Description
Introduction to the ACI 562-19 Code
Advancements in the practice of assessment, repair, rehabilitation, and strengthening of concrete structures have developed through a collaboration of design professionals, contractors, suppliers, manufacturers, researchers, educators, and lawyers. The annual cost to owners for repair, protection, and strengthening of existing concrete structures is estimated between $18 and $21 billion (Vision 2020). Simply put, even sound concrete may require repair, rehabilitation, maintenance, or strengthening throughout the service life of a structure. Accordingly, from 2004 to 2006, the Strategic Development Council (SDC), an interindustry development group dedicated to supporting the concrete industry’s strategic needs, facilitated the development of “Vision 2020: A Vision for the Concrete Repair, Protection, and Strengthening Industry” to establish a set of goals that would improve the efficiency, safety, and quality of concrete repair and protection activities. One of the goals established by Vision 2020 was to create a concrete repair and rehabilitation code by 2015. The ACI 562-13 standard, “Code Requirements for Evaluation, Repair, and Rehabilitation of Concrete Buildings and Commentary,” is the end result of that initiative. ACI 562-19 is the third edition of the Code with revisions, additions, and reorganized information to enhance the Code, providing more clarity and additional, updated information to assist the design professional.
The purpose of the ACI 562 Code is to provide minimum material and design requirements for the assessment, repair, and rehabilitation of structural concrete members. Like other ACI codes, ACI 562 is organized in a dual-column format, with mandatory code provisions to the left of each page, and nonmandatory commentary to the right to provide additional guidance and information on the content presented in the Code provisions. Unlike other ACI standards, ACI 562 includes both prescriptive and performance requirements. The performance requirements provide great latitude and flexibility to the licensed design professional in satisfying the requirements of ACI 562. Accordingly, ACI 562 serves to unify and strengthen concrete assessment, repair, and rehabilitation projects while accommodating the diverse and unique strategies and materials used in the industry.
In general, the overall use and function of ACI 562, with respect to existing concrete structures, can be compared to that of ACI 318-19, “Building Code Requirements for Structural Concrete and Commentary,” with new concrete construction. As with ACI 318 and the 2018 International Building Code (2018 IBC), plans are underway for ACI 562 an ANSI standard, to be adopted into the International Existing Building Code (IEBC) to address matters pertaining to assessment, repair, rehabilitation, and strengthening of concrete members within existing buildings. Local jurisdictions and building authorities can also adopt ACI 562 directly. Cities and states have both adopted ACI 562 and adopted use of ACI 562 on specific projects. Other jurisdictions are in the process of reviewing the Code for consideration and adoption. Accordingly, while ACI 562 currently defines the standard for the concrete assessment, repair, and rehabilitation industry, the code provisions of ACI 562 will likely then become mandatory requirements as part of the governing building codes that regulate work in existing buildings.
Overview of the guide to ACI 562 Code content
The primary purpose of this guide is to help licensed design professionals (LDPs) gain more knowledge, skill, and judgment to interpret and properly use the ACI 562 Code. Although specifically developed for LDPs, this guide also provides insight into the use and benefits of ACI 562 for contractors, material manufacturers, and building owners and building officials. To achieve this goal, the guide is separated into three main components: Chapter Guides including Appendix A, Project Examples, and Appendix B, providing an overall view of the new standard, ACI 563, “Specifications for Repair of Concrete in Buildings.”
The Chapter Guides and Project Examples are provided in tandem for clarity and understanding of the relative portions of ACI 562 Code. The Project Examples illustrate the process of carrying out a concrete building assessment, repair, rehabilitation, or strengthening project from inception through completion. This guide, including the Project Examples, is intended as a supplement to the ACI 562 Code and not as a “how-to” manual for performing concrete assessment, repair, rehabilitation, or strengthening. Several additional documents are referenced in ACI 562 Commentary and this guide to assist in evaluating the various options and approaches to performing successful concrete assessment, repair, rehabilitation, or strengthening projects. The intent of each Project Example is not to be a prescriptive formula for each of the project scenarios presented, but to illustrate how various sections of ACI 562 are applied together to execute the project. For convenience, related provision numbers from ACI 562 are given at the top of each corresponding paragraph of the project example text. Eight Project Examples are included within the guide:
1. Typical parking structure repairs
2. Typical façade repairs
3. Repair of historic structure for adaptive reuse
4. Strengthening of two-way flat slab
5. Strengthening of double-tee stems for shear
6. Concrete beam repair by section enlargement
7. Concrete repair by steel jacket
8. Beam repair with fire protection analysis:
a. Beam strengthening due to live load increase
b. Beam with inadequate existing concrete cover
In the third edition of this repair guide, a new chapter, Appendix B, was added to address specifications. This is another goal by Vision 2020 to create a concrete repair specification standard. The ACI 563-18 standard, “Specification for Repair of Concrete in Buildings,” is a reference standard that the LDP can apply to any construction repair and rehabilitation project involving structural concrete by citing it in the Project Specifications. It provides direction to the contractor and clearly defines the responsibilities and scope of the repair, rehabilitation, or strengthening. The specifications detail the work, material, and installation required to complete a project the way the client wants.
The Chapter Guides follow the general organization of ACI 562, broken down by the corresponding sections of ACI 562. Section numbers in Chapters 1 to 10 and Appendix A of this guide correspond to the provision numbers in ACI 562. The Chapter Guides include background information and an explanation of the various ACI 562 provisions, with particular insight into how the particular chapter and section of the Code fit within the project. Where applicable, flowcharts are provided to illustrate how to navigate the various provisions of ACI 562. References to Project Examples are provided where applicable to illustrate how specific provisions within each chapter of ACI 562 are incorporated into the design process. In some instances, additional limited-scope examples are included to better illustrate a point that is not covered by the Project Examples.
The first edition of ACI 562 was published in 2013, and was not available when the work for the projects discussed in the Project Examples was actually performed. All Project Examples assume that ACI 562 was available and accepted by local jurisdiction when the example projects were performed.
The second edition of ACI 562, published in 2016, includes additional definitions used in the Code for consistency with 2018 IEBC and other similar standards for existing structures. The title of ACI 562-16 was changed by replacing the word “Evaluation” with “Assessment.” The two terms, which are used interchangeably by other standards and the first version of this Code, have received distinct definitions in the second edition of ACI 562 (Stevens et al. 2016). Specific criteria requirements for assessment and design of repair and rehabilitation for varying levels of damage, deterioration, or faulty construction was added in Chapter 4 when using the Code with IEBC, and in Appendix A when using the Code as a stand-alone code. Chapters 1 and 4 were revised to include specific criteria requirements for assessment and design of repair and rehabilitation for varying levels of damage, deterioration, or faulty construction. Load combinations in Chapter 5, which define the minimum strength of a structure with unprotected external reinforcement, were revised. Chapter 6 directs the LDP to provide an assessment before rehabilitation of an existing structure. This chapter includes historical material property data to help the design professional in the assessment if existing documents related to the existing structure are not available or physical samples cannot be extracted, because of the historical value of the structure. The interface bond provisions in Chapter 7 were revised to provide specific requirements based on shear test, as well as when to provide interface reinforcement, and commentary in Chapter 8 was clarified.
The third edition of ACI 562, published in 2019, has:
(a) Added text to simplify use of new materials that have the equivalent of an ICC-ES evaluation report in Chapter 1;
(b) Simplified the requirements for the basis of design reported in Chapter 1;
(c) Clarified requirements related to detailing of existing reinforcing steel in Chapter 7; and
(d) Updated commentary in Chapter 8 to include a listing of exposure categories that may affect durability.
In addition, three new repair examples are added to demonstrate the flexibility of the Code and its applicability to different repair and strengthening methods. Example 6 is related to concrete beam repair by section enlargement, Example 7 addresses concrete frame strengthening by steel jacketing, and Example 8 focuses on the effect of fire on concrete members and possible protection based on two scenarios: scenario one—concrete structure subjected to increase in live load; and scenario two—reinforcement with low concrete cover.
Lastly, a summary of the various provisions of ACI 562, as well as the corresponding location where each provision is covered within the guide, is provided in the Provision Coverage Matrix at the end of this guide. This serves as a useful tool when searching for additional information to a specific provision of ACI 562.
Table of Contents
Acknowledgments 6
Preface 7
About This Book 12
Chapter 1—General Requirements 13
1.1—General 13
1.2—Criteria for the assessment and design of repair and rehabilitation of existing concrete structures 14
1.3—Applicability of the Code 15
1.4—Administration 16
1.5—Responsibilities of licensed design professional 16
1.6—Construction documents 16
1.7—Preliminary assessment 16
Chapter 2—Notation and Definitions 19
2.1—Notation 19
2.2—Definitions 19
Chapter 3—Referenced Standards 21
Chapter 4—Basis for Compliance 23
4.1—General 23
4.2—Compliance method 24
4.3—Potentially dangerous structural conditions 25
4.4—Substantial structural damage 26
4.5—Conditions of deterioration, faulty construction, or damage less than substantial structural damage 26
4.6—Conditions of deterioration, faulty construction, or damage less than substantial structural damage without strengthening 30
4.7—Additions, 4.8—Alterations, 4.9—Changes in occupancy 30
Chapter 5—Loads, Factored Load Combinations, and Strength Reduction Factors 31
5.1—General 32
5.2—Load factors and load combinations 33
5.3—Strength reduction factors for repair design 33
5.4—Strength reduction factors for assessment 33
5.5—Additional load combinations for structures rehabilitated with external reinforcing systems 34
Chapter 6—Assessment, Evaluation, and Analysis 37
6.1—Structural assessment 37
6.2—Investigation and structural evaluation 38
6.3—Material properties 40
6.4—Test methods to determine or confirm material properties 44
6.5—Structural analysis of existing structures 45
6.6—Structural serviceability 45
6.7—Structural analysis for repair design 45
6.8—Strength evaluation by load testing 46
6.9—Recommendations 46
Chapter 7—Design of Structural Repairs 47
7.1—General 47
7.2—Strength and serviceability 47
7.3—Behavior of repaired systems 48
7.4—Interface bond 49
7.5—Materials 57
7.6—Design and detailing considerations 57
7.7—Repair using supplemental post-tensioning 58
7.8—Repair using fiber-reinforced polymer (FRP) composites 59
7.9—Performance under fire and elevated temperatures 60
Chapter 8—Durability 61
8.1—General 61
8.2—Cover 62
8.3—Cracks and deterioration of reinforcement and metallic embedments 62
8.4—Corrosion 63
8.5—Surface treatments and coatings 64
Chapter 9—Construction 65
9.1—General 65
9.2—Stability and temporary shoring requirements 65
9.3—Temporary conditions 66
9.4—Environmental issues 68
Chapter 10—Quality Assurance 69
10.1—General 69
10.2—Inspection 70
10.3—Testing of repair materials 70
10.4—Construction observations 70
Chapter 11: Commentary References 71
Appendix A—Criteria When Using ACI 562 as a Stand-Alone Code 73
A.1—General 73
A.2—Design-basis code criteria 73
A.3—Potentially dangerous structural conditions 75
A.4—Substantial structural damage 76
A.5—Conditions of deterioration, faulty construction, or damage less than substantial structural damage 76
A.6—Conditions of deterioration, faulty construction, or damage less than substantial structural damage without strengthening 78
A.7—Additions 79
A.8—Alterations 80
A.9—Changes in occupancy 82
Appendix B—Repair Guide 83
General 83
Section 1—General requirements 83
General procedures 84
Preinstallation conference 84
Quality assurance, quality control, testing, and inspection 85
Quality assurance (QA) 85
Advantages of quality assurance 87
Disadvantages of quality assurance 87
Quality control (QC) 87
Advantages of quality control 87
Disadvantages of quality control 87
Testing and inspection 88
Section 2—Shoring and bracing 90
Section 3—Concrete removal and preparation for repair 91
Section 4—Formwork 94
Section 5—Reinforcement and reinforcement supports 97
Section 6—Conventional concrete mixtures 99
Section 7—Handling and placing of conventional concrete 101
Section 8—Proprietary cementitious and polymer repair materials 102
Sections 9 and 10 102
Notes to Specifier (nonmandatory) 102
Checklists 102
Project Examples 104
Chapter 12: Project Example 1—Typical Parking Structure Repair 105
Description of structure 105
Project initiation and objectives 105
Governing building codes 106
Preliminary assessment 107
Investigation of existing site conditions 107
Capacity and demand of existing structure 108
Findings of preliminary assessment 108
Area 1 109
Area 2 111
Report to owner 113
Structural Assessment 113
Existing conditions 113
Structural analysis for repair design 114
Area 1 115
Area 2 115
Design of structural repairs and durability 116
Slab Area 1 116
Slab Area 2 and columns 117
Slab soffit repairs 118
Construction specifications 118
Construction 119
Quality assurance 119
Project close-out 120
Periodic maintenance 120
Record documents 120
Chapter 13: Project Example 2—Typical Façade Repair 121
Description of structure 121
Project initiation and objectives 122
Governing building codes 122
Preliminary observations and assessment 123
Observed concrete conditions 124
Laboratory findings 125
Findings 125
Structural assessment and repair design 126
Shear wall reveal strip repairs 126
North and south walls away from reveal strips and east and west slab and column edges 128
Balcony repairs 128
Performance under fire and elevated temperatures 130
Contract specifications 130
Construction 131
Quality assurance 131
Project close-out 132
Periodic maintenance 132
Record documents 132
Chapter 14: Project Example 3—Adaptive Reuse of Historic Depot 133
Description of structure 133
Project initiation and objectives 134
Governing building codes 134
Preliminary observations and evaluation 135
Concrete conditions 135
Material evaluation findings 137
Summary 137
Structural assessment 138
Requirement for structural assessment 138
Existing properties 138
Structural analysis 138
Structural analysis findings 139
Recommended repair program 140
Train deck rehabilitation 140
Column rehabilitation 142
Concrete repair details 144
Contract specifications 146
Construction 148
Quality assurance 148
Project close-out 148
Periodic maintenance 148
Record documents 148
Chapter 15: Project Example 4—Parking/Plaza Slab Strengthening 149
Description of structure 149
Project initiation and objectives 149
Governing building codes 149
Preliminary evaluation 150
Document review 150
Existing site conditions 150
Strength of as-built structure 150
Compliance method and design-basis code 153
Structural assessment 154
Requirement for structural assessment 154
Structural assessment 154
Structural analysis 155
Strengthening concepts 155
Strengthening Concept 1 155
Strengthening Concept 2 155
Assessment of strengthening concepts 156
Structural analysis for repair design 157
Design of structural repairs and durability 159
Contract specifications 160
Construction 163
Quality assurance 163
Load test 163
Test procedure 163
Test results 167
Project close-out 168
Periodic maintenance 168
Record documents 168
Chapter 16: Project Example 5—Precast/Prestressed Double-Tee Repair 169
Description of structure 169
Project initiation and objectives 169
Governing building codes 170
Preliminary assessment 171
Existing site conditions 171
Design strength of existing structure 171
Findings of preliminary assessment 171
Design-basis code 173
Structural evaluation 173
Existing site conditions 173
Structural analysis for evaluation 174
Structural safety 176
Repair/replacement options 176
Repair/replacement Option 1 176
Repair/replacement Option 2 177
Repair/replacement Option 3 177
Repair/replacement Option 4 178
Evaluation of repair/replacement options 179
Design of strengthening repairs 179
Structural analysis for repair design 179
Design of strengthening repairs 180
Design of structural repairs and durability 181
Development and bond of CFRP strips 181
Acceptance of CFRP repairs by the authorities having jurisdiction 182
Durability of repairs 182
Aesthetics of repairs 182
Contract specifications 182
Construction 183
Quality assurance 183
Project close-out 186
Periodic maintenance 186
Record documents 186
Chapter 17: Project Example 6—Concrete Beam Repair by Section Enlargement 187
Description of structure 187
Project initiation and objectives 187
Governing building code 188
Structural assessment 189
Structural analysis 189
Repair options 190
Design of repairs 191
Durability of repairs 192
Contract documents 193
Construction specifications 193
Construction 193
Quality assurance/construction observations 193
Project Close-out 194
Periodic maintenance 194
Record documents 194
Chapter 18: Project Example 7—Concrete Frame Strengthening by Steel Jacket 195
Description of structure 195
Project initiation and objectives 195
Governing building codes 196
Preliminary evaluation 196
Strengthening concepts 199
Structural analysis and repair design 199
Durability 200
Contract documents 200
Construction specifications 200
Construction 203
Quality assurance 203
Project close-out 204
Periodic maintenance 204
Record documents 204
Chapter 19: Project Example 8—Building Subjected to Fire 205
Description of structure 205
Project initiation, objectives, and remediation summary 206
Governing codes 208
Fire resistance rating calculations 208
Contract specifications 217
Construction 218
Quality assurance 218
Load test 218
Test procedure 218
Project close-out 219
Periodic maintenance 219
Record documents 219
References 219
Referenced Standards and Reports 221
Authored documents 224