Post-Tensioned Concrete Floors Design Handbook – Concrete Society Working Party (KEBT0001)

Post-Tensioned Concrete Floors Design Handbook – Concrete Society Working Party, CONTENTS:

1          INTRODUCTION

1.1       Background

1.2       Advantages of post-tensioned floors

1.3       Structural types considered

1.4       Amount of prestress

1.5       Bonded or unbonded tendon systems

1.5.1    Bonded system

1.5.2    Unbonded system

1.6       Analytical techniques

2          STRUCTURAL BEHAVIOUR

2.1       Effects of prestress

2.2       One-way and two-way spanning floors

2.3       Flexure in one-way spanning floors

2.4       Flexure in flat slabs

2.4.1    Flat slab criteria

2.4.2    Post-tensioned flat slab behaviour

2.5       Shear

3          STRUCTURAL FORM

3.1       Plan layout

3.2       Floor thickness and types

3.3       Effect of restraint to floor shortening

3.4       Durability and fire      resistance

4          MATERIALS

4.1       Concrete

4.2       Tendons

4.2.1    Strand

4.2.2    Tendon protection

4.2.3    Anchorages

4.3       Un-tensioned reinforcement

5          THE DESIGN PROCESS

5.1       Introduction

5.2       Structural layout

5.3       Loading

5.4       Tendon profile and equivalent load

5.5       Prestress forces and losses

5.5.1    Short-term losses

5.5.2    Long-term losses

5.6       Secondary effects

5.7       Analysis of flat slabs

5.7.1    General

5.7.2    Equivalent frame analysis

5.7.3    Finite element or grillage analysis

5.7.4    Analysis for the load case at transfer of prestress

5.7.5    Analysis for non-uniform loads

5.8       Flexural section design

5.8.1    Serviceability Limit State: stresses after losses

5.8.2    Serviceability Limit State: stresses at transfer

5.8.3    Crack width control

5.8.4    Deflection control

5.8.5    Ultimate Limit State

5.8.6    Progressive collapse

5.8.7    Designed flexural un-tensioned reinforcement

5.8.8    Minimum un-tensioned reinforcement

5.9       Shear strength

5.9.1    General

5.9.2    Beams and one-way spanning slabs

5.9.3    Flat slabs (punching shear)

5.9.4    Structural steel shearheads

5.10     Openings in slabs

5.11     Anchorage bursting reinforcement

5.11.1  Serviceability limit state (SLS)

5.11.2  Ultimate limit state (ULS)

5.12     Reinforcement between tendon anchorages

5.13     Vibration

5.14     Lightweight aggregate concrete

6          DETAILING

6.1       Cover to reinforcement

6.1.1    Bonded tendons

6.1.2    Unbonded tendons

6.1.3    Un-tensioned reinforcement

6.1.4    Anchorages

6.2       Tendon distribution

6.3       Tendon spacing

6.4       Tendon notation

6.5       Tendon supports

6.6       Layout of un-tensioned reinforcement

6.6.1    At columns

6.6.2    Shear reinforcement

6.6.3    At and between anchorages

6.7       Penetrations and openings in floors

7          CONSTRUCTION DETAILS

7.1       Supply and installation of post-tensioning systems

7.2       Extent of pours

7.3       Construction joints

7.4       Protection of anchorages

7.5       Back-propping

7.6       Stressing procedure

7.7       Grouting

7.8       Soffit marking

8          DEMOLITION

8.1       General

8.2       Structures with bonded tendons

8.3       Structures with unbonded tendons

9          SPECIAL USES OF POST-TENSIONING IN BUILDING STRUCTURES

9.1       General

9.2       Transfer structures

9.3       Foundation structures

9.4       Ground slabs

10        REFERENCES

APPENDICES

A Examples of calculations

A.1 Solid flat slab with unbonded tendons

A.1.1 Description, properties and loads

A.1.2 Serviceability Limit State – Transverse direction

A.1.3 Loss calculations

A.2 Finite element design example

A.2.1 Description, properties and loads

A.2.2 Analysis

A.2.3 Results from analysis

A.2.4 Reinforcement areas

A.2.5 Deflection checks

A.3 Punching shear design for Example Al

A.3.1 Properties

A.3.2 Applied shear

A.3.3 Shear resistance

A.3.4 Shear reinforcement

B Calculation of prestress losses

B.l       Friction losses in the tendon

B.2      Wedge set or draw-in

B.3      Elastic shortening of the structure

B.4      Shrinkage of the concrete

B.5      Creep of concrete

B.6      Relaxation of the tendons

C         Calculation of tendon geometry

D         Calculation of secondary effects using equivalent loads

E Calculation and detailing of anchorage bursting reinforcement

E.1 Bursting reinforcement for Example Al

E.2 Bursting reinforcement for broad beam

F  Simplified shear check – derivation of Figures 19 and 20

G  Vibration serviceability of post-tensioned concrete floors

G.1 Introduction

G.2      Principles of floor vibration  analysis

G.3      Walking excitation

G.3.1 Dynamic load factors   for resonant

response calculations

G.3.2 Effective impulses for transient response calculations

G.4      Response of low-frequency floors

G.5      Response of high-frequency floors

G.6 Modelling of mass, stiffness and damping of post-tensioned concrete floors

G.7 Assessment of vibration levels

G.7.1 Human reaction based on RMS accelerations

G.7.2 Human reaction based on vibration dose value

G.7.3 Effect of vibration on sensitive equipment

H Effect of early thermal shrinkage on a structural frame with prestressed beams