JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD

Pre-Requisites

Reinforced Concrete Design

Course Objectives

The objectives of the course are to

• Understand the principles & necessity of prestressed concrete structures.
• Know different techniques of prestressing.
• Get the knowledge on various losses of prestress.
• Understand Analysis and design of prestressed concrete members.

Course Outcomes

After the completion of the course student should be able to

• Acquire the knowledge of evolution of process of prestressing.
• Acquire the knowledge of various prestressing techniques.
• Develop skills in analysis design of prestressed structural elements as per the IS codal provisions

UNIT - I

Introduction: Historic development- General principles of prestressing pretensioning and post tensioning- Advantages and limitations of Prestressed concrete- General principles of PSC- Classification and types of prestressing- Materials- high strength concrete and high tensile steel their characteristics.

UNIT - II

Methods and Systems of prestressing: Pretensioning and Posttensioning methods and systems of prestressing like Hoyer system, Magnel Blaton system, Freyssinet system and Gifford- Udall System- Lee McCall system.Losses of Prestress: Loss of prestress in pretensioned and posttesnioned members due to various causes like elastic shortage of concrete, shrinkage of concrete, creep of concrete, relaxation of stress in steel, slip in anchorage, frictional losses.

UNIT - III

Flexure: Analysis of sections for flexure- beams prestressed with straight, concentric, eccentric, bent and parabolic tendons- stress diagrams- Elastic design of PSC slabs and beams of rectangular and I sections- Kern line – Cable profile and cable layout. Shear: General Considerations- Principal tension and compression- Improving shear resistance of concrete by horizontal and vertical prestressing and by using inclined or parabolic cables- Analysis of rectangular and I beams for shear – Design of shear reinforcements- IS Code provisions.

UNIT - IV

Transfer of Prestress in Pretensioned Members: Transmission of prestressing force by bond – Transmission length – Flexural bond stresses – IS code provisions – Anchorage zone stresses in post tensioned members – stress distribution in End block – Analysis by Guyon, Magnel, Zienlinski and Rowe’s methods – Anchorage zone reinforcement- IS Provisions

UNIT - V

Composite Beams: Different Types- Propped and Unpropped- stress distribution- Differential shrinkage- Analysis of composite beams- General design considerations. Deflections: Importance of control of deflections- Factors influencing deflections – Short term deflections of uncracked beams- prediction of long time deflections- IS code requirements.

R18 B.TECH CIVIL ENGG. III YEAR

REFERENCES:

• 1. Prestressed concrete by Krishna Raju, Tata Mc Graw Hill Book – Co. New Delhi.
• 2. Design of prestress concrete structures by T.Y. Lin and Burn, John Wiley, New York.
• 3. Prestressed concrete by S. Ramamrutham Dhanpat Rai & Sons, Delhi.
• 4. Prestressed Concrete by N. Rajagopalan Narosa Publishing House R18 B.TECH CIVIL ENGG. III YEAR