Beams and Columns

Beams

Beams are defined as horizontal load carrying member in a structure. Reinforced cement concrete, concrete, prestressed concrete and steel I sections are used as beams to support the slabs.

Classified:

ü Simply supported beam

ü Rigidly fixed beam

ü Cantilever beam

ü Over hanging beam

ü Continuous beam

Simply supported beam:

If the ends of a beam are supported freely by columns it is called simply supported beam

Rigidly fixed beam:

It the two ends of a beam is rigidly fixed in walls then it is called fixed beams. In such cases, the moment is induced at supports because it will not allow rotation.

Cantilever beam:

If a beam is fixed in one end and the other end is free then it is called cantilever beam.

Overhanging beam:

If a beam having its end portion extended beyond the support, it is called overhanging beam.

Continuous beam:

If a beam is supported on more than two supports, then it is known as continuous beam.

Columns

The vertical load carrying member of a structure is called column. They are constructed of timber, stone, reinforced cement concrete of steel section.

Classified:

ü Long column

ü Short column

Long column

The ratio of effective length to least later dimension is less than 12 called as long column

Short column

The ratio of effective length to least later dimension is more than 12 called as long column

Reinforced cement concrete column

Usually the reinforced cement concrete column are cast in-situ type. They may be constructed in square, rectangular, circular shapes. Vertical reinforcements or main reinforcements are provided to take up major load coming over the column. Generally the diameter of vertical reinforcement may vary from 10mm to 40mm.Longitudinal reinforcement bars should not be less than 0.8% and not more than 6% of the cross sectional area of the column. The diameter of lateral reinforcement may vary from 6mm to 10mm.

In the multi storyed buildings, the section of the column in upper stories may be reduced as they have to carry lesser loads. But the centre lines of various columns of different stories must coincide in a same vertical line.

Steel columns

The various cross sections of steel columns are shown in fig. Struts of one or two angles are used as compression member in roof trusses. Latticed columns made up of channels or angles connected by lattice bars are often used where light loads are to be supported on long columns. battened columns made up of channels or angles connected only batten plate are also used as column. Rolled H-columns which are available in depths ranging from 150 mm to 500 mm and are now commonly used in steel Skelton construction.