Prestressed Concrete: Post-tensioning

Introduction

This article provides a primer for concept and detail design for post-tension member design.

Post-tensioning Systems

Components and Material for Post-tensioning

Prestressing strand

Effective Prestress

Force in prestressing steel, after all, prestress losses is called effective prestress

Load-Balance Method

The serviceability check ( maximum compression stress, maximum tensile stress) is performed for the transfer and service condition ( sustained load and total load) and construction stage.

to explain the procedure of the load-balancing method three simply supported beams with tendon layout

1. Parabolic ( for Uniformly distributed live load)
2. Single point depressed ( for single concentrated live load)
3. Two-point depressed ( for two concentrated live loads)

Parabolic Layout

Single-point depressed

Two-points depressed

Code Checks

Serviceability Check at the transfer

At prestress force transfer (age i Days), concrete cylindrical strength fci'

Serviceability Check at Service

Calculation of Section

References

• Design of Prestressed Concrete Structures, TY Lin
• Prof. Mohan Kalani, Prestressed Concrete Design, IIT Bombay
• VSL
• Freyssinet
• BBR
• CCL