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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

Prestressing force and Ecentricity


Prestressing Force & Eccentricity

Once the actual Zt and Zb have been determined, the next step is to determine what combination of prestress force, P and eccentricity, e, to use at that section. Taking each stress limit in turn:

 

Tensile Stress at Transfer

This is a linear equation in P1 and e. Therefore a plot of these two quantities will give a region that is acceptable and a region that is not acceptable, according to the inequality.

 

Compressive Stress at Transfer

Another linear equation which gives the feasible region

 

Compressive Stress in Service

This equation can again be graphed to show the feasible region. However, this line can have a positive or negative slope. When the slope is negative, P1 must be under the line; when the slope is positive, P1 must be over the line. A simple way to remember this is that the origin is always not feasible.

 

Tensile Stress in Service

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