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Total Loss of Prestress

Creep is the time-dependent deformation of concrete due to permanent prestressing forces. When concrete is prestressed, the prestressing steel applies a compressive stress on the concrete. Over time, the concrete will deform and strain as a result of this constant compressive stress through a process called creep. The amount of loss of prestress due to creep is calculated based on the creep strain of the concrete, which is determined by multiplying the elastic strain by a creep coefficient.

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21 views2 pages

Total Loss of Prestress

Creep is the time-dependent deformation of concrete due to permanent prestressing forces. When concrete is prestressed, the prestressing steel applies a compressive stress on the concrete. Over time, the concrete will deform and strain as a result of this constant compressive stress through a process called creep. The amount of loss of prestress due to creep is calculated based on the creep strain of the concrete, which is determined by multiplying the elastic strain by a creep coefficient.

Uploaded by

shaikh a n
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as DOCX, PDF, TXT or read online on Scribd
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1.

vc) Creep of Concrete:


2. Creep is the time dependent deformation due to permanent force. In
prestressed concrete, prestress is the permanent force in the member,
causing compressive stress at the level of steel. Hence there is creep
strain in the member.

3. relaxation of steel

TOTAL LOSS OF PRESTRESS:


4. elastic shortening

5. shrinkage of concrete

6. creep of concrete

7. relaxation of steel

and Specifications Clear Span 48 ft Clear width 29 ft Live Loading HS20 Concrete strength fc ’ 3000 psi
Future protective cover 15 pf Grade 40 reinforcement The bridge will consist of six girders By AASHTO
specifications, an allowable concrete stress of fc = 0.40 fc ’ = 1200 psi And an allowable steel stress of fs
= 0.5 fy = 20,If prestress is measured at the time of pulling the wire, the stress
is termed as the jacking stress. Deducting the loss due to anchorage take-up
and friction, initial prestress is obtained. Effective stress is usually the initial
stress minus other four losses namely:

Loss due to

Creep strain = x Elastic strain

Elastic strain =

is the stress in concrete at the level of steel.

Loss in prestress = creep strain x


x

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