What is Effective Length of Column?
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There are different types of structural systems in use of which framed structural system is mostly used nowadays. This frame system have different members i.e. foundation, column, beam slab etc. Structural columns are the members which are spanned across the full height of the structure and as well as below the ground. Column has a crucial part in load transfer mechanism as all load form top floor of structure is transferred to bottom most footing by column. So, structural column is one of the members in a structural system which is present in substructure as well as superstructure.
Basically length of column can be said as vertical distance between two floors or between two tie levels. According to structural point of view length of column is the distance between two points where a column gets its fixidty of support so its movement is restrained in all directions.
Structurally effective length of column is defined as height between the points of contraflexure of the buckled column i.e. between two floors basically.
The effective length of column depends on whether the frame is sway or no-sway and on the bending stiffnesses of the beam meeting at the column. If the beam is very stiff, it will not bend significantly under the action of loads, and will provide fixity to the column and if the beam is flexible it will bend easily and will not provide lateral restraints. Depending on above situations the effective length of column for different situations are as follows:
EFFECTIVE LENGTH OF COLUMN
End-restrained of Column
|01.||Effectively held in position and restrained against rotation at both ends||0.5 L|
|02.||Effectively held in position at both ends and restrained against rotation at one end||0.7 L|
|03.||Effectively held in position at both ends but not restrained against rotation||1.0 L|
|04.||Effectively held in position and restrained against rotation at one end, and at other end restrained against rotation but not held in position||2.0 L|