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  • Prestresed Concrete
    • Introduction to prestressed concrete
    • Methods of prestressing
    • Design of PSC members
    • Prestressing force and Ecentricity
    • Ecentricity limits and tendon profile
    • Losses in prestressed concrete structures

  • tanks
    • Introduction to water tanks
    • Load conditions and flexure details for water tanks
    • Minimum and Maximum reinforcement for tanks
    • Slab design for Tanks
    • Design Requirement of Concrete in tanks
    • General design requirements for members of a tank
    • Circular tank Analysis
    • Numerical on the analysis of Circular water tank
    • Design of Rectangular tanks
    • Numerical on Rectangular water tank
    • Underground Tanks
    • Overhead tanks

  • Retaining walls
    • Retaining walls and their types
    • Earth Pressure and Stablity requirements
    • Proportioning and design of cantilever and counterfort walls
    • Numerical on design of a Retaining wall

  • footings
    • Introduction to footings
    • Soil Pressure under Isolated footings
    • General Design Considerations for Footings
    • Special case of Footing
    • Numerical on footings
    • Design of Combined Footing

  • Flat slabs
    • Introduction to flat slabs
    • Proportioning of flat slabs
    • Determination of bending moment and shear force
    • Slab reinforcement
    • Numericals of flat slab

Branch : Civil Engineering
Subject : Design of Concrete Structures-II
Unit : Prestresed Concrete

Ecentricity limits and tendon profile


Eccentricity Limits and Tendon Profile

Since the moments change along the length of a beam, we must change some aspect of the prestress also. The only remaining variable is the eccentricity.

Tension on Top at Transfer

We determine an expression for the eccentricity in terms of the other knowns:

Hence we have a lower limit for the eccentricity as:

Tension on the Bottom in Service

Using

Hence we have an upper limit for the eccentricity as:

Since the upper and lower kerns (the Zt/A and Zb/A quantities) are constant for constant geometry, and since P is also constant, it can be seen that the cable limits follow the same profile as the bending moment diagrams at transfer and in service.

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