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. The term column applies especially to a large round support (the shaft of the column) with a capital and a base or pedestal[1] which is made of stone, or appearing to be so. A small wooden or metal support is typically called a post, and supports with a rectangular or other non-round section are usually called piers. For the purpose of wind or earthquake engineering, columns may be designed to resist lateral forces. Other compression members are often termed "columns" because of the similar stress conditions. Columns are frequently used to support beams or arches on which the upper parts of walls or ceilings rest. In architecture, "column" refers to such a structural element that also has certain proportional and decorative features. A column might also be a decorative element not needed for structural purposes; many columns are "engaged", that is to say form part of a wall. Contents 1 History 2 Structure 2.1 Nomenclature 2.2 Equilibrium, instability, and loads 2.3 Extensions 2.4 Foundations 3 Classical orders 3.1 Doric order 3.2 Tuscan order 3.3 Ionic order 3.4 Corinthian order 3.5 Composite order 3.6 Solomonic 4 Pillar tombs 5 Gallery 6 See also 7 References History[edit] Illustration of Doric (left three), Ionic (middle three) and Corinthian (right two) columns. All significant
Plan, front view and side view of a typical
Some of the most elaborate columns in the ancient world were those of
the Persians, especially the massive stone columns erected in
Persepolis. They included double-bull structures in their capitals.
The
v t e Mechanical failure modes Buckling
Corrosion
Table showing values of K for structural columns of various end conditions (adapted from Manual of Steel Construction, 8th edition, American Institute of Steel Construction, Table C1.8.1) As the axial load on a perfectly straight slender column with elastic material properties is increased in magnitude, this ideal column passes through three states: stable equilibrium, neutral equilibrium, and instability. The straight column under load is in stable equilibrium if a lateral force, applied between the two ends of the column, produces a small lateral deflection which disappears and the column returns to its straight form when the lateral force is removed. If the column load is gradually increased, a condition is reached in which the straight form of equilibrium becomes so-called neutral equilibrium, and a small lateral force will produce a deflection that does not disappear and the column remains in this slightly bent form when the lateral force is removed. The load at which neutral equilibrium of a column is reached is called the critical or buckling load. The state of instability is reached when a slight increase of the column load causes uncontrollably growing lateral deflections leading to complete collapse. For an axially loaded straight column with any end support conditions, the equation of static equilibrium, in the form of a differential equation, can be solved for the deflected shape and critical load of the column. With hinged, fixed or free end support conditions the deflected shape in neutral equilibrium of an initially straight column with uniform cross section throughout its length always follows a partial or composite sinusoidal curve shape, and the critical load is given by f c r ≡ π 2 E I m i n L 2 ( 1 ) displaystyle f_ cr equiv frac pi ^ 2 textit E I_ min L ^ 2 qquad (1) where E = elastic modulus of the material, Imin = the minimal moment of inertia of the cross section, and L = actual length of the column between its two end supports. A variant of (1) is given by f c r ≡ π 2 E T ( K L r ) 2 ( 2 ) displaystyle f_ cr equiv frac pi ^ 2 E_ T ( frac KL r )^ 2 qquad (2) where r = radius of gyration of [column]cross-section which is equal to the square root of (I/A), K = ratio of the longest half sine wave to the actual column length, and KL = effective length (length of an equivalent hinged-hinged column). From Equation (2) it can be noted that the buckling strength of a column is inversely proportional to the square of its length. When the critical stress, Fcr (Fcr =Pcr/A, where A = cross-sectional area of the column), is greater than the proportional limit of the material, the column is experiencing inelastic buckling. Since at this stress the slope of the material's stress-strain curve, Et (called the tangent modulus), is smaller than that below the proportional limit, the critical load at inelastic buckling is reduced. More complex formulas and procedures apply for such cases, but in its simplest form the critical buckling load formula is given as Equation (3), f c r ≡ F y − F y 2 4 π 2 E ( K L r 2 ) ( 3 ) displaystyle f_ cr equiv F_ y - frac F_ y ^ 2 4pi ^ 2 E left( frac KL r^ 2 right)qquad (3) where Et = tangent modulus at the stress Fcr
A column with a cross section that lacks symmetry may suffer torsional
buckling (sudden twisting) before, or in combination with, lateral
buckling. The presence of the twisting deformations renders both
theoretical analyses and practical designs rather complex.
Eccentricity of the load, or imperfections such as initial
crookedness, decreases column strength. If the axial load on the
column is not concentric, that is, its line of action is not precisely
coincident with the centroidal axis of the column, the column is
characterized as eccentrically loaded. The eccentricity of the load,
or an initial curvature, subjects the column to immediate bending. The
increased stresses due to the combined axial-plus-flexural stresses
result in a reduced load-carrying ability.
Great Hypostyle Hall, Karnak, Egypt' Columns found at the Temple of Apollo in Delphi Modern column grid in a car park or parking garage At right, two of the Solomonic columns brought to Rome by Constantine, in their present-day location on a pier in St. Peter's Basilica, Rome. In the foreground at left is part of Bernini's Baldachin, inspired by the original columns. Ionic capital Tuscan columns can be seen at the University of Virginia. Church of San Prospero, Reggio Emilia, Italy Construction of
These are composed of stacked segments and finished in the Corinthian style (Temple of Bel, Syria) The pillars of Bankstown Reservoir, Sydney Reused Roman columns and capitals in the Great Mosque of Kairouan See also[edit] Wikimedia Commons has media related to Columns. Capital Entasis Huabiao Marian and Holy Trinity columns Pilaster Pole (other) Spur (architecture) Stanchion References[edit] ^ "
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