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Beams are linear structural members, which resists the imposed
loading primarily by developing bending and shear stress in
it. They are usually provided at floor level to support the
load of floor decking. They are designed for bending, shear,
deflection and bearing.
Based on the support system provided structural beams can
be classified into following types:
i) Simply Supported beams: Beams having only two supports,
one at each end.
ii) Continuous Beam: Beam supported on more than two supports
iii) Cantilever Beam: Beam whose one end is resting on the
support and other end is free.
Based on the material used beams can be classified into
following types:
i) Lumber Beams: These beams include lumber beam, Glulam
beams, LVL beams and ceiling beams.
ii) Concrete Beams: These beams include rectangular beams,
T- shapes beams, L- Shape beams and turndown beams.
iii) Steel Beams: These beams include I beams and angle beams.
iv) Flitched beams: These beams consist of steel plates flitched
between lumber beams. This increases the moment of inertia
of the beam.
Beams can be designed by following methods:
i) Allowable Stress Design Method: This method is based on
the principle that actual stress in the material should not
exceed the permissible stress permitted in the material. The
member is designed for working load condition. Lumber beams,
steel beams and flitched beams are designed by this method.
Permissible beam deflections are governed by beam span.
ii) Ultimate Strength Design Method: This method is based
on the ultimate load theory. In this method factored load
is used to design the member for strength, and working load
is used to check for serviceability condition. Concrete beams
are designed by this method.
Wood beams for different combinations of loads and different
material types can be designed using following beam design
modules:
Special attention is given to the following factors while
designing beams:
i) Bending (including lateral stability)
ii) Shear
iii) Deflection
iv) Bearing
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