Product Overview

DESIGN OF
STRUT SYSTEMS
Beams
Beams are usually defined as horizontal
members which are subjected to vertical
loads such as shelves, platforms or
supports for pipes, conduits or cable
trays.
The following is a brief overview of
common beam configurations:
Simple Beam
An example of a simple beam is a length
of channel placed across two cylinders.
When a load is applied, the channel will
support the load because of its stiffness.
The cylinders serve to support the
channel, but do not interfere with its
natural tendency to flex or bend. Simple
beam analysis is used almost universally
for beam comparisons, even though it is
seldom practical in field installations.
A cable tray or conduit trapeze hanger
closely resembles a simple beam.
Fixed Beam
This type of fixed support restricts the
movement of the ends of the channel
when a load is applied. Because of this,
the stiffness of the channel at the ends
and center is employed to resist the load.
The result is a load capability which is
greater than that of an identical simple
beam.
The fixed beam can be approximated by
bolting or welding a length of channel to
rigid supports.
Cantilever Beam
Cantilever beams are often viewed as
variations of a fixed beam, but they have
special characteristics of their own. One
end of the channel is firmly attached to a
rigid support while the other end remains
completely free.
A
shelf bracket is an example of a
cantilever beam.
Continuous Beam
This beam configuration is commonly
used in lighting installations. The
continuous beam possesses traits of
both the simple and fixed beams. When
equal loads are applied to all spans
simultaneously, the counter-balancing
effect of the loads on both sides of a
support restricts the movement of the
channel at the support, similar to that of
the fixed beam. The end spans behave
substantially like simple beams.
Continuous beam installations can
typically support 20% more load than a
simple beam of the same span with
approximately half the deflection.
Therefore, simple beam data should be
used for a general comparison only. An
example of this configuration is found in a
long run of channel when installed across
several supports to form a number of
spans.
Deflection
Deflection, commonly referred to as “sag”,
is inherent in applying a load to a beam
and cannot be avoided. Any and all
beams will deflect when loaded. The
amount of deflection will vary depending
upon the material and the stiffness or
moment of inertia. The deflection
equations in this section show that
increasing the stif
fness can be increased
by a variety of methods. Increasing the
depth of the channel is the most direct
method.
The material used affects deflection in a
manner which is significantly different
from the way in which it affects load
capacity. The deflection under load is
inversely proportional to a material
property known as the “modulus of
elasticity” designated by “E”.
The modulus of elasticity is dependent
upon the basic composition of the material
and is not necessarily related to the
material’s strength.
Point Load
Point Load
Technical Data
Technical Data
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