
, buildings, and
towers
A tower is a tall Nonbuilding structure, structure, taller than it is wide, often by a significant factor. Towers are distinguished from guyed mast, masts by their lack of guy-wires and are therefore, along with tall buildings, self-supporting ...
, where they provide stability and support against vertical and lateral forces. In buildings,
posts and
column
A column or pillar in architecture and structural engineering is a structural element that transmits, through compression, the weight of the structure above to other structural elements below. In other words, a column is a compression member ...
s are almost always compression members, as are the ''top chord'' of
truss
A truss is an assembly of ''members'' such as Beam (structure), beams, connected by ''nodes'', that creates a rigid structure.
In engineering, a truss is a structure that "consists of two-force members only, where the members are organized so ...
es in bridges, etc.
Design
For a compression member, such as a column, the principal stress primarily arises from axial forces, which act along a single axis, typically through the
centroid
In mathematics and physics, the centroid, also known as geometric center or center of figure, of a plane figure or solid figure is the arithmetic mean position of all the points in the figure. The same definition extends to any object in n-d ...
of the member cross section.
As detailed in the article on
buckling
In structural engineering, buckling is the sudden change in shape (Deformation (engineering), deformation) of a structural component under Structural load, load, such as the bowing of a column under Compression (physics), compression or the wrin ...
, the slenderness of a compression member, which is defined as the ratio of its effective length to its radius of gyration (
), has a critical role in determining its strength and behavior with axial loading:
* The load capacity of low slenderness (stocky) members is governed by their material
compressive strength
In mechanics, compressive strength (or compression strength) is the capacity of a material or Structural system, structure to withstand Structural load, loads tending to reduce size (Compression (physics), compression). It is opposed to ''tensil ...
;
* Both material strength and buckling influence the load capacity of intermediate members; and
* The strength of slender (long) members is dominated by their buckling load.
Formulas for calculating the
buckling strength of slender members were first developed by
Euler
Leonhard Euler ( ; ; ; 15 April 170718 September 1783) was a Swiss polymath who was active as a mathematician, physicist, astronomer, logician, geographer, and engineer. He founded the studies of graph theory and topology and made influential ...
, while equations like the
Perry-Robertson formula are commonly applied to describe the behavior of intermediate members. The Eurocodes published by the
Comité Européen de Normalisation provide guidance of the calculation of strength for compression members in concrete, masonry, steel and timber.
There are other codes for steel compression members only.
See also
*
Arch
An arch is a curved vertical structure spanning an open space underneath it. Arches may support the load above them, or they may perform a purely decorative role. As a decorative element, the arch dates back to the 4th millennium BC, but stru ...
*
Brown truss
*
List of structural elements
*
Strut
A strut is a structural component commonly found in engineering, aeronautics, architecture and anatomy. Struts generally work by resisting longitudinal compression, but they may also serve in tension.
A stay is sometimes used as a synonym for ...
Notes
External links
Columns and other compression membersNumerical load numbers for reinforced concrete compression members
Columns and entablature
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