Understanding Beams: Behavior, Failure Modes, Stresses, and Types Used in Construction

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Introduction
A beam is a bar, processing length significantly greater than the depth and width. The
classification of the beam is done as moderate deep beams, shallow beams, and deep beams.
Beams are usually loaded in a normal direction to the longitudinal axis, while bars axially loaded
or twisted. The load-supporting action of plates resembles and to a certain extent that of the
beam. Deep beams are those type of beams whose depth are comparable to their spans and
sometimes a beam can also mean some structural elements that resist loads applied laterally to
their axis. There is a different variation that is shown by the behavior of deep beam as a result
of the existence of normal forces due to usual bending moments and shear forces. In
construction, the application of deep beams takes place in water tanks, nuclear reactors and
also underground bunkers. They normally transmit loads executed alongside their dimension to
their endpoints where the loads are transferred to walls, foundations, and columns. Beam
maybe;
 Both ends are supported to evade spin.
 Extending more than two supports.
 Supported at both ends to allow free rotation to take place.
In most cases in floor framing, beam is braced literally either by other beams framed into it or
by floor construction itself. A random cross section in a beam when exposed to a transverse
load will cause bending of the beam and there are certain effects arising as a result of bending
and these are buckling as well as twisting.

Conditions of equilibrium
The classification of external forces acting on a member can be done as body forces and surface
forces and the concentration of the surface force takes place when it is acting as a point and it
may be distributed uniformly or non-uniformly over a finite area. All forces acting on a member
are considered external forces but in the case of body forces, it acts slowly and steadily in static
loading.
The behavior of deep beams
When an effective ratio plan (L) to total depth (D) is below 2.0 and that of the continuous beam
is below than 2.5 is when a beam can be considered as a deep beam. An appropriate span is
simply the distance between the middle and the supports or 1.15 times the clear span
whichever is less (Nielsen, 2010, p. 275). The classification of beams can be done based on
Deep beam with or without openings, Continuous Deep Beam and Simply supported Deep
Beam (Hyun-Moo, 2008, p. 216).
The behavior of deep beam differs from the beams with normal sizes, needing special
considerations, designing as well as detailing of reinforcement. Their strength is controlled by
shear because of their proportion. The deep beam shear strength can be two to three times
superior to that predicted using equations. The transfer of load in the deep beam is done
directly from the application are to be supported by diagonal compression strut. The formation
of diagonal strut takes place in a direction parallel to a line from the load to support isolated

compression strut, which seems to be horizontal compression in the concrete and the tension
in the main reinforcement for load equilibration.
The designing and casting of beam take place for two points loading and two shear spans
200mm and 250mm. For design purpose, application of 50kN point load is applied on deep
beams. Shear rather than flexure assist in controlling the strength of deep beams so long as the
normal quantity of longitudinal reinforcement is used (Ng, 2015, p. 412). The compression in
diagonal direction and tension in a perpendicular direction is caused by the action of shear in
the beam web.
Failure Modes
The failure modes of the deep beam can be divided into two major categories;
Mode 1- Flexural failure mode
Mode 2-Shear failure modes
The shear failure mode can also be divided into various sub-divisions which include;
 Shear compression stress where the development of diagonal crack into the
compressive zone causes the RC beam to fail.
 Compressive failure or shear proper of struts which are realized in beams having small
shear span to depth ratio and this will also make the steeping line to be deep.
 Diagonal tension failure which entails the thrust line becoming very eccentric giving rise
to flexural failure in the compressive zone. This kind of failure arises from extension
tensile crack in the compressive region to flexural load (Nielsen, 2010, p. 74).