445.1R-12 Report on Torsion in Structural Concrete

445.1R-12 Report on Torsion in Structural Concrete

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Description

A clear understanding of the effects of torsion on concrete members is essential to the safe, economical design of reinforced and prestressed concrete members. This report begins with a brief and systematic summary of the 180-year history of torsion of structural concrete members, new and updated theories and their applications, and a historical overview outlining the development of research on torsion of structural concrete members. Historical theories and truss models include classical theories of Navier, Saint-Venant, and Bredt; the three-dimensional (3-D) space truss of Rausch; the equilibrium (plasticity) truss model of Nielson as well as Lampert and Thürlimann; the compression field theory (CFT) by Collins and Mitchell; and the softened truss model (STM) by Hsu and Mo.

This report emphasizes that it is essential to the analysis of torsion in reinforced concrete that members should: 1) satisfy the equilibrium condition (Mohr’s stress circle); 2) obey the compatibility condition (Mohr’s strain circle); and 3) establish the constitutive relationships of materials such as the “softened” stress-strain relationship of concrete and “smeared” stress-strain relationship of steel bars. The behavior of members subjected to torsion combined with bending moment, axial load, and shear is discussed. This report deals with design issues, including compatibility torsion, spandrel beams, torsional limit design, open sections, and size effects.

The final two chapters are devoted to the detailing requirements of transverse and longitudinal reinforcement in torsional members with detailed, step-by-step design examples for two beams under torsion using ACI (ACI 318-11), European (EC2-04), and Canadian Standards Association (CSA-A23.3-04) standards. Two design examples are given to illustrate the steps involved in torsion design. Design Example 1 is a rectangular reinforced concrete beam under pure torsion, and Design Example 2 is a prestressed concrete girder under combined torsion, shear, and flexure.

Keywords: combined action (loading); compatibility torsion; compression field theory; equilibrium torsion; interaction diagrams; prestressed concrete; reinforced concrete; shear flow zone; skew bending; softened truss model; spandrel beams; struts; torsion detailing; torsion redistribution; warping.

 

Document Details

Author: Joint ACI-ASCE Committee 445

Publication Year: 2013

Pages: 92.00

ISBN: 9780870318108

Categories: Torsion

Formats: PDF, ePub, or Kindle

Table of Contents

CHAPTER 1—INTRODUCTION AND SCOPE

1.1—Introduction

1.2—Scope

CHAPTER 2—NOTATION AND DEFINITIONS

2.1—Notation

2.2—Definitions

CHAPTER 3—HISTORICAL OVERVIEW OF TORSION THEORIES AND THEORETICAL MODELS

3.1—Navier’s theory

3.2—Thin-tube theory

3.3—Historical development of theories for reinforced concrete members subjected to torsion

3.4—Concluding remarks

CHAPTER 4—BEHAVIOR OF MEMBERS SUBJECTED TO PURE TORSION

4.1—General

4.2—Plain concrete

4.3—Reinforced concrete

4.4—Prestressed concrete

4.5—High-strength concrete

4.6—Concluding remarks

CHAPTER 5—ANALYTICAL MODELS FOR PURE TORSION

5.1—General

5.2—Equilibrium conditions

5.3—Compatibility conditions

5.4—Stress strain relationships

5.5—Compression field theory

5.6—Softened truss model

5.7—Graphical methods

CHAPTER 6—MEMBERS SUBJECTED TO TORSION COMBINED WITH OTHER ACTIONS

6.1—General

6.2—Torsion and flexure

6.3—Torsion and shear

6.4—Torsion and axial load

6.5—Torsion, shear, and flexure

CHAPTER 7—ADDITIONAL DESIGN ISSUES RELATED TO TORSION

7.1—General

7.2—Compatibility torsion and torsional moment redistribution

7.3—Precast spandrel beams

7.4—Torsion limit design

7.5—Treatment of open sections

7.6—Size effect on the strength of concrete beams in torsion

CHAPTER 8—DETAILING FOR TORSIONAL MEMBERS

8.1—General

8.2—Transverse reinforcement

8.3—Longitudinal reinforcement

8.4—Detailing at supports

CHAPTER 9—DESIGN EXAMPLES

9.1—Torsion design philosophy

9.2—Torsion design procedures

9.3—Introduction to design examples

9.4—Design Example 1: solid rectangular reinforced concrete beam under pure torsion

9.5—Design Example 2: Prestressed concrete box girder under combined torsion, shear, and flexure

CHAPTER 10—REFERENCES

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