ACI PRC-445.2-21: Strut-and-Tie Method Guidelines for ACI 318-19 - Guide

Description

Strut-and-tie models (STMs) were first used at the end of the nineteenth century as a concrete design method. The method was added to ACI 318 in 2002 as Appendix A. In 2014, STM provisions were moved into the main body of the code as Chapter 23, Strut-and-Tie Method. This document focuses on the ACI 318-19 implementation of strut-and-tie modeling. The main objectives of this document are to: 1) explain the intent and application of ACI 318 STM provisions; 2) provide additional design guidance for the STM based on other design codes, specifications, and committee documents; and 3) present design recommendations from recent research publications. This document provides practical guidance to the structural design community.

Keywords:

D-regions; design; disturbed regions; model; node; strut; tie.

Document Details

Author: Joint ACI-ASCE Committee 445

Publication Year: 2021

Pages: 88

ISBN: 9781641951463

Formats: Printed Document or Protected PDF/Web View

Table of Contents

CHAPTER 1—INTRODUCTION, p. 2

1.1—Background, p. 2

1.2—Objectives, p. 2

CHAPTER 2—NOTATION AND DEFINITIONS, p. 2

2.1—Notation, p. 2

2.2—Definitions, p. 4

CHAPTER 3—OVERVIEW OF THE STRUT-AND-TIE MODEL DESIGN PROCEDURE, p. 5

3.1—Introduction, p. 5

3.2—Overview of the strut-and-tie method, p. 5

3.3—Conceptual example, p. 6

3.4—Historical development of the strut-and-tie method, p. 9

CHAPTER 4—DESIGN STRENGTH OF STRUTS, TIES, AND NODES, p. 10

4.1—Overview, p. 10

4.2—Strut and node types and factors influencing strength, p. 11

4.3—STM strength requirements, p. 14

4.4—Strength and requirements for struts, p. 14

4.5—Strength and requirements for ties, p. 17

4.6—Strength and requirements for nodes, p. 19

CHAPTER 5—MODELING AND DESIGN CONSIDERATIONS, p. 23

5.1—Introduction, p. 23

5.2—Influence of model topology on performance of complex D-regions, p. 23

5.3—Guidance to selection of STM shapes, p. 25

5.4—Calculating member forces and stresses in complex D-regions, p. 28

5.5—Comparison of sectional and STM design of transverse reinforcement in a B-region, p. 30

5.6—Refined models for cracking of struts and the size effect, p. 31

5.7—States of stress in nodes, p. 32

5.8—Maximum shear stress limits in beams, p. 34

5.9—Member dimensions and constitutive relationships, p. 36

5.10—Reinforcement arrangement in relation to tie orientation, p. 37

5.11—Consideration of prestressing, p. 37

5.12—Capacity evaluation of existing structures, p. 39

5.13—Computer-based design aids, p. 40

CHAPTER 6—SERVICEABILITY CONSIDERATIONS, p. 41

6.1—Introduction, p. 41

6.2—Cracking at service limit states, p. 41

6.3—Determination of required distributed reinforcement, p. 42

6.4—Distributed reinforcement placement and detailing, p. 42

6.5—Deflections, p. 43

CHAPTER 7—IMPLEMENTATION OF STM DESIGN AND CONSTRUCTION DETAILS, p. 44

7.1—Introduction, p. 44

7.2—Deep beams, p. 44

7.3—Frame corners and beam-column joints, p. 46

7.4—Corbels, p. 48

7.5 Dapped-end beams, p. 50

7.6—Beams supporting beams (indirect supports), p. 53

7.7—Inverted T-beams, p. 56

7.8—Walls and beams with openings, p. 58

7.9—Coupling beams, p. 60

7.10—Footings, p. 62

7.11—Pile caps, p. 62

7.12—Post-tensioned anchorage zones, p. 64

CHAPTER 8—OTHER STM DESIGN SPECIFICATIONS, CODES, AND GUIDE DOCUMENTS, p. 66

8.1—Introduction, p. 66

8.2—Strut-and-tie design requirements in CSA A23.3-19, p. 66

8.3 American Association of State Highway and Transportation Officials (AASHTO), p. 69

8.4—FIP Recommendations (FIP 1999), p. 71

8.5—Eurocode 2, p. 74

8.6—fib Model Code for Concrete Structures 2010 (fib 2013), p. 75

CHAPTER 9—REFERENCES, p. 75

9.1—Referenced standards and reports, p. 76

9.2—Authored references, p. 76

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