JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD

Pre-Requisites

Reinforced Concrete Design

Course Objectives

Prestressing is the techniques often used in bridges and other structural

elements for longer span and hearer loads. This subject covers various aspects of prestressing and design techniques to give the student an overall exposure in the analysis and design of Prestressed concrete structures.

Course Outcomes

At the end of the course, the student will be able to:

• Able to design prestressed concrete structures
• Understand the concepts of pre-stressing in concrete structures and identify the Materials for pre-stressing
• Analysis of sections for flexure and shear
• Understand the concepts of transfer of prestress in pretensioned members
• Analysis of composite beams and importance of deflections

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 Post tensioning 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 pre- tensioned and post-tesnioned 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 IS 1343-2012 code provisions

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

R16 B.TECH CIVIL ENGG.

Guyon, Magnel, Zienlinski and Rowe’s methods – Anchorage zone reinforcement- IS 1343- 2012 code 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.

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 R16 B.TECH CIVIL ENGG.