ISO/FDIS 5091-3

Structural intervention of existing concrete structures using cementitious materials — Part 3: Bottom-surface (soffit) underlaying

Intervention structurelle sur les structures en béton existantes utilisant des matériaux cimentaires — Partie 3: Recouvrement de la surface inférieure (soffite)

General Information

• Status: Not Published
• ICS: 91.080.40 - Concrete structures
• Technical Committee: ISO/TC 71/SC 7 - Maintenance and repair of concrete structures
• Drafting Committee: ISO/TC 71/SC 7 - Maintenance and repair of concrete structures
• Current Stage: 5020 - FDIS ballot initiated: 2 months. Proof sent to secretariat
• Start Date: 26-Apr-2023
• Completion Date: 26-Apr-2023

Standards Content (Sample)

DRAFT INTERNATIONAL STANDARD
ISO/DIS 5091-3
ISO/TC 71/SC 7 Secretariat: KATS
Voting begins on: Voting terminates on:
2022-07-19 2022-10-11
Structural intervention of existing concrete structures
using cementitious materials —
Part 3:
Bottom-surface (soffit) underlaying
ICS: 91.080.40
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
This document is circulated as received from the committee secretariat.
NOT BE REFERRED TO AS AN INTERNATIONAL
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NATIONAL REGULATIONS.
ISO/DIS 5091-3:2022(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
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PROVIDE SUPPORTING DOCUMENTATION. © ISO 2022
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ISO/DIS 5091-3:2022(E)
DRAFT INTERNATIONAL STANDARD
ISO/DIS 5091-3
ISO/TC 71/SC 7 Secretariat: KATS
Voting begins on: Voting terminates on:
Structural intervention of existing concrete structures
using cementitious materials —
Part 3:
Bottom-surface (soffit) underlaying
ICS: 91.080.40
COPYRIGHT PROTECTED DOCUMENT
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENT AND APPROVAL. IT IS
© ISO 2022
THEREFORE SUBJECT TO CHANGE AND MAY
This document is circulated as received from the committee secretariat.

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

NOT BE REFERRED TO AS AN INTERNATIONAL

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CH-1214 Vernier, Geneva
POTENTIAL TO BECOME STANDARDS TO
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NATIONAL REGULATIONS.
Website: www.iso.org ISO/DIS 5091-3:2022(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
Published in Switzerland
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
© ISO 2022 – All rights reserved
PROVIDE SUPPORTING DOCUMENTATION. © ISO 2022
---------------------- Page: 2 ----------------------
ISO/DIS 5091-3:2022(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction .............................................................................................................................................................................................................................. vi

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 2

3 Terms and definitions .................................................................................................................................................................................... 2

3.1 General ........................................................................................................................................................................................................... 2

4 Investigation of existing structure...................................................................................................................................................2

4.1 General ........................................................................................................................................................................................................... 2

4.2 Investigation ............................................................................................................................................................................................. 2

4.2.1 Investigation using documents, records, etc. ........................................................................................... 2

4.2.2 On-site investigation ....................................................................................................................................................... 3

5 Intervention design........................................................................................................................................................................................... 3

5.1 General ........................................................................................................................................................................................................... 3

5.2 Structural plan ....................................................................................................................................................................................... 4

5.3 Structural details ................................................................................................................................................................................. 4

6 Materials ....................................................................................................................................................................................................................... 4

6.1 General ........................................................................................................................................................................................................... 4

6.2 Materials in existing structure ................................................................................................................................................ 5

6.3 Materials used in repairing or strengthening parts ............................................................................................. 5

6.3.1 General ........................................................................................................................................................................................ 5

6.3.2 Cementitious materials ................................................................................................................................................ 5

6.3.3 Reinforcing materials .................................................................................................................................................... 5

6.3.4 Bonding products .............................................................................................................................................................. 5

6.4 Characteristic values and design values of materials for repaired or strengthened

parts ................................................................................................................................................................................................................. 6

6.4.1 General ........................................................................................................................................................................................ 6

6.4.2 Cementitious materials ................................................................................................................................................ 6

6.4.3 Reinforcing materials .................................................................................................................................................... 6

6.4.4 Bonding products .............................................................................................................................................................. 6

7 Actions ............................................................................................................................................................................................................................ 6

7.1 General ........................................................................................................................................................................................................... 6

7.2 Actions for intervention design ............................................................................................................................................... 6

8 Performance verification for repaired or strengthened structure ..............................................................6

8.1 General ........................................................................................................................................................................................................... 6

8.2 Calculation of response values ................................................................................................................................................. 7

8.2.1 General ........................................................................................................................................................................................ 7

8.2.2 Modeling of structure .................................................................................................................................................... 7

8.2.3 Structural analysis ........................................................................................................................................................... 7

8.2.4 Calculation of design response values ............................................................................................................ 7

8.3 Durability verification .................................................................................................................................................................. 11

8.4 Safety verification ............................................................................................................................................................................ 11

8.4.1 General ..................................................................................................................................................................................... 11

8.4.2 Verification related to failure .............................................................................................................................. 11

8.4.3 Verification related to fatigue failure ........................................................................................................... 18

8.5 Serviceability verification ......................................................................................................................................................... 20

8.5.1 General .....................................................................................................................................................................................20

8.5.2 Verification related to appearance .................................................................................................................. 20

8.5.3 Verification related to displacement and deformation ................................................................. 21

8.6 Restorability verification ........................................................................................................................................................... 21

8.7 Structural details .............................................................................................................................................................................. 21

8.7.1 Thickness of bottom-surface (soffit) underlaying parts.............................................................. 21

iii
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ISO/DIS 5091-3:2022(E)

8.7.2 Cover .......................................................................................................................................................................................... 21

8.7.3 Space between reinforcing materials ........................................................................................................... 22

8.7.4 Joints for reinforcing materials .......................................................................................................................... 22

8.7.5 Anchoring and securing methods of reinforcing materials ......................................................22

9 Construction ..........................................................................................................................................................................................................22

9.1 General ........................................................................................................................................................................................................22

9.2 Prior investigation and construction plan.................................................................................................................. 23

9.3 Surface treatment ............................................................................................................................................................................. 24

9.4 Assembly of reinforcing materials ..................................................................................................................................... 24

9.5 Surface preparation ........................................................................................................................................................................ 25

9.6 Storage, mixing and transportation of underlaying materials ................................................................. 25

9.7 Execution of underlaying ...........................................................................................................................................................25

9.8 Curing .......................................................................................................................................................................................................... 26

9.9 Quality control ..................................................................................................................................................................................... 26

9.10 Inspection ................................................................................................................................................................................................ 27

10 Records ...................................................................... ..................................................................................................................................................27

11 Maintenance ..........................................................................................................................................................................................................27

Annex A (informative) Examples of execution procedure .........................................................................................................28

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ISO/DIS 5091-3:2022(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to

the World Trade Organisation (WTO) principles in the Technical Barriers to Trade (TBT) see

www.iso.org/iso/foreword.html.

This document was prepared by Technical Committee ISO/TC 71, Concrete, reinforced concrete and pre-

stressed concrete, Subcommittee SC 7, Maintenance and repair of concrete structures.

A list of all parts in the ISO 5091 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www.iso.org/members.html.
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ISO/DIS 5091-3:2022(E)
Introduction

As a repairing and strengthening method, attaching of cementitious material layer to surface of

existing concrete structures has been widely accepted. Since the cementitious layer does not have

enough tensile strength, tension reinforcement is generally placed in the cementitious layer. There are

two types of attaching way. For the first way, the cementitious layer is attached either on top surface

or bottom surface of horizontal concrete members, especially slabs, while, for the second way, the

cementitious layer is attached to jacket vertical concrete members, especially columns. There has not

been ISO standard on design, execution and maintenance for this method with attaching cementitious

layer. This ISO 5091 serves as the first ISO standard for the intervention by attaching cementitious

material layer with tension reinforcement inside.

At the same time, this ISO 5091 is the first ISO standard developed for a specific intervention method,

which conforms to the umbrella code, ISO 16311 Maintenance and repair of concrete structures,

especially ISO 16311-3 – Part 3: Design of repairs and prevention and ISO 16311-4 – Part 4: Execution of

repairs and prevention.

ISO 5091 Structural intervention of existing concrete structures using cementitious materials consists

of four parts; ISO 5091-1 – Part 1: General principles, ISO 5091-2 – Part 2: Top-surface overlaying,

ISO 5091-3 – Part 3: Bottom-surface (soffit) underlaying, and ISO 5091-4 – Part 4: Jacketing. ISO 5091-1

provides the issues common to all three parts, while ISO 5091-2, 3 and 4 provide the issues specific to

each attaching way of cementitious material layers.

It is expected that this ISO 5091 could serve as a practical standard for construction industry, such as

client, design consultant and general contractor, to apply the structural intervention with externally

attached cementitious layer. Additional technical information, which is not provided explicitly in

ISO 5091, needs to be provided in each application case with consideration of the provisions of ISO 5091.

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DRAFT INTERNATIONAL STANDARD ISO/DIS 5091-3:2022(E)
Structural intervention of existing concrete structures
using cementitious materials —
Part 3:
Bottom-surface (soffit) underlaying
1 Scope

These guidelines specify the standards for design and construction using the bottom-surface (soffit)

underlaying method. Bottom-surface (soffit) underlaying is a method whereby reinforcing materials

are placed on the bottom surface of the slabs or beams whose performance is lower than required and

the improvement of durability, serviceability, safety and other performance of the members is achieved

by the integrity between the reinforcing materials and existing members.

Generally, polymer hydraulic cement mortar (hereinafter PCM) is used as the underlaying material.

This is because PCM bonds well with the existing members and has large tensile strain at cracking, and

making the penetration of degradation factors less likely. As reinforcing materials, reinforcing steel,

welded wire mesh, FRP grid are used.

Bottom-surface (soffit) underlaying has evolved as a strengthening method for fatigue of RC decks,

drawing attention because of examples of applications like the one shown in Figure 1. The members

that are currently repaired or strengthened using this method include RC decks, tunnel linings, box

culverts, waterways and beams. In these guidelines, the latest information about the design and

construction of the bottom-surface (soffit) underlaying method using underlaying materials has been

collected and the best possible standards are presented. Matters not mentioned herein shall be as set

forth in ISO /NP 5091-1.

Figure 1 — Example of application of bottom-surface (soffit) underlaying for deck

strengthening
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ISO/DIS 5091-3:2022(E)
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 16311-1:2014, Maintenance and repair of concrete structures — Part 1: General principles

ISO 16311-2:2014, Maintenance and repair of concrete structures — Part 2: Assessment of existing concrete

structures

ISO 16311-3:2014, Maintenance and repair of concrete structures — Part 3: Design of repairs and

prevention

ISO 16311-4:2014, Maintenance and repair of concrete structures — Part 4: Execution of repairs and

prevention
ISO 22966:2009, Execution of concrete structures
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1 General

The definitions of the terms used in the Bottom-surface (soffit) underlaying section shall be as defined

in Clause 3 of ISO / NP 5091-1.
4 Investigation of existing structure
4.1 General

The study of the existing structure for which to consider intervention using the bottom-surface (soffit)

underlaying method shall be as set forth in Clause 4 of ISO /NP 5091-1.
4.2 Investigation
4.2.1 Investigation using documents, records, etc.

When the climatic conditions, environmental conditions and geographical conditions of the local site

are studied using documents, records, etc., the study shall be conducted in accordance with 4.2.1 of ISO

/NP 5091-1.
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ISO/DIS 5091-3:2022(E)
4.2.2 On-site investigation

The on-site study on degradation, damage and initial defects of the existing concrete structure shall be

conducted in accordance with 4.2.2 of ISO /NP 5091-1.

NOTE It is necessary to check that the shape, size and other characteristics of the existing members subject

to bottom-surface (soffit) underlaying are consistent with the documents and records. In the investigation,

the steel materials of the existing members need to be checked in terms of size, arrangement, etc. through a

non-destructive inspection, chipping inspection or the like as necessary. Also, the degree of degradation and

the progress of damage of the existing members subject to bottom-surface (soffit) underlaying shall be grasped

through checking for changes in appearance (cracks, water leaks, efflorescence, rust staining flaking and peeling

of cover concrete, and exposed reinforcing bar, etc.), measurement of chloride-ion concentration, checking of the

carbonation depth, covering depth and degree of steel corrosion, etc. At the same time, the causes of degradation

and damage shall be presumed based on the surrounding environment (coastal lines, traffic conditions, climatic

conditions, etc.), the characteristics of damage, the flow of rainwater, water leaks, vibration generated when

heavy vehicles pass and so forth.

The work environment and other relevant conditions of the site shall be checked in advance.

NOTE It is necessary to check the status of the approach route for work vehicles, work machines, etc. as well

as whether the storage space and temporary structures such as scaffoldings can be set up.

5 Intervention design
5.1 General

When repairing or strengthening a concrete structure using bottom-surface (soffit) underlaying, it shall

be verified by means of an appropriate method that the structure fulfills the required performance

for the required period. Also, the environment for the intervention construction, constructability, post-

intervention maintainability and economy shall be taken into consideration.

NOTE Bottom-surface (soffit) underlaying is applied for purposes such as flexural strengthening and shear

strengthening of structural members by providing thin reinforcing underlaying layers. One feature of this method

is that the increase in weight due to intervention is small. When it is used for box culverts, tunnels, waterways,

etc., there is only a small reduction in the inner section. When structural members such as bridge decks are

repaired or strengthened using bottom-surface (soffit) underlaying, a verification related to the punching

shear failure of the decks needs to be performed. In the case of waterways or box culverts, it is necessary to

verify ordinary design loads such as earth pressure and water pressure. Even for tunnels and water channels,

a verification related to level 2 ground motions may be required. While the verification methods described in

these guidelines do not cover all kinds of verification, the currently available latest technologies are presented

herein.

NOTE An example of the construction section observed when bottom-surface (soffit) underlaying is applied

to bridge decks is shown in Annex.

NOTE Bottom-surface (soffit) underlaying requires that underlaying materials protect reinforcing materials

from corrosion as well. With the bottom-surface (soffit) underlaying method using PCM, the thickness of

underlaying parts is 30 mm or so in many cases. Therefore, underlaying materials can be applied to underlaying

parts by either spraying or trowelling. A rational method should be selected taking into consideration the

application environment and quantity.
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ISO/DIS 5091-3:2022(E)
5.2 Structural plan

The structural plan for a structure repaired or strengthened with bottom-surface (soffit) underlaying

shall be as set forth in 5.2 of ISO /NP 5091-1.

NOTE The repaired or strengthened structure shall fulfill the required levels of durability, safety,

serviceability and restorability throughout the design service life. The performance requirements differ

depending on the structure repaired or strengthened with bottom-surface (soffit) underlaying. In flexural

strengthening of existing members, the verification is mainly intended for serviceability, safety, etc. In fatigue

strengthening of bridge decks, the punching shear capacity of the decks is required to be improved. In seismic

strengthening of box culverts and tunnels, the verification is intended for restorability. Also, the intervention

shall be planned taking into consideration the causes of degradation and damage of the existing members subject

to bottom-surface (soffit) underlaying.

NOTE Since thin members are used as underlaying materials in bottom-surface (soffit) underlaying, the

covering of reinforcing materials becomes relatively thin. This makes it possible for degradation factors to

intrude more quickly in a severe corrosion environment. Therefore, durability verification is a key point in

maintenance and necessary measures shall be considered.
5.3 Structural details

The structure of bottom-surface (soffit) underlaying shall ensure the integrity between the existing

and underlaying parts in
...