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Total Loss of Prestress

1. Creep is the time dependent deformation of concrete due to permanent prestress forces, causing compressive stress at the level of steel and resulting in creep strain. 2. Total loss of prestress is caused by elastic shortening, shrinkage of concrete, creep of concrete, and relaxation of steel. 3. Prestress loss is calculated by deducting initial prestress obtained after anchorage from the jacking stress used to pull the wire, accounting for losses from elastic strain, creep strain, shrinkage, and steel relaxation.

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53 views2 pages

Total Loss of Prestress

1. Creep is the time dependent deformation of concrete due to permanent prestress forces, causing compressive stress at the level of steel and resulting in creep strain. 2. Total loss of prestress is caused by elastic shortening, shrinkage of concrete, creep of concrete, and relaxation of steel. 3. Prestress loss is calculated by deducting initial prestress obtained after anchorage from the jacking stress used to pull the wire, accounting for losses from elastic strain, creep strain, shrinkage, and steel relaxation.

Uploaded by

shaikh a n
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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1.

Creep strain = x Elastic strain


2. vc) Creep of Concrete:
3. 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.

4. relaxation of steel

TOTAL LOSS OF PRESTRESS:


5. elastic shortening

6. shrinkage of concrete

7. creep of concrete

8. 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

Elastic strain =

is the stress in concrete at the level of steel.

Loss in prestress = creep strain x


x

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