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Introduction to Prestressed Concrete
Prestressed concrete is a form of concrete used in construction to provide sufficient
precompression in the concrete beam by tensioned steel wires, cables, rods etc
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In prestressing, an initial load on the structure prior to its use
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Prestressed concrete formation is composed of concrete as a structural element and steel
as a prestressing component
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Prestressed concrete defined as:
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A concrete structure where external compressive forces are intentionally used to
overcome tensile stresses caused by unavoidable loads due to gravity, permanent
and variable loads

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Concrete in which there have been introduced internal stresses of such magnitude
and distribution that stresses resulting from given external loadings are encountered
to the desired degree
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k
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Tendons) is a stretched steel element used in concrete
member to impart prestress to the concrete
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Such as Mcallory bars and
Dywidag bar

Macalloy Bars

Dywidbag Bar

Examples of Prestressed Concrete

RC and Prestressed Concrete
Concrete is very strong in compression but weak in tension (its tensile strength varies
from 8% to 14% of compressive strength)
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This causes
serviceability issues and eventually these cracks may cause larger fractures and
collapse of structures
To reduce or to prevent such cracks from developing, a concentric or eccentric force is
imposed in longitudinal direction of the structural elements, by means of steel tendons
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This imposed forced is called prestressing force –a compressive force that prestresses
the section along the span of structural element prior to the application of gravity
(permanent) and variable loads
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Post-tensioning: it is a method used for reinforcing concrete or other materials with
high strength steel stands or bars such as tendons that are stretched out once the
concrete is settled and hardened
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During the transfer of prestress, the member undergoes elastic shortening
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Post Tensioning System
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The ducts for the tendons (or strands) are placed along with the reinforcement before
the casting of concrete
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The duct prevents
contact between concrete and the tendons durin

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