An ACI Manual

Formwork for Concrete

8th Edition

SP-4 (14)
FORMWORK FOR CONCRETE
FORMWORK FOR
CONCRETE
Eighth Edition

DAVID W. JOHNSTON
Edward I. Weisiger Distinguished Professor Emeritus
North Carolina State University

Prepared with the assistance of

ACI COMMITTEE 347, FORMWORK FOR CONCRETE

Kenneth L. Berndt, Chair N. John Gardner Robert G. McCracken

Matthew J. Poisel, Secretary Brian J. Golanowski Eric S. Peterson
Timothy Hayes Steffen Pippig
Rodney D. Adams G. P. Jum Horst Douglas J. Schoonover
Mary Bordner-Tanck Jeffrey C. Jack Aviad Shapira
George Charitou David W. Johnston John M. Simpson
Eamonn F. Connolly Roger S. Johnston Rolf A. Spahr
James N. Cornell II Robert G. Kent Pericles C. Stivaros
Jack L. David Kevin R. Koogle Daniel B. Toon
Aubrey L. Dunham Jim Kretz Ralph H. Tulis
Jeffrey C. Erson H. S. Lew
Formwork for Concrete

8th Edition

First Printing: August 2014

Second Printing: December 2014
Third Printing: January 2016
Fourth Printing: February 2017
Fifth Printing: January 2018
Sixth Printing: September 2018

Errata changes as of October 31, 2019

Printed in Chelsea, Michigan

ISBN 978-0-87031-912-9
Copyright © 2014 by the American Concrete Institute.
All rights reserved.

This eighth edition has been revised to agree with “Guide to Formwork for Concrete (ACI
347R-14),” which is reprinted in full in the appendix. Other revisions have been made
for consistency with ACI documents undergoing revision since previous editions of this
manual were issued. Wood design stresses and procedures have been updated to agree
with the 2012 National Design Specification® issued by the American Wood Council. ”

The drawings and examples in this book are based on typical designs and should not be
used as working drawings or in place of making calculations for a particular project. They
are intended to be helpful in the preparation of complete formwork plans that should be
adapted to local conditions and comply with all applicable legal requirements. In no way
is this book able to, or intended to, supplant the qualified designer or engineer to whom
formwork should be entrusted.

Limitations of space and time make it impossible to show all of the methods, materials,
and products available for formwork construction. Omission of any item therefore should
not be regarded as a judgment that it is inferior or unsuitable.

Managing Editor:  Michael Tholen, Ph.D., P.E.

Art Program:  Claire Hiltz
Manager, Publishing Services:  Barry Bergin
Production Editors:  Carl Bischof, Kelli Slayden, Ashley Poirier, Kaitlyn Hinman
Page Design & Composition:  Ryan Jay
Cover, Acknowledgements, and Foreword art courtesy Eric Peterson
Manufacturing:  Marie Fuller

American Concrete Institute

38800 Country Club Drive
Farmington Hills, MI 48331
USA
www.concrete.org
DEDICATION
The eighth edition of Formwork for Concrete is dedicated to the memory and achieve-
ments of M. K. Hurd, author of the first seven editions and constant advocate for safety,
economy, and quality of formwork. Mary Hurd (1926-2013), a civil engineering graduate
of Iowa State University, began her career as a staff engineer with the American Concrete
Institute in 1947. In the early 1960s, she was asked by ACI to work with the committee
on Formwork for Concrete to develop a major publication on formwork that had been
identified as an industry need. Over the years, as she moved at various times from ACI
staff engineer to private consultant or editor of concrete industry publications, she was
repeatedly engaged by ACI to update Formwork for Concrete. Well known and respected
as an engineering writer and editor on concrete construction, formwork, and concrete
aesthetics, she published over 230 articles on always-timely topics.
In the five decades since Formwork for Concrete made its first appearance, more than
130,000 copies have been printed and the book has become recognized as the “green
bible” of the formwork industry. Formwork for Concrete has been and continues to be a
cooperative effort supported by individuals, companies, public agencies, and industry
and professional associations in large measure due to the groundwork laid and respect for
Formwork for Concrete garnered through the pioneering efforts of Mary Hurd.

Mary K. Hurd in 1969

v
 ACKNOWLEDGMENTS
The American Concrete Institute would like to acknowledge the hard work and support
of several groups and individuals without whom the production of a document of this
caliber would not be possible.
Without the vision and effort put forth by Mary K. Hurd and the members of ACI
Committee 347 over the last 50 years, much of the basis for this document would not exist.
Their work has established Formwork for Concrete as a well-known and respected reference
in the concrete formwork industry and as an excellent teaching resource in classrooms
across the United States.
David W. Johnston, Ph.D., P.E., took on the task of revising and bringing an iconic docu-
ment up-to-date by including the latest design standards, design methods, procedures,
products, and several new worked examples. In addition, he coordinated the selection
of nearly 500 modern color photographs to enable the eighth edition of Formwork for
Concrete to be the first edition in full color. Photos in this manual without photo credit
were provided by Dr. Johnston. The assistance of Matthew Poisel in revising the document
is also gratefully acknowledged.
The assistance of the many formwork and construction companies that permitted the
use of their photographs and illustrations allows Formwork for Concrete to show a breadth
of formwork application that would not be possible otherwise. Specific acknowledgments
for their contributions are found in the figure captions.
Members of ACI Committee 347, Formwork for Concrete, were engaged by the author
during the process of revising the document, as they have been during the development
of previous editions. Their comments and insight have brought a balanced viewpoint to
the document that is not found in other documents on the topic.
Members of the ACI Educational Activities Committee (EAC), with the assistance of
outside reviewers selected from ACI Committee 347, provided final review comments for
chapters of the document. Responses by the author to these comments were reviewed
and approved by the EAC members who commented on the chapter. These comments
provided a fresh perspective and helped ensure that people reading the document for the
first time would be able to quickly and easily understand the content. These reviewers also
made sure that the content of this work
was consistent with other ACI documents.
These suggestions have helped improve
the document for the final end user.

Michael Tholen, Ph.D., P.E.

Managing Editor

vi
FOREWORD
Following in the footsteps of Mary K. Hurd is a challenge. My respect for her knowledge
of formwork included recent decades of interaction with her on ACI Committee 347, but
also extended back to my days as a student specializing in construction engineering and
structural engineering. In 1965, I encountered the first edition of Formwork for Concrete
as a construction engineering undergraduate student at North Carolina State Univer-
sity. During my years in industry and later as a faculty member, my appreciation of her
pioneering and dedicated work on Formwork for Concrete and her contributions to ACI
Committee 347 continued to grow.
The eighth edition, as all previous editions, follows the most recent guidelines estab-
lished by ACI Committee 347 and documented in the committee report, now ACI 347R-
14, which is reprinted in full in the appendix. This new edition of Formwork for Concrete
considers the updated lateral pressure provisions now provided by ACI 347. Expanded
coverage is provided for wind loads, analysis of the shoring and reshoring process,
evaluation of concrete and structure strength to withstand shoring loads, and design of
shoring and bracing elements. This edition also reflects the latest changes in wood design
recommendations of the American Wood Council and introduces LRFD in addition to the
primary coverage based on ASD procedures. The recent recommendations of other ACI
committees have also been considered in the manual revisions and some related provi-
sions of ACI 318 and OSHA have been extracted for convenient reference in the appendix.
The growing number of standards related to design of the construction process and
design of temporary structures, as well as a number of formwork industry products and
practices adopted since the last edition was published, have been considered during
development of the revisions. For instructional use, a series of problems and review ques-
tions have been provided following the appendix.
Drafts of revisions have been submitted for review and comment by members of ACI
Committee 347, whose suggestions and advice have been most constructive. I am very
grateful to the many committee members who shared their expertise and counsel during
the preparation of the eighth edition. My special thanks to colleague Matthew Poisel, for
his development of the data for the span tables of Chapter 9. The author is also grateful
to the many individuals and organizations who have contributed nearly 500 new illustra-
tions, drawings, and photo images to this first edition to be printed in color and to the
many contractors who have provided access to their construction sites for photographs by
the author, particularly United Forming, Inc., and Clancy & Theys Construction Co.

David W. Johnston, Ph.D., P.E.

July 2014

vii
 Chapters
1: INTRODUCTION

2: GENERAL OBJECTIVES IN FORMWORK BUILDING

3: OVERALL PLANNING

4: MATERIALS, ACCESSORIES, AND PROPRIETARY PRODUCTS

5: LOADS AND PRESSURES

6: SHORING AND FLOOR LOADS IN MULTI-STORY

STRUCTURES

7: DESIGN OF SLAB, WALL, BEAM, AND COLUMN FORMS

8: DESIGN OF FORM SHORES AND BRACING

9: DESIGN TABLES

10: FORMWORK DRAWINGS

11: BUILDING AND ERECTING THE FORMWORK

12: USING THE FORMS

13: FORMED CONCRETE SURFACE QUALITY

14: FORMWORK FOR ARCHITECTURAL CONCRETE

15: BRIDGE FORMWORK

16: MASS CONCRETE FORMWORK

17: TUNNEL AND SHAFT FORMWORK

18: SPECIAL TECHNIQUES IN CONCRETE CONSTRUCTION

APPENDIX A—REFERENCED STANDARDS AND REPORTS

APPENDIX B—NOTATION

APPENDIX C—GLOSSARY

APPENDIX D—CONVERSIONS

APPENDIX E—ACI 347R-14 GUIDE

APPENDIX F—ACI 318-11 CODE AND COMMENTARY

APPENDIX G—OSHA REGULATIONS

APPENDIX H—PROBLEMS

INDEX

viii
CONTENTS
1: INTRODUCTION

2: GENERAL OBJECTIVES IN FORMWORK BUILDING

2.1 Standards, Specifications, and Guides Related to Formwork 2-1
2.1.1 Regulations for Safety 2-1
2.1.2 Project Specifications for Quality 2-2
2.1.3 Guides and Specifications for Formwork Design and Construction 2-2

2.2 How Formwork Affects Concrete Quality 2-3

2.3 Planning for Safety 2-3
2.3.1 Supervision and Inspection 2-3
2.3.2 Platforms and Access for Workers 2-3
2.3.3 Control of Concreting Practices 2-4
2.3.4 Improving Soil Bearing and Bracing 2-4
2.3.5 Shoring and Reshoring 2-4

2.4 Causes of Failures 2-5

2.4.1 Improper Stripping and Shore Removal 2-5
2.4.2 Inadequate Bracing 2-6
2.4.3 Inadequate Concrete Strength Development 2-6
2.4.4 Vibration and Impact 2-6
2.4.5 Unstable Soil under Mudsills, Shoring Not Plumb 2-8
2.4.6 Inadequate Control of Concrete Placement 2-8
2.4.7 When Formwork Is Not at Fault 2-8
2.4.8 Lack of Attention to Formwork Details 2-10

2.5 Relationship of Architect, Engineer, and Contractor 2-10

2.5.1 Defining the Concrete Structure 2-10
2.5.2 Maintaining and Coordinating Tolerances 2-11
2.5.3 Preparing a Formwork Specification 2-11
2.5.4 Design, Inspection, and Approval of Formwork 2-12
2.5.5 Complex Structures 2-12
2.5.6 Stay-in-Place Forms 2-12
2.5.7 Composite Construction 2-12
2.5.8 Stripping and Decentering 2-12
2.5.9 Materials and Accessories Related to Formed Surface of Exposed Concrete 2-13

2.6 Achieving Economy of Formwork 2-13

2.6.1 Measurement and Payment for Formwork 2-14
2.6.2 How the Engineer/Architect Can Reduce Form Costs 2-14

3: OVERALL PLANNING
3.1 Development of a Basic System 3-1
3.1.1 Compare Alternate Methods 3-2
3.1.2 Examine Form Plan in Relation to Total Job 3-2

3.2 Key Areas of Cost Reduction 3-2

3.3 Planning for Maximum Reuse 3-3
3.3.1 Developing a Practical Reuse Plan 3-4
3.3.2 Comparing Reuse Schemes 3-4

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 3.4 Economical Form Construction 3-4
3.4.1 Job-Built Forms 3-4
3.4.2 Purchased or Rented Forms 3-6

3.5 Setting, Stripping, and Cycling Costs 3-6

3.6 Other Costs Affected by the Formwork Plan 3-7
3.6.1 Crew Efficiency 3-7
3.6.2 Cranes and Hoists 3-8

3.7 Formwork Planning Process 3-8

3.8 BIM for Planning Formwork Operations 3-13
3.8.1 How BIM is Used by a Formwork Contractor 3-13
3.8.2 Advantages of BIM 3-15

4: MATERIALS, ACCESSORIES, AND PROPRIETARY PRODUCTS

4.1 Lumber 4-1
4.1.1 Kinds of Lumber 4-2
4.1.2 Lumber Finish and Sizes 4-3
4.1.3 Stress Grading and Design Values 4-4
4.1.4 Adjustment Factors for Sawn Lumber Design Values 4-6

4.2 Engineered Wood Products 4-8

4.2.1 Glued Laminated Timber 4-9
4.2.2 Structural Composite Lumber 4-10
4.2.3 I-Joists 4-11
4.2.4 Wood Trusses 4-11

4.3 Plywood 4-11

4.3.1 Construction and Sizes Available 4-12
4.3.2 Types and Grades 4-12
4.3.3 Overlaid Plywood 4-14
4.3.4 Textured Surfaces 4-15
4.3.5 Strength Properties 4-15
4.3.6 Bending Plywood to Curved Surfaces 4-15

4.4 Other Framing and Facing Materials 4-16

4.4.1 Reconstituted Wood Materials 4-16
4.4.2 Steel 4-16
4.4.3 Aluminum 4-17
4.4.4 Glass Fiber-Reinforced Polymer 4-18
4.4.5 Other Polymeric Form Materials 4-18
4.4.6 Fabric and Porous Forms 4-19
4.4.7 Form Lining Materials 4-20
4.4.8 Insulation and Insulating Forms 4-22

4.5 Hardware and Fasteners 4-23

4.5.1 Nails 4-23
4.5.2 Wood Screws 4-26
4.5.3 Bolts, Lag Screws, and Other Connectors 4-28
4.5.4 Ties 4-31
4.5.5 Anchors 4-35
4.5.6 Hangers 4-36
4.5.7 Friction Collars and Support Brackets 4-36

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 4.5.8 Spacers and Spreaders 4-37
4.5.9 Steel Strapping 4-37
4.5.10 Column Clamps 4-38

4.6 Prefabricated Forms 4-38

4.6.1 Panel Forms and Forming Systems 4-38
4.6.2 Pans and Domes for Concrete Joist Construction 4-39
4.6.3 Void and Duct Forms 4-40
4.6.4 Column Forms 4-41
4.6.5 Stay-In-Place Forms 4-42
4.6.6 Special Purpose and Custom-Made Forms 4-43

4.7 Shoring 4-43

4.7.1 Single-Post Shores 4-44
4.7.2 Shoring Frames 4-44

5: LOADS AND PRESSURES

5.1 Notation for Loads and Pressures 5-1
5.2 Load Combinations 5-2
5.2.1 ASD Combinations 5-2
5.2.2 LRFD Combinations 5-2

5.3 Vertical Loads 5-3

5.3.1 Dead Loads 5-3
5.3.2 Live Loads 5-4

5.4 Lateral Pressure of Fresh Concrete 5-4

5.4.1 Factors Affecting Lateral Pressure 5-6
5.4.2 History of Lateral Pressure Values for Form Design 5-7
5.4.3 Lateral pressure of concrete equations 5-8
5.4.4 Bottom-Up Pumping of Concrete 5-9
5.4.5 Column Forms 5-10
5.4.6 Wall Forms 5-10
5.4.7 Pressure on Sloping Surfaces 5-11

5.5 Horizontal Loads 5-13

5.5.1 Minimum Horizontal Loads 5-13
5.5.2 Wind Loads 5-14
5.5.3 Shielding from Wind Pressure 5-17
5.5.4 Design Wind Load 5-18
5.5.5 Wind Load on Wall and Column Forms 5-18
5.5.6 Wind Loads on Elevated Slab Formwork 5-19
5.5.7 Starting and Stopping Equipment Loads 5-20
5.5.8 Seismic Loads 5-20

5.6 Other Loads 5-20

6: SHORING AND FLOOR LOADS IN MULTI-STORY

STRUCTURES
6.1 Shoring of Multi-story Concrete Structures during Construction 6-1
6.2 Shoring and Reshoring Loads in Multi-story Structures 6-3
6.2.1 Analyzing the Loads 6-3
6.2.2 Comparison of Example Analysis Results 6-5

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 6.3 Backshoring 6-16
6.4 Drophead Shores 6-16
6.5 LRFD Analysis 6-17
6.6 Shoring System Design 6-21
6.7 Determining Concrete Strength for Stripping and Loading for Cycle Times 6-22
6.7.1 Analysis and Design Process for Slab Strength 6-22
6.7.2 Alternative Load Distributions 6-26
6.7.3 More Concentrated Shore Loads 6-26
6.7.4 Structures Designed for Composite Action 6-26
6.7.5 Post-Tensioned Structures 6-27

6.8 Effect of Early Loading on Slab Deflection 6-27

6.9 Monitoring Early Strength Gain of Concrete in the Field 6-27
6.9.1 Field-Cured Cylinders 6-27
6.9.2 Alternate Tests 6-27

7: DESIGN OF SLAB, WALL, BEAM, AND COLUMN FORMS

7.1 Notation 7-2
7.2 Basic Simplifications 7-3
7.3 Beam Formulas 7-4
7.4 Design Criteria for Wood Beams 7-7
7.4.1 Stresses and Deformations 7-7
7.4.2 Bending 7-7
7.4.3 Deflection 7-9
7.4.4 Shear 7-10
7.4.5 Bearing 7-13

7.5 Form Design 7-13

7.6 Wall Form Design 7-15
7.7 Slab Form Design 7-22
7.8 Beam Form Design 7-27
7.9 Column Form Design 7-30
7.9.1 Types of Column Forms 7-31
7.9.2 General Design Procedure 7-31

7.10 Form Accessories 7-33

7.10.1 Ties 7-36
7.10.2 Bearing Plates or Washers 7-37
7.10.3 Hangers 7-37

8: DESIGN OF FORM SHORES AND BRACING

8.1 Shoring and Bracing Members 8-1
8.2 Solid Wood Compression Members 8-2
8.3 Tubular Steel Shores 8-5
8.3.1 Slenderness Ratio 8-5
8.3.2 Compression Strength 8-5
8.3.3 Steel Shoring Frames 8-6

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 8.4 Other Manufactured Shoring Devices 8-7
8.5 Support for Shoring 8-8
8.6 Bracing for Lateral Loads 8-8
8.6.1 Wall Form Bracing Loads 8-8
8.6.2 Design of Braces 8-9
8.6.3 Bracing of Slab Forms Supported by Individual Shores 8-9
8.6.4 Design of Wood Bracing Connections 8-10

8.7 Camber and Adjustment for Settlement 8-10

8.7.1 Anticipated Deflection or Settlement of Formwork 8-10
8.7.2 Deflection of the Finished Structure 8-13
8.7.3 Total Allowance for Camber and Adjustments 8-13

8.8 Anchorage of braces 8-13

8.8.1 Deadmen 8-13
8.8.2 Concrete anchors 8-14
8.8.3 Ground anchors 8-14
8.8.4 Anchors 8-14

9: DESIGN TABLES
9.1 Equations for Calculating Safe Span 9-1
9.2 Sheathing Design: Tables 9.3 to 9.5 9-4
9.3 Joists, Studs, and Beams: Tables 9.6 to 9.8 9-4
9.4 Double Members: Tables 9.9 to 9.11 9-5
9.5 Wood Shores: Tables 9.12 and 9.13 9-5
9.6 Form Design Using the Tables 9-7

10: FORMWORK DRAWINGS

10.1 Preparing Effective Drawings 10-1
10.2 Line Drawings 10-2
10.3 General Layout and Detail Drawings 10-3
10.4 Checklist of Details 10-13
10.5 Recheck for Agreement with Structural Drawings 10-16
10.6 Drawing Review 10-16
10.7 BIM 3-D Graphical Views of Formwork 10-17

11: BUILDING AND ERECTING THE FORMWORK

11.1 Form Fabrication 11-2
11.1.1 Location of Shop at Project Site 11-2
11.1.2 Storage of Materials and Finished Parts 11-3
11.1.3 Equipment and Layout 11-3

11.2 Formwork Erection Safety 11-4

11.3 Footings 11-5
11.3.1 Wall Footings 11-5
11.3.2 Column Footings 11-6

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 11.4 Slab-on-Ground and Paving Work 11-7
11.4.1 Slabs-on-Ground 11-7
11.4.2 Highway and Airport Paving 11-8
11.4.3 Curb and Gutter Forms 11-9

11.5 Wall Forms 11-9

11.5.1 Job-Built Forms 11-9
11.5.2 Prefabricated Panel Systems 11-12
11.5.3 Ganged Panel Forms and Climbing Forms 11-12
11.5.4 Blind Side and Single-Side Wall Forming 11-14
11.5.5 Square Corners 11-14
11.5.6 Pilasters 11-14
11.5.7 Curved Walls and Round Corners 11-15
11.5.8 Wall Openings 11-17
11.5.9 Joints 11-17
11.5.10 Forms for External Vibration 11-18
11.5.11 ACI Tolerances for Walls 11-19

11.6 Column Forms 11-19

11.6.1 Erection Practices 11-19
11.6.2 Square or Rectangular Columns 11-21
11.6.3 Round and Flared Columns 11-21
11.6.4 Column Heads 11-22
11.6.5 ACI Column Tolerances 11-24

11.7 Beam or Girder Forms 11-24

11.7.1 Beam Bottoms 11-24
11.7.2 Beam Sides 11-25
11.7.3 Panel Assembly and Erection 11-26
11.7.4 Suspended Forms for Fireproofing and Composite Construction 11-27
11.7.5 Beam and Girder Tolerances 11-28

11.8 Slab Forms 11-28

11.8.1 Beam and Slab Construction 11-28
11.8.2 Flat Plates and Flat Slabs 11-29
11.8.3 Concrete Joist Construction 11-30
11.8.4 Flying Form Systems 11-32
11.8.5 Adjustable Steel Beams 11-33
11.8.6 Slabs Supported on Steel Beams or Precast Concrete Beams 11-34
11.8.7 Metal Decking 11-34
11.8.8 ACI Tolerances for Slab Work 11-34

11.9 Shoring 11-35

11.9.1 Shore Layout and Installation 11-35
11.9.2 Mudsills or Shoring Foundations 11-37
11.9.3 Wood Shores 11-37
11.9.4 Adjustable Shores 11-37
11.9.5 Drophead Shore Systems 11-38
11.9.6 Shoring Towers 11-38
11.9.7 Adjustment and Jacking 11-39
11.9.8 Permanent Shores and Back Shores 11-39
11.9.9 Composite Construction 11-40

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12: USING THE FORMS
12.1 Placing Reinforcement and Inserts 12-2
12.1.1 Support for Reinforcing Bars 12-3
12.1.2 Positioning Bars; Placement Tolerances 12-4

12.2 Preparation for Concreting 12-5

12.2.1 Form Release Agents 12-5
12.2.2 Sticking and Staining Problems 12-7
12.2.3 Use of Water on the Forms 12-8

12.3 Inspection and Form Watching 12-8

12.3.1 Before Concreting 12-9
12.3.2 During and After Concreting 12-11

12.4 Placing and Vibrating—Effect on Formwork 12-11

12.5 Removal of Forms and Shores 12-12
12.5.1 Stripping Time Based on Concrete Strength 12-12
12.5.2 Form Removal Related to Curing Needs 12-14
12.5.3 Stripping Techniques 12-14
12.5.4 Multi-Story Buildings 12-16

12.6 Reshoring 12-16

12.7 Care and Storage of Forms and Accessories 12-18
12.8 Cold Weather Protection 12-19
12.8.1 Form Insulation and Heating 12-20
12.8.2 Avoiding Thermal Shock 12-23

13: FORMED CONCRETE SURFACE QUALITY

13.1 Overview of ACI 301 Formed Surface Provisions 13-1
13.1.1 General Requirements 13-2
13.1.2 As-Cast Surface Finishes 13-3
13.1.3 Rubbed Surface Finishes 13-3

13.2 Overview of ACI 347.3R Formed Concrete Surface Provisions 13-3

13.2.1 Determination of Surface Void Ratio 13-4
13.2.2 Specifications 13-5
13.2.3 Design Considerations 13-6
13.2.4 Construction 13-8
13.2.5 Evaluation of formed concrete surfaces and repair procedures 13-10

14: FORMWORK FOR ARCHITECTURAL CONCRETE

14.1 Specifications: Defining Quality 14-2
14.2 Architectural Formwork Design 14-3
14.2.1 Loads and Pressures 14-3
14.2.2 Design Standards 14-4
14.2.3 Formwork Details 14-5

14.3 Exposed Concrete Surfaces 14-5

14.3.1 Smooth As-Cast Surfaces 14-6
14.3.2 Textured As-Cast Surfaces 14-8
14.3.3 Precast Panels as Forms or Liners 14-10

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 14.4 Construction of Forms for Architectural Concrete 14-12
14.4.1 Walls 14-12
14.4.2 Columns and Pilasters 14-15
14.4.3 Spandrels and Parapets 14-16
14.4.4 Soffits 14-17
14.4.5 Cantilevers 14-17
14.4.6 Ornamental Detail 14-18
14.4.7 Erection Practices 14-21
14.4.8 Construction and Contraction Joints 14-23

14.5 Stripping 14-24

14.6 Cleanup and Repair 14-25

15: BRIDGE FORMWORK

15.1 Foundations 15-2
15.1.1 Caissons 15-2
15.1.2 Piles 15-4
15.1.3 Rock or Soil Offering Direct Support 15-4

15.2 Piers 15-5

15.2.1 Forms Moved for Reuse 15-5
15.2.2 Round Piers 15-6
15.2.3 Stonework Facing 15-6
15.2.4 Massive Piers 15-6
15.2.5 Vertical Alignment 15-6
15.2.6 Access for Workers 15-7
15.2.7 External Ties 15-7
15.2.8 Pier Caps and Tie Struts 15-7

15.3 Superstructures 15-8

15.3.1 Monolithic—Simple Slab, Beam, and Girder 15-8
15.3.2 Cast-in-Place Deck Supported on Steel or Precast Girders 15-9
15.3.3 Expansion Joints 15-10
15.3.4 Overhang, Sidewalks, Parapets, and Median Barriers 15-10
15.3.5 Support for Superstructure Forms 15-10
15.3.6 Stripping Bridge Forms 15-11

15.4 Arch Bridges 15-12

15.5 Segmental Box-Girder Bridge Construction 15-12
15.5.1 Cast-in-Place Segmental Construction 15-13
15.5.2 Precast Segmental Construction 15-13
15.5.3 Principal Erection Methods 15-14
15.5.4 Making Precast Bridge Segments 15-17
15.5.5 Voids, Inserts, Attachments 15-19
15.5.6 Joint Surfaces 15-19
15.5.7 Vibration 15-19
15.5.8 Heat Curing Considerations 15-19
15.5.9 Tolerance Requirements 15-20

16: MASS CONCRETE FORMWORK

16.1 Types of Cantilever Forms in Common Use 16-2

xvi
 16.2 Design Considerations 16-3
16.2.1 Loads on the Formwork 16-4
16.2.2 Anchorage Accessories 16-5
16.2.3 Other Design Features 16-6

16.3 Handling, Erecting, Stripping 16-7

16.4 Non-Cantilevered Formwork 16-7
16.5 Facings for Roller-Compacted Mass Concrete and Dam Repair 16-8
16.6 Foundations or Starting Lifts 16-9
16.7 Curing, Joint Cleanup, Insulation 16-10
16.8 Planning and Supervision 16-11
16.9 Tolerances 16-11

17: TUNNEL AND SHAFT FORMWORK

17.1 Tunnel Forming Components 17-1
17.1.1 Curb Forms 17-2
17.1.2 Invert Forms 17-2
17.1.3 Arch Forms 17-3
17.1.4 Form Traveler Operations 17-5

17.2 Concrete Placement Methods 17-5

17.2.1 Continuous Advancing Slope 17-6
17.2.2 Bulkhead Method 17-6
17.2.3 Cut-and-Cover Construction 17-7

17.3 General Design Considerations 17-7

17.3.1 Influence of Placing Equipment 17-7
17.3.2 Loads and Pressures 17-8
17.3.3 Vibration and Form Access 17-9

17.4 Form Construction 17-9

17.5 Stripping Time 17-10
17.6 Tolerances 17-10
17.7 Shafts 17-11

18: SPECIAL TECHNIQUES IN CONCRETE CONSTRUCTION

18.1 Vertical Slipform Construction 18-1
18.1.1 Design and Construction Considerations 18-3
18.1.2 Jacking System 18-6
18.1.3 Sliding Operations 18-6

18.2 Horizontal Slip Forms 18-8

18.2.1 Design and Construction Considerations 18-9
18.2.2 Horizontal Applications 18-9

18.3 Tilt-Up 18-12

18.3.1 Curing and Bond-Breaking Compounds 18-13
18.3.2 Curved Tilt-Up Panels 18-13

18.4 Lift Method of Construction 18-13

18.4.1 Forming and Casting 18-14
18.4.2 Slab Separation 18-14

xvii
 18.5 Shells, Domes, and Folded Plates 18-14
18.5.1 Shell Form Design Considerations 18-15
18.5.2 Building the Forms 18-16
18.5.3 Placing Concrete 18-16
18.5.4 Form Removal 18-16
18.5.5 Inflated Forming Methods 18-17

18.6 Traveling Forms 18-17

18.6.1 Applications 18-17
18.6.2 Design Considerations 18-18

18.7 Preplaced Aggregate Concrete 18-19

18.7.1 Lateral Pressure 18-19
18.7.2 Form Construction and Materials 18-20

18.8 Shotcrete 18-21

18.9 Tremie Concrete 18-21
18.10 Precast Concrete 18-23
18.10.1 Advantages of Precasting 18-23
18.10.2 Formwork Requirements 18-24
18.10.3 Stripping 18-26
18.10.4 Erection and Joints 18-26

18.11 Prestressed Precast Concrete 18-26

18.11.1 Forms for Post-Tensioning 18-27
18.11.2 Forms for Pretensioning 18-29

APPENDIX A—REFERENCED STANDARDS AND REPORTS

APPENDIX B—NOTATION

APPENDIX C—GLOSSARY

APPENDIX D—CONVERSIONS

APPENDIX E—ACI 347R-14 GUIDE

APPENDIX F—ACI 318-11 CODE AND COMMENTARY

APPENDIX G—OSHA REGULATIONS

APPENDIX H—PROBLEMS

INDEX

xviii
 (Photo courtesy Morley Builders)

1: INTRODUCTION
Formwork development has paralleled the growth of concrete construction from its
earliest uses through its many applications today. As concrete has been used for increas-
ingly complex and significant structural and architectural tasks, formwork engineers
and contractors have had to keep pace. Projects involving rapid construction schedules
create challenges for the form designer and for the control of field forming operations.
The increasing use of concrete as an architectural medium presents the form builder with
several challenges, ranging from the selection of appropriate sheathing materials to the
maintenance of rigid tolerances.
Sawn lumber, manufactured wood products, plywood, steel, aluminum, reinforced
polymers, and other materials are widely used as formwork components. In addition, new
and specialized accessories are frequently introduced by manufacturers. Form designers,
builders, and manufacturers must keep abreast of advancing technology in other material
fields to develop and implement the creative and innovative solutions required to main-
tain both quality and economy.
In the early days of the concrete industry, formwork was frequently built in place, used
once, wrecked (or stripped), and discarded. Because of high labor costs in the United
States and many other countries, the trend over the last several decades has been toward
increased prefabrication, assembly in large units, erection by mechanical means (such
as “flying” forms into place by crane), and reuse of the forms. These developments are in
harmony with the increased mechanization often found in other fields and the desired
use of sustainable systems. Consequently, the forming system selection is often a primary
factor in locating cranes and in allocating site space for storage and fabrication.
Not all of the important ideas are new, however. As early as 1908, members of the
American Concrete Institute (then called the National Association of Cement Users) were
debating the relative merits of wood and steel formwork at their annual convention.
The discussion followed a presentation proclaiming the advantages of a modular metal
panel forming system.1.1 It could be adapted for most any project, had its own connecting
hardware, and was good for extensive reuse. By 1910, steel forms for paving were being

1-1
 produced commercially and used in the field. Continuing refinement of basic ideas such as these
represents another area of ongoing progress within the formwork industry. Today, formwork and
forming systems have become an integral part of the entire equipment array on site and of the
overall construction planning process. The comparison of metal versus wood and job-built versus
manufactured systems (Fig. 1.1 and 1.2) continues today with many varieties in use and the deci-
sion ultimately based on factors of quality, safety, and economy for the individual project.
There are differences in forming practice details from one country to another and
even from one region of the United States to another. Some of the differences are due to
prevalent local material use, regional or country limits on supplies for manufacturers, or
preference of a contractor for a particular system due to their own inventory and profi-
ciency of their workers with the system. However, a trend of consolidation among form
and accessory manufacturers is also resulting in several form manufacturers with broad
international supply capability. Variations in formwork application are often most visible
to the public in buildings (Fig. 1.3) and bridges (Fig. 1.4). Formwork is also extensively used
for residential construction, stadiums, airports, harbors, water treatment plants, tunnels,
dams, and other facilities. Although the information presented in this manual has been
drawn from many sources worldwide, it is intended for application primarily in the United
States. Suggestions for formwork economy have been based on conditions in countries
where labor costs are high compared to material costs. In countries where labor costs are
substantially lower in relation to the price of construction materials, many of the ideas
presented regarding formwork economy likely will not have the same validity.
Many individuals, firms, and companies are usually involved in the design of the facility
to be built and in the design and construction of the formwork. The facility team typi-
cally involves structural engineers and architects who determine the requirements for the
concrete structure. For simplicity, the facility design team will usually be referred to as the
engineer/architect, although they may be referred to separately in some situations. The
formwork team may include the general contractor, formwork specialty subcontractors,
formwork engineers, form manufacturers, and form suppliers. The participating compa-
nies and firms also have formwork designers and skilled workers executing many detailed
tasks. For simplicity, the formwork team will usually be referred to as the formwork engi-
neer/contractor, although they may be referred to separately in some situations.
Form building requires both job-site innovation and engineering understanding. There is
certainly no substitute for the skill and sense of “know-how” that come with job-site experi-
ence. In a similar manner, many engineering principles can be used to improve the safety,
quality, and economy of formwork.

Fig. 1.1: Manufactured metal formwork

system for concrete floor slab construction
(Photo courtesy MEVA Formwork Systems) Fig. 1.2: Job-built wall formwork constructed of wood materials

1-2 CHAPTER 1