Reinforced concrete is produced when steel reinforcement bars ("rebars"),
plates or fibers are incorporated into concrete. Plain
Concrete itself is very weak in tension. Reinforcement gives extra
tensile strength to concrete. The advent of reinforced concrete
brought into existence a lot of high rise and cost-effective buildings
with reduced construction duration. Reinforced concrete can be classified as
(i) precast concrete and (ii) cast in-situ concrete.
Reinforced concrete can
be used for many types of structures and
components, including beams, slabs, walls,
columns, foundations and more.
Principles of Reinforced concrete
The principles and methods for reinforced concrete are being
constantly revised as a result of theoretical and experimental
Two philosophies of design have been established;
1. Working Stress Method with a focus on conditions of service load.
(It has become obsolete now).
2. Strength Design Method with a focus on conditions at loads
greater than service loads when failure may happen.
Strength Design Method has adopted two load factors; U (overload
factor) and φ
(strength reduction factor) for safety
Strength design method requires that Design Strength
(axial force, shear force,bending moment) should be greater than
or equal to Factored Load (required strength).
Design Strength is obtained by multiplying the nominal strength
by strength reduction factor ( φ).Nominal strength of an element
is calculated by static equilibrium and compatibility of stress
Factored loads are obtained by multiplying the service load by
overload factor U.
Moment of Inertia
For different sections including I-section and
Easy to use calculator for different loads on beams
A collection of illustrated solved examples for civil
Calculate the strength of reinforced concrete beams
A collection of quiz in different areas of civil
Calculate Bending moments for simply supported beams
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Analysis of Reinforced Concrete Beams
The nominal strength of a reinforced concrete
beam is expected to be achieved when the strain in the extreme
compression fiber is equal to the crushing strain of concrete (0.003).
There are two basic modes of failure of flexural reinforced
(i) Concrete controlled (brittle mode) also known as
over-reinforced: The stress in steel is less than the yield stress. In
this mode of failure a sudden collapse occurs. It is not desirable.
(ii) Steel controlled (ductile mode) also known as under
reinforced: yielding takes place in steel i.e., The stress in steel
reaches the yield stress and the strain in steel is
≥ yield strain. The maximum compressive
strain in concrete is less than the failure strain.
Balanced condition is an
intermediate point between brittle and ductile failure modes. The
amount of reinforcement required for a balanced section is known as a
balanced reinforcement. The designer must select the amount of
reinforcement less than the balanced reinforcement in order to ensure
that brittle failure does not take place.
beam can be
singly reinforced (rebar only in tension zone of the section) or
doubly reinforced (rebar in tension and compression zones of the section).
To learn more about strength of reinforced concrete beam please
example 9-1 ,
Problem for civil engineers
For strength of RC beam visit
Easy to use calculator for solving Indeterminate beams with
Bending Moment & Shear Force Calculation
for Overhanging beam with different loads
Fixed Beam Calculator
Shear force and bending moment calculations for different loading
cases of Fixed beam