A
rebar
or reinforcing bar refers to a common steel bar, which is commonly
used in reinforced concrete and reinforced masonry structures. Rebar
are generally formed from carbon steel and for better anchoring into the
concrete, these rebar are given ridges. Though concrete is very strong
in compression, it is weak in tension. By casting rebar into the
concrete, this imbalance between compression and tension is nullified.
Masonry structures and the mortar holding them
together have similar properties to concrete and also have a limited
ability to carry tensile loads. Some standard masonry units like blocks
and bricks are made with strategically placed voids to accommodate
rebar, which is then secured in place with grout. This combination is
known as reinforced masonry.
While any material with sufficient tensile strength
could conceivably be used to reinforce concrete, steel and concrete
have similar coefficients of thermal expansion: a concrete structural
member reinforced with steel will experience minimal stress as a result
of differential expansions of the two interconnected materials caused
by temperature changes.
Steel has an expansion co-efficient nearly equal to
that of modern concrete. If this weren't so, it would cause problems
through additional longitudinal and perpendicular stresses at
temperatures different of the temperature of the setting. Although
rebar has ridges that bind it mechanically to the concrete, it can
still be pulled out of the concrete under high stresses, an occurrence
that often precedes a larger-scale collapse of the structure. To
prevent such a failure, rebar is either deeply embedded into adjacent
structural members, or bent and hooked at the ends to lock it around
the concrete and other rebar. This first approach increases the friction
locking the bar into place, while the second makes use of the high
compressive strength of concrete.
U.S. Imperial sizes: Imperial bar designations
represent the bar diameter in fractions of 1⁄8 inch, such that #8 = 8⁄8
inch = 1 inch diameter. Area = (bar size/9)2 such that area of #8 = (8/9)2 = 0.79 in2.
This applies to #8 bars and smaller. Bars higher in number have a
slightly larger diameter than the one computed using the 1⁄8 inch
formula.
Canadian metric sizes: Metric bar designations represent the nominal bar diameter in millimeters, rounded to the nearest 5 mm.
GRADES
Rebar is available in different grades and specifications that
vary in yield strength, ultimate tensile strength, chemical composition,
and percentage of elongation.
The grade designation is equal to the minimum yield strength of
the bar in ksi (1000 psi). For instance grade 60 rebar has a minimum
yield strength of 60 ksi. Rebar is typically manufactured in grades of
40, 60, and 75.
Common specifications are:
:: ASTM A 615 Deformed and plain carbon-steel bars for concrete reinforcement.
:: ASTM A 706 Low-alloy steel deformed and plain bars for concrete reinforcement.
:: ASTM A 955 Deformed and plain stainless-steel bars for concrete reinforcement.
:: ASTM A 996 Rail-steel and axle-steel deformed bars for concrete reinforcement.
Historically in Europe, rebar comprised mild steel material with a
yield strength of approximately 250 N/mm². Modern rebar comprises
high-yield steel, with a yield strength more typically 500 N/mm². Rebar
can be supplied with various grades of ductility, with the more
ductile steel capable of absorbing considerably greater energy when
deformed - this can be of use in design to resist the forces from
earthquakes for example.
Expertise in CAD or expertise in structural engineering is not
enough for
rebar detailing. It’s a perfect combination of the two with
thorough knowledge in preparing detailed drawings as per global
standards. Rebar detailers of
Rebar Detailing India are a perfect combination, who
can offer you rebar detailing as per global standards.
