Columns are classified as short or long depending on their slenderness ratios. Short columns
usually, fail when their materials are overstressed and long columns usually fail due to buckling
which produces secondary moments resulting from the P – D effect.
Columns are classified according to the way they are reinforced into tied and spirally reinforced
columns. Columns are usually reinforced with longitudinal and transverse reinforcement. When
this transverse reinforcement is in the form of ties, the column is called “tied”. If the transverse
reinforcement is in the form of helical hoops, the column is called “spirally reinforced”.
Since the failure of columns often cause extensive damage, they are designed with a higher factor of
safety than beams.
Columns are divided into three types according to the way they are reinforced:
A tied column is a column in which the longitudinal reinforcement bars are
tied together with separate smaller diameter transverse bars (ties) spaced at some interval along
the column height. These ties help to hold the longitudinal reinforcement bars in place during
construction and ensure the stability of these bars against local buckling. The cross sections of such
columns are usually square, rectangular, or circular in shape. A minimum of four bars is used in
rectangular and circular cross-sections.
They are columns in which the longitudinal bars are arranged in a circle surrounded by a closely
spaced continuous spiral. These columns are usually circular or square in
shape. A minimum of six bars is used for longitudinal reinforcement.
A composite column is a column made of structural steel shapes or pipes surrounded by or filled
by concrete with or without longitudinal reinforcement.
|Name||Design of Columns Spreadsheet|
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