[BS ISO 16311-1] -- Maintenance and repair of concrete structures. Part 1. General principles.pdf

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Title: Draft BS ISO 16311-1 Maintenance and repair of concrete structures

Part 1: General principles

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© International Organization for Standardization, 2011

DRAFT INTERNATIONAL STANDARD ISO/DIS 16311-1

ISO/TC 71/SC 7 Secretariat: KATS

Voting begins on Voting terminates on 2011-06-24 2011-11-24

INTERNATIONAL ORGANIZATION FOR STANDARDIZATION • МЕЖДУНАРОДНАЯ ОРГАНИЗАЦИЯ ПО СТАНДАРТИЗАЦИИ • ORGANISATION INTERNATIONALE DE NORMALISATION

Maintenance and repair of concrete structures — Part 1: General principles

Entretien et réparation des structures en béton —

Partie 1: Principes généraux

ICS 91.100.30

In accordance with the provisions of Council Resolution 15/1993 this document is circulated in the English language only.

Conformément aux dispositions de la Résolution du Conseil 15/1993, ce document est distribué en version anglaise seulement.

To expedite distribution, this document is circulated as received from the committee secretariat. ISO Central Secretariat work of editing and text composition will be undertaken at publication stage.

Pour accélérer la distribution, le présent document est distribué tel qu'il est parvenu du secrétariat du comité. Le travail de rédaction et de composition de texte sera effectué au Secrétariat central de l'ISO au stade de publication.

ISO/DIS 16311-1

Copyright notice This ISO document is a Draft International Standard and is copyright-protected by ISO. Except as permitted under the applicable laws of the user’s country, neither this ISO draft nor any extract from it may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, photocopying, recording or otherwise, without prior written permission being secured. Requests for permission to reproduce should be addressed to either ISO at the address below or ISO’s member body in the country of the requester.

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ii © ISO 2011 – All rights reserved

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Contents Page

Foreword ---------------------------------------------------------------------------------------------------------4 Introduction -----------------------------------------------------------------------------------------------------5 1. Scope -------------------------------------------------------------------------------------------------------------6

2. Normative references -----------------------------------------------------------------------------------------6 3. Terms and definitions ---------------------------------------------------------------------------------------6 4. Basis of maintenance----------------------------------------------------------------------------------9 4.1 General ------------------------------------------------------------------------------------------------------------------9 4.2 Procedure of maintenance ---------------------------------------------------------------------------------------9 4.3 Competence of personnel --------------------------------------------------------------------------------------10 5. Maintenance plan --------------------------------------------------------------------------------------------10 5.1 General ----------------------------------------------------------------------------------------------------------------10 5.2 Timing of maintenance planning for structures ---------------------------------------------------------10 5.3 Selection of maintenance category --------------------------------------------------------------------------11 5.4 Final determination of maintenance plan ------------------------------------------------------------------11 6. Assessment-----------------------------------------------------------------------------------------------------------11 6.1 General------------------------------------------------------------------------------------------------------------------11 6.2 Assessment plan----------------------------------------------------------------------------------------------------11 6.2.1 Preparation of assessment plan-------------------------------------------------------------------------------11 6.2.2 Category of assessment-----------------------------------------------------------------------------------------11 6.2.3 Level of assessment-----------------------------------------------------------------------------------------------12 6.3 Investigation ---------------------------------------------------------------------------------------------------------12 6.3.1 Implementation plan ----------------------------------------------------------------------------------------------12 6.3.2 Selection of items -------------------------------------------------------------------------------------------------12 6.3.3 Identification of locations ---------------------------------------------------------------------------------------13 6.3.4 Selection of method ----------------------------------------------------------------------------------------------13 6.3.5 Selection of tools and techniques ---------------------------------------------------------------------------13 6.3.6 Frequency of investigation -------------------------------------------------------------------------------------13 6.3.7 Emergency measures after investigation -----------------------------------------------------------------13 6.3.8 Monitoring ------------------------------------------------------------------------------------------------------------14 6.4 Prediction of deterioration and performance degradation of structure------------------14 6.4.1 Identification of deterioration mechanisms ---------------------------------------------------------------14 6.4.2 Determination of deterioration level and rate ------------------------------------------------------------14 6.4.3 Prediction of performance degradation of structure --------------------------------------------------14 6.5 Evaluation and decision-----------------------------------------------------------------------------------------15 6.5.1 Evaluation of performance of structure--------------------------------------------------------------------15 6.5.1.1 Performance verification method ----------------------------------------------------------------------------15 6.5.1.2 Threshold levels for performance degradation of structure ----------------------------------------15 6.5.1.3 Overall evaluation of performance level possessed---------------------------------------------------15 6.5.2 Decision ---------------------------------------------------------------------------------------------------------------15 7. Remedial actions ---------------------------------------------------------------------------------------------------15 7.1 Selection of remedial action ------------------------------------------------------------------------------------15 7.2 Repair ------------------------------------------------------------------------------------------------------------------16 7.2.1 General ----------------------------------------------------------------------------------------------------------------16 7.2.2 Planning and design ----------------------------------------------------------------------------------------------16 7.2.2.1 Formulation of repair plan --------------------------------------------------------------------------------------16 7.2.2.2 Repair level ----------------------------------------------------------------------------------------------------------16

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7.2.2.3 Selection of methods and material -------------------------------------------------------------------------17 7.2.2.4 Design for repair -------------------------------------------------------------------------------------------------17 7.2.3 Execution -----------------------------------------------------------------------------------------------------------17 7.2.3.1 Execution plan ----------------------------------------------------------------------------------------------------17 7.2.3.2 Quality control in execution ----------------------------------------------------------------------------------17 7.2.3.3 Completion inspection -----------------------------------------------------------------------------------------17 7.3 Other remedial actions -----------------------------------------------------------------------------------------17 7.3.1 General --------------------------------------------------------------------------------------------------------------17 7.3.2 Strengthening -----------------------------------------------------------------------------------------------------17 7.3.3 Intensified inspection -------------------------------------------------------------------------------------------18 7.3.4 Restriction in service -------------------------------------------------------------------------------------------18 7.3.5 Dismantling and removal --------------------------------------------------------------------------------------18 7.4 Special care for emergency -----------------------------------------------------------------------------------18 8. Recording------------------------------------------------------------------------------------------------------------18 8.1 General ---------------------------------------------------------------------------------------------------------------18 8.2 Period of preservation ------------------------------------------------------------------------------------------18 8.3 Method of recording --------------------------------------------------------------------------------------------19 8.3.1 Format of records and its accessibility -------------------------------------------------------------------19 8.3.2 Items included in records -------------------------------------------------------------------------------------19 8.3.3 Records concerning remedial action ----------------------------------------------------------------------19

Annex A ---------------------------------------------------------------------------------------------------------------------------20 Annex B ---------------------------------------------------------------------------------------------------------------------------21 Annex C ---------------------------------------------------------------------------------------------------------------------------22 Annex D ---------------------------------------------------------------------------------------------------------------------------24

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Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of prepa ring International Standards is normally carried out thro ugh ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be repr esented 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.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of techni cal committees is to prep are International Standards. Draft International Standa rds adopted by t he technical committees are circulated to the m ember bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.

Attention is drawn to the p ossibility 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.

This Draft International Standard has been prepared by Technical Committee ISO/TC 71 Subcommittee 7 “Maintenance and repair of concrete structures”, the secretariat of which is held by KITS. It consists of four parts:


Part 2: Assessment of existing structures

Part 3: Design of repair and prevention

Part 4: Execution of repair and prevention

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Introduction

In the context of this standard maintenance and repair are two closely related activities aimed at securing that a concrete structure (here-in-after referred to as “structure”) is retained in a state in which it can perform its required functions, while in an acceptable and safe condition. Maintenance will be used as a general term that also covers repair as a distinct activity to restore worn, damaged or deteriorated parts. For a well designed and well exe cuted concrete structure with proper maintenance, repair should not be ne cessary within the service life of the structure.

This International Standard covers the activities necessary to retain the performance of the structure above the required levels during its service life, such as:

- Maintenance planning for existing structures

- Assessment of structure including inspection/investigation and evaluation of the performance of structure

- Planning and designing repair in case it is required due to damage, deterioration or wear

- Execution of repair including preparation, execution and documentation

The main scop e of this Internationa l Standard is the maintenance and repair of existing stru ctures. Maintenance and repair procedure aims at the planning and execution of systematic routines that minimize degradation of structural performance in the intended service life and consequently can lead in a cost efficient manner.

This standard does not cover for n ewly built structures in which it is recommended that a maintenance plan should be established at the design stage. However, a so called "birth certificate" for newly built structures will be useful in later planning of maintenance and repair.

“Part 1: General principles” provides the frame work of mainten ance activities for all stru ctures or th eir components and gives general principles of each activity. As shown in Figure 1, this part is the first of four parts dealing with mainte nance and repair of con crete structures. The subsequent three parts, namely “Assessment of existing stru ctures”, “Design of repai r and prevention”, and “Execu tion of repai r and prevention” are the operational parts of this set of standards giving detailed requirements and guidelines (an extended hierarchy of the parts and other related ISO standards are shown in Annex A).

Fig. 1.1 Relationship between each part of this International Standard

MAINTENANCE AND REPAIR OF CONCRETE STRUCTURES


Maintenance plan

Assessment

Remedial action

Repair or others

Inspection/investigation

Prediction of Deterioration Progress

Evaluation/

Decision-making

Part 2: Assessment of

existing structures

Part 3: Design of repair and prevention

Part 4: Execution of repair and prevention

Performance of structure

/ structural safety

/ serviceability

/ appearance

/ mitigation of safety

risk concerning due

to falling debris of

cover concrete, etc.

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1. Scope

This International Standard covers the framework and general principles for maintenance and rep air of all kinds of existing concrete structures – un-reinforced and reinforced concrete, prestressed concrete and steel-concrete composite structures, or their structural members.

In this International Standard, deterioration is clearly distinguished from damage occurring in a short p eriod and not developing over subsequent time, such as cracking and scaling due to earthquakes or impact loading, etc. Deterioration is mainly dealt with as a target for the maintenance activities.

This International Standard also provides th e basic concept of remedial actions carried out to rest ore structural performance of existing structure by repair.

This International Standard does not cover those a spects of maintenan ce and repair that are related to serviceability and esthetics without direct impact on durability and service life, e.g. cleaning of drains, removal of vegetation, refreshment of paint etc.

This international Standard also does not cover repair of defects during execution of new structures.

2. Normative references

The following normative documents contain provisions, which through reference in this text, c onstitute provisions of this Intern ational Standard. For dated references, subsequent amendments to, or revi sions of, the publications do not a pply. However, partie s to agreements based o n this Intern ational Standard are encouraged to investigate the po ssibility of applying the most recent editions of the no rmative documents indicated below. For u ndated references, the latest edition of the norm ative document referred to appl ies. Members of ISO maintain registers of currently valid International Standards.

ISO 2394:1998. General principles on reliability for structures

ISO 15686-1:2000. Buildings and constructed assets -- Service life planning -- Part 1: General principles

ISO 13822:2010. Bases for design of structures -- Assessment of existing structures

ISO 19338:2007. Performance and assessment requirements for design standards on structural concrete

ISO 13823:2008. General principles on the design of structures for durability

ISO 16311-2. Maintenance and repair of concrete structures – Part 2: Assessment of existing structures

ISO 16311-3. Maintenance and repair of concrete structures – Part 3: Design of repair and prevention

ISO 16311-4. Maintenance and repair of concrete structures – Part 4: Execution of repair and prevention

3. Terms and definitions

For the purpose of this International Standard, the following terms and definitions shall apply with those in ISO 19338.

3.1

Maintenance and repair of concrete structures — Part 1: General principles

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assessment total set of activities performed to ve rify whether the reliability of an existi ng structure is acceptable or not for future use

3.2 design service life period of time spe cified in design of structure for which a st ructure or its members is to be used fo r its intended purpose without major repair being necessary

Note: see Fig.3.1

Fig. 3.1 Definitions of service life 3.3 deterioration process that adversely affects the performance of a structure, including reliability over time due to defects and damages caused by -- naturally occurring chemical, physical, biological, or other environmental actions -- repeated mechanical actions such as those causing fatigue -- wear due to use, abuse, and others -- improper operation and maintenance of the structure

3.4 deterioration factor factor affecting the deterioration process

3.5 durability capability of a structure or and its members to satisfy with the required performance over a specified period of time under the influence of the environmental action

Note: “durability” is often use d as qualitative term to express condition in whi ch structure maintains its required performance, such as structural safety, serviceability, and appearance, during the service life.

3.6 inspection actions collecting information on the current state of a structu re through observation and simplified non-destructive or destructive testing supplemented with materials and structural testing , as required

3.7

Performance

Initial

performance

Required

performance

Life time

Construction stage

Assessment stage

Designservice

life

Predictedservice

life

Remaining service life

Intended service

life

Remaining design service life

Performance estimated at design stage

Performance estimated at assessment

stage

Performance estimated at repair stage

Repair

Intended remaining service life

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intended remaining service life period from the time of a given inspection of a structure till the end of its intended service life

Note: see Fig.3.1

3.8 intended service life a period during which a structure is intended to be in service decided by an owner

Note: see Fig.3.1

3.9 investigation collection of information through inspection, document search, load testing and other testing

3.10 maintenance a set of activities taken to check, evaluate the performance of a stru cture, and preserve/restore it so as to satisfy performance requirements during the intended service life

3.11 maintenance category class of maintenance depending on importance, service life, environmental conditions, maintainability of the structures, etc.

3.12 maintenance plan plan realizing maintenance strategy in order to ensure that the structure retain the p erformance within the specified tolerances throughout its service life. This includes planning not only for assessment but also for repair or other remedial actions.

3.13 monitoring frequent or continuous, normally long-term, observation or measurement with recording of appropriate data for deterioration and/or performance of structure using appropriate equipment

3.14 predicted service life period of ti me estimated based on activities of assessment, such a s recorded performance, previous experience, tests, or modeling.

Note: see Fig.3.1

3.15 prevention remedial action to prevent or slow down the further deterioration of a structure or structural member and to reduce the possibility of damage to th e user or any third party, inhibiti ng the progress of deterioration, and proactively preventing deterioration

3.16 rehabilitation work required to repair and possibly upgrade an existing structure

3.17 remaining design service life period from the time of a given inspection of a structure till the end of its design service life

Note: see Fig.3.1

3.18 remaining service life period from the time of a given assessment of a structure until the end of its predicted service life

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Note: see Fig.3.1

3.19 remedial action action carried out with the obje ctive of arre sting or slowing down the dete rioration process, restoring or improving the performance of structure, or reducing the danger of damage or injury to the use r or any third party

3.20 repair remedial action adopted for resto ring structural performance and mitigate safety risks up to the initi ally required design level and to achieve the intended service life

3.21 repair plan plan for esta blishing the method an d level of repai r, determining the materials, se ctional dimensions and execution methods, specifying the control items during execution in consideration of the p olicy and level of repair

3.22 safety risks concerning due to falling debris hazards of damage and/or injury caused by concrete fragments and surface coating (finishing) materials, etc. falling from a deteriorated structure

3.23 service life actual period during which a structure meets the prescribed performance requirement

3.24 upgrading measures taken to imp rove structural performance relating to load bea ring capacity and deformation of an existing structure and/or its members

4. Basis of maintenance and repair

4.1 General

A concrete structure shall retain the required performance for the intended service life by providing necessary maintenance and repair activities, such that its performance is always above the required performance level with adequate reliability under an a ppropriate maintenance plan. A qualified person (design professional, engineer, etc.) shall d evelop a prope r maintenance plan t hat could permit a structure to retain its re quired performance

4.2 Procedure of maintenance and repair

A general flow of mai ntenance procedure is shown in Fig. 4.1. The ove rall maintenance activities shall encompass the maintenance plan, assessment (including investigation/ inspection, prediction of progress of deterioration and evaluation of structural integrity/decision-making), and shall be followed by repair or oth er remedial actions (if required). Results of these activities shall be recorded with an easily accessible format.

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Fig.4.1 General maintenance procedure

4.3 Competence of personnel

All activities of maintenan ce and repai r shall be carried out by a team of qualified persons having the adequate knowledge of design, construction, maintenance and repair of concrete structures.

5. Maintenance plan

5.1 General

For accomplishing overall maintenance activities, an adequate maintenance plan shall be formulated taking into account the maintenance category selected provisionally in accordance with Clause 5.3, intended service life, life-cycle cost and other considerations particular to the structure.

The following shall be specified in the maintenance plan:

-- required performance and its level which a structure should retain for the intended service life

-- methods and timing of assessme nt composed of in vestigation and p rediction of dete rioration of the structure or i ts structural members, performance evaluation for structure and decision of the need of remedial actions

-- basic consideration concerning repair and/or other remedial actions for the expected deteri oration/ performance degradation of structure

5.2 Timing of maintenance planning for structure

An appropriate maintenance plan shall be formulated before starting maintenance actions.

Note: In the structure’s life, there are the following three stages where a maintenance plan should be formulated :

Inspection/investigation

Prediction of deterioration

Maintenance plan

Assessment

Recording

Evaluation of performance & Decision-making

Concrete structure

Remedial action (Repair or others)

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-- At the design stage by choosing structural type and materials that satisfies maintainability -- Under service conditions when some maintenance activity is considered to be required -- After a large-scaled repair work is carried out

The last two stages are the only types of maintenance plans specified in this Standard.

5.3 Selection of maintenance category

The set of maintena nce activities are classified into different maintenance categories corresponding to the situations of a structure.

In the mainte nance plan, a suita ble maintenance category shall be provisio nally selected to carry out the maintenance work as effectively as possible in consideration of such factors as the importance of the structure, intended service life, safety concerns, environmental conditions, and ease of maintenance (see annex C).

When structural members have differe nces in thei r importance, environmental condition, safety con cerns, ease of maintenance, etc., different maintenance categories should be selected on each member even in the same structure.

5.4 Final determination of maintenance plan

When the results of initial assessment prescribed in Clause 6.2.2 suggest that the maint enance category provisionally selected is not suitable, it shall b e updated. Consequently, the maintena nce plan shall be determined in accordance with the finally selected maintenance category.

6. Assessment

6.1 General

Assessment of a structu re shall be carri ed out to ve rify its reliability after due co nsidering structural performance and durability.

An appropriate assessment plan, which incl udes planning of m ethods and procedures for investigation, prediction of deterioration progress, evaluation of actual structure condition, decision-making for necessity of remedial action, and record, shall be established after due considering the actual condition of the structure.

Note: Assessment of existing concrete structures is covered in detailer by Part 2 of this standard.

6.2 Assessment plan

6.2.1 Preparation of assessment plan

In order to identify probable critical situations for the structure, the expected condition of the structure during its intended service life should be spe cified appropriately prior to the a ssessment planning. The exp ected condition is the basis in the assessment to ensure performance of structure.

To carry out the asse ssment on a structu re rationally and economi cally, the categ ory and the level of assessment should be d ecided appropriately in t he assessment plan pri or to the co mpilation of the assessment procedure. The selected category and level of assessment depend on the assessment objectives, timing of assessments and other specific circumstances such as availability of the design and construction document, observation of damage, use of the structure.

6.2.2 Category of assessment

Assessment performed in maintenan ce activities for a structure throughout its se rvice life is catego rized suitably on the basis of the timing of assessment and the type of information desired.

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In general, the assessment is classified in the three categories (see Annex D);

-- Initial assessment: an assessment carried out for evalu ating the init ial condition of a structure before initiating into routine/regular maintenance activities.

Note: Examples of initial assessment are: -- first assessment of existing st ructures when no repair is necessary but a m aintenance plan is

recommended -- assessment of an existing structure that has undergone large-scale remedial actions -- “birth certificate” of newly constructed structures.

-- Periodic assessment: assessment carried out routinely or regularly at certain intervals prescribed in the maintenance plan

Note: When some kind of visual sign of deterioration is observed or when there is a suspicion that some kind of deterioration is going on, the assessment shall be carried out spontaneously in spite of the routine or regular interval.

-- Extraordinary assessment: assessment carried out after a structure has been subjected to an accid ental load, such as earthquake, storm, flood, fire, and impact by a vehicle or ship.

6.2.3 Level of assessment

An appropriate assessment level shall be selected depending upon the purpose and scope of the category of assessment.

In general, two level of assessment are defined as follows;

-- Preliminary level: asse ssment to co llect the basi c information on structu ral condition b y using simp le inspection/investigation methods complied with a maintenance plan, su ch as a visual i nspection and simple non-destructive test

-- Detailed l evel: assessment to obtain detaile d and sp ecific information regarding deterioration and performance degradation of the structure. Used when the assessment in the preliminary level is insufficient for identifying the deterioration and/or performance degradation or anytime when it is required

6.3 Investigation

6.3.1 Implementation plan

Investigation shall be carri ed out with the objectives of detecting deterioration and/or change in performance of the structure. Such investigation shall be carried out by inspection visually or with the hel p of appropriate methods and techniques, document search, loa d testing and other testing, etc. at appropriate intervals, depending on the import ance of the structure, the catego ry of maintenan ce, the categ ory and leve l of assessment, and the expected mechanism and the rate of deterioration.

As deterioration and/or change in performance of the st ructure are affected by environme ntal and/or loading actions, investigations shall also be conducted by an appropriate method to identify the characteristics of the environment in which the structure has been placed.

When commencing investigation, it is necessary to make an adequate imple mentation plan, which includes selection of items and method, identification of location, frequencies, etc. based on the expected deterioration prediction and past maintenance records.

6.3.2 Selection of items

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The items for investigation shall be carefully selected so that desired inform ation on the deterioration and/or structural performance can be obtained in consideration of the deteri oration mechanism expected, the category and level of assessment, and the ease of maintenance.

6.3.3 Identification of locations

Critical locations should be identified in a structure for closer attention and mo re frequent investigation. The number of the locations selected shall depend upon the category and the level of assessment, and the state of structure such as the imp ortance of the stru cture, the environment around the st ructure, and the type of loading.

Note: When it is difficult and/or unnecessary to investigate an entire structure, appropriate sections and/or locations should be identified for investigation

6.3.4 Selection of method

Appropriate methods are selected according to the item and the availability of measuring equipment, etc. The methods are classified into the following categories:

-- document search

-- inspection

-- visual observation

-- manipulation

-- non-destructive method

-- destructive method

-- testing

-- material testing

-- loading test for structure

The method shall be reviewed according to the changes in the category and the level of assessment.

6.3.5 Selection of tools and techniques

Tools and techniques used in each investigatio n method shall be appropriately chosen so that the desi red information on the deteri oration of mat erials and/or structural performance can be obtain ed. They shall be reviewed according to the result of investigation, the deterioration prediction, evaluation/judgment, and so on. Simultaneously, the inherent limitations of the tools and techniques in question shall be confirmed.

Note: The selection of tools/techniques also depends on the easin ess to access the local neede d to be investigated, the co sts and the availability of te sting equipment and expertise. When conducting investigations involving partially destructive testing, care should be taken not to damage the performance of the structure.

6.3.6 Frequency of investigation

The frequency of invest igation shall be ap propriately determined, d epending upon the cate gory of maintenance, the importance of the stru cture, the environment around the structure, the type of load acti on, etc.

6.3.7 Emergency measures after investigation

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When fatal defect or dam age of urgen cy is found durin g investigation, it shall be subje cted to emerge ncy measures because leaving such a defect or damage untreated may subsequently lead to a serious accident or a serious economic disadvantage. If unsafe conditions are observed, the qualified person is obligated to report them to authorities having jurisdiction.

6.3.8 Monitoring

Monitoring can continually record appropriate data for condition of a structure, so that appropriate remedial action can be taken before the deterioration becomes detrimental to the appearance and performance of the structure.

The most appropriate monitoring method shall be selected in consideration of the kind of information required, the availability of tools and equipment, and so on.

6.4 Prediction of deterioration and performance degradation of structure

6.4.1 Identification of deterioration mechanisms

To carry out app ropriate prediction of d eterioration occurring on the stru cture and/or its structu ral member under consideration, the mechanism of deterioration shall provisionally identified.

In general, deterioration mechanism should be identified in consideration of the deterioration factors specified and any signs of deterioration detected in the inspection and/or other tests in investigation.

Note: Deterioration factors may be classified as:

-- external fa ctors, i.e. those related to an externa l condition, such as environmental, weather, and external force conditions affecting the concrete structure under consideration;

-- internal factors, i.e. those related to the internal conditions of the structure and linked to the design and construction processes.

A structure and/or structural members are often subjected to more than one deterioration mechanism. In this case, the combined effects of those mechanisms shall be considered.

6.4.2 Determination of deterioration level and rate

According to the identifie d deterioration mechanism, current deterioration levels and rates on the structure and/or its members sh all be determined using appropriate analysis models established on the basis of the environmental conditions and any other useful information obtained from investigation.

Appropriate deterioration indices representing the deterioration condition of the structure and/or its members under consideration can be sel ected to simplif y modeling the deterioration and/or the perfo rmance degradation process.

6.4.3 Prediction of performance degradation of structure

The degradation in structural performance and its progress shall be properly predicted by appropriate models, which shall b e formulated based on the relationship between the stru cture/member’s performance and t he predicted level and rate of deterioration.

In principle, performance degradation predictions should be made quantitatively relating to all the performance requirements of the structure/members.

Note: For the structure’s performance, quantitative prediction is desirable, but this may be difficult in many cases. In such a case, the perform ance shall be eval uated by a “g rading method,” that is, th e structure’s performance is semi-quantitatively classified into grades.

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6.5 Evaluation and decision

6.5.1 Evaluation of performance of structure

6.5.1.1 Performance verification method

For evaluating structure/members condition, the performance possessed during intended service life, which is predicted in accordance with the specification in Clause 6.5.2, shall be verified with the threshold levels. The verification, in principle, should be carried out respectively for one or more of performance requirements.

Note: Provided that environmental and/or loading conditions are considered to be the same over time, the performance degradation of a structure over time may be evaluated by checki ng the performance at two points such as the time of an inspecti on and the end of intended service life. Howeve r, in general, the performance degradation process of the general structure is not in a simple monotonic process because environmental conditions can ch ange over shot periods of time . In such condition, the performance predictions based on two point s may result we ak and lead to insufficient conclusions about the performance of the structure.

6.5.1.2 Threshold levels for performance degradation of structure

The minimum level of accepta ble performance of the structure shall be dete rmined in accordance with each performance requirement, depending on the category of maintenance, importance and the conservation level of the structure.

6.5.1.3 Overall evaluation of performance level possessed

Performance possessed should be synthetically evaluated by confirming that each performance is verified to satisfy the required level.

6.5.2 Decision

Depending on the importance of the structu re, category of maintenance, intended remaining service life, life -cycle cost and other considerations, as well as the overall results of the structural performance assessment, decision shall be made ap propriately to give recommended actions in the prel iminary and detailed levels of assessment, respectively.

In the prelimi nary assessment level, d ecision should be m ade on the evalu ation of the structure/members condition as to whether a detailed assessment and/or remedial action is necessary.

In the detailed assessment level, decision should be made as to whether any remedial action is called for.

7. Remedial action

7.1 Selection of remedial action

The following alternatives shall be considered as the remedial action for a structure whose performance does not meet its requirement:

-- repair

-- strengthening

-- intensified inspection

-- restriction in service

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-- dismantling and removal, etc.

A suitable remedial action shall b e selected on the basis not only of the asse ssment results relating deterioration condition, structural integrity, and st ructural stability, etc., but also o n a comprehensive consideration of the following items:

-- category of maintenance

-- intended remaining service life

-- easiness of maintenance including cost efficiency

-- potential advantage of an earlier action from the aspect of life-cycle cost

-- importance of the structure

7.2 Repair

7.2.1 General

Repair including prevention measure (here-in-after referred to as “repair”) of a structure refers to the remedial action adopted for restoring structural performance up to the initially require d level by preventing or redu cing further deterioration, which includes repair of defective events such as cracks, removal of deterioration portion or deterioration factors, surface coating, etc.

Note: This standard clearly distinguishes “prevention” from “repair” in the definitions. However, both of them are the almost sa me manner in their metho ds and using materials. Therefore, the prevention measure of structure also should be executed on the provisions specified in Clause 7.2.

The procedure of repair mainly consists of planning, design, execution, and completion inspection.

Note: Planning and design of repair are covered in detailer by Part 3 of this standard, while details of execution and completion inspection of repair are covered by Part 4.

For execution of repair, appropriate steps shall be taken to ensure the use of proper materials and methods as well as being subjected to good quality control.

After the rep air is ta ken, the perfo rmance of the structure shall be evaluat ed by the a ssessment. The performance of the structure shall be upheld and a revised plan shall be developed.

7.2.2 Planning and design

7.2.2.1 Formulation of repair plan

Formulating a repair plan refers to establishing the requi red repair level set in accord ance with the specification in Clause 7.2.2.2, and se lecting a rep air method, repai r materials, sectional dimensions after repair, and execution methods.

7.2.2.2 Repair level

An appropriate repair level shall be set considering the maintenance category, the importance of the structure, intended remaining service life, cost effectiveness, and the post-repair maintenance plan.

Note: For instance, the repair level may be simply classified into the following three categories:

-- repair level expected to restore performance during intended remaining service life of stru cture by only one time of repair activity

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-- repair level expected to resto re structural performance during intended remaining service life o f structure by a few cycles of repair activity

-- repair level expected to restore structural performance by the several cycle s of repair activities, or to restore the performance only in the short period

7.2.2.3 Selection of methods and materials

The method and materials for repair shall be adequately chosen based on the dete rioration mechanism, intended remaining service life, the importance and maintenance level of the structure.

Note: Care should be taken, as the m ethod of re storing the pe rformance may vary depen ding on the deterioration mechanism, even if the level of performance degradation is the same.

7.2.2.4 Design of repair

A repair de sign should be executed after sel ecting the repair method, the material s used and the level of repair. In the repai r design, the types and combi nations of repair materials, execution methods, and repair area or portion should be determined.

7.2.3 Execution

7.2.3.1 Execution plan

Before execution of repair, a detailed execution pl an should be formulated in consideration of the execution environment, time of execution and execution period.

Repair shall be carried out with mini mum disturbance to the surrounding environment and the service condition of the structure.

7.2.3.2 Quality control in execution

The effectiveness of repair is strongly affected by the quality of execution. Therefore, the execution of repair shall be carried out under the sufficient quality control based on the prescribed execution plan.

During the execution of repair, necessary tests shall be carried out on the materials and other related control items.

Detailed quality control records during the execution of repair shall be maintained for future reference.

7.2.3.3 Completion investigation

After repair, completion investigation shall be carried out to e xamine the condition of material and the execution method carried out, thereby confirming that repair in accordance with the repair plan was executed, so that quality assurance shall be performed on all repairs to critical structural elements.

7.3 Other remedial actions

7.3.1 General

Not only repair but also strength ening, intensified inspection, restriction in service, and dismantling/rem oval may be taken as remedial action for existing structures, if necessary (see Clause 7.1). Only outline of each activity is prescribed in 7.3.2 to 7.3.5, respectively, though the details are omitted because application of these actions except of repair to structure is out of this standard.

7.3.2 Strengthening

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Strengthening of a st ructure refers to t he remedial action taken to upgrade structural performance to a l evel which is higher than that possessed at the original design.

An appropriate strengthening plan shall be formulated based on the target level of performance, then methods and materials for stren gthening shall be selecte d considering the degra dation condition of struct ural performance, deterioration mechanism, and maintenance after strengthening.

Note: Strengthening includes (a) increase in the cross-sectional area of concrete, (b) addition of members, (c) increase in the supporting points, (d) addition of strengthening members, (e) application of prestress, etc.

7.3.3 Intensified inspection

Intensified inspection refers to the remedial action carried out by increasing the inspection frequency, number of inspection items and/or location for inspection without any improvement of the c ondition or performance of structure in cases where repair or retrofit cannot be implemented immediately or where it is only req uired to keep the structure in present state

When intensifying inspection, the maintena nce plan should be revie wed considering the re sults of performance evaluation, remaining service life, importance of st ructure, cost for mainten ance, etc. and the n, appropriate inspection frequencies and items should be determined.

7.3.4 Restriction in service

Restriction in service may be effective for reduci ng damage to the stru cture. This may be achieve d by imposing restrictions on the usage, such as limiting the maximum live load that the structu re may carry. The degree and method of the restriction imposed on the usage shall be determined depending on the l evel of deterioration observed, so that su ch a rest riction shall be implemented after ca rrying out a d etailed assessment.

7.3.5 Dismantling and removal

Dismantling and removal of a severe ly deteriorated structure/member shall be carried out based on an implementation plan fo r the sel ected method which is formulated in co nsideration of threat posed to the environment, public safety and disposal of debris.

7.4 Special care for emergency

Where a structure is considered to be unsafe to the environm ent, its users or any third parties, app ropriate action shall be immediately implemented to make it safe before repair or other p reservation work is undertaken. In this process, any additio nal risks that may arise fro m the repair work itself shall be taken into account. Such actions may include local prote ction or re pair, the installation o f support or other tempo rary work, partial or even complete demolition.

In addition, plans for th e following remedial action shall be formulated on the ba sis of the exten t of deterioration, remaining service life, re maining and desired structural pe rformance for safety such as load bearing capacity, importance of the structure, the conservation level and previous remedial action taken.

8. Recording

8.1 General

Details concerning maintenance and repair shall be recorded. Such records as well as drawings and related documents shall be preserved by the owner for safe-keeping and future references.

8. 2 Period of preservation

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The maintenance records of a structure shall be pre served by the owner while the struct ure is in service. It is also desirable that such reco rds should be preserved for a period as required for reference purposes in the design, construction, and maintenance of other similar structures.

Note: It is expecte d that analysis of records can contribute to progress in maintenance technologies by clarifying problems and needed improvements in design and construction.

8.3 Method of recording

8.3.1 Format of records and its accessibility

The records shall be p reserved in an easily und erstandable format so that they can ea sily be referre d to. Since the record is preserved for a long time, much attention should be paid to make it be acce ssible even when the data recording and storing system is changed.

8.3.2 Items included in records

The records shall include the following items:

-- basic data concerning immediate and nearby environment, details of structure, the methods and results of deterioration prediction and investigation carried out, the result o f evaluation/judgment of the stru cture and photographs.

-- names of the persons responsible for maintenance

-- design drawings and specifications of construction

8.3.3 Records concerning remedial action

When remedial action is taken, records of the met hod used and details of execution shall be re corded together with the names of persons responsible for design, execution, and quality control of remedial actions.

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Annex A (informative)

Appendix to Maintenance and Repair of Concrete Structures – Part 1: General Principles –

A. Extended hierarchy of “Standards for maintenance and repair of concrete structures” with national legislation and other related ISO documents

Service life planning

(National)

Design of structures for durability

ISO 13823 (ISO TC 98/SC2)

Product 1 Product 2 Product N

Product and test standards



Part 2: Assessment of existing concrete structures ISO TC 71 / SC7

Part 3: Design of repair and preventionISO TC71 / SC7

Project WorkSpecification for pricing

and contract (National)


Technical Report: Assessment and repair of water leakage cracks

Technical Report: Seismic assessment and retrofit



Part 4: Execution of repair and prevention ISO TC71 / SC7



LAW and Regulations

ISO TC71 / SC7

Execution of concrete structures


ISO 15686-1 (ISO TC 59/SC14)

Assessment of existing structures


Execution of concrete structures


Performance and assessment requirements

ISO 19338(ISO TC 71/SC4)

Reliability for structures ISO 2394 (ISO TC 98/SC2)

Design of structures for durability


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Annex B (informative)


B. Hierarchy of terms

Maintenance plan

Assessment Testing

Prediction of performance

Investigation Inspection

Evaluation of performance

Decision making

Document search

Maintenance procedure

Record

Prevention Repair

Strengthening

Remedial action

Intensified inspection

Restriction in service

Dismantling and removal

Not covered by this standard in detail*

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Annex C (informative)


C. Category of maintenance

C1. General

Maintenance actions should be classified into differe nt categories depending on fa ctors such as the importance of the stru cture, design service life, safety risks concerns, environmental conditions, ease of maintenance, and cost. For example, importa nt structures such as dams and nuclear power plants hav e a long service life, and structures situated in very harsh environments (e.g. marine environment) may fall into a higher priority category than common structures such as multi-story buildings. Similarly, criteria for classifying structures into other pri ority levels need to be developed. Certain structu res for whi ch any speci al maintenance action (e.g. underground structures) may be classified separately.

Maintenance actions are classified as: preventive maintenance, corrective maintenance and observational maintenance.

C2. Preventive maintenance

Maintenance is conducted based on preventive preservation. Structures in this category generally have a high degree of importa nce, requiring monitoring in man y cases. Examples of structures requiring preventive maintenance are:

-- structures for whi ch remedial measures are difficu lt economically and/or technically to be taken after deterioration becomes apparent

-- structures whose deterioration must not be apparent, such as monuments

-- structures having a long intended remaining service life

C3. Corrective maintenance

Maintenance is conducted based on co rrective preservation. In this category, maintenance is conducted to restore deterioration level and/or reduce deterioration rate so as to make structural performance satisfactory in the intended remaining service life. Examples of structures requiring corrective maintenance are:

-- structures for which remedial measures can be taken after deterioration becomes apparent

-- structures for which apparent deterioration poses no immediate concern to the violation of performan ce requirements

C4. Observational maintenance

In this category, only visual inspections are conducted; no remedial action is undertaken regardless of the deterioration level. Maintenance activities for structures requiring observational maintenance are economically and/or technically difficult to perform. Examples of structures requiring observational maintenance are:

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-- structures for use as long as usable without any remedial actions except for the a ction to ensure safety from risks concerning due to falling debris and so on.

-- structures such as foundations, for which direct inspection is economically and/or technically difficult. The assessment and judgment can be made based on indirect inspection, such as land surveying, ground settlement measurement, and leakage detection, etc. Another option is constructing such structures in a way that a “maintenance free” condition is achieved.

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Annex D (informative)

Appendix to Maintenance and Repair of Concrete Structures

– Part 1: Framework and General Principles –

D. Category of assessment

D1. General

The maintenance procedure consists of various components: investigation, deterioration prediction, evaluation, judgment, remedial measures, and recording. In this International Standard, the set of activities to predi ct the structure’s condition, includes “investigation,” “deterioration prediction,” “evaluation” and “judgment,” is called as “assessment”.

The investigation in assessment is for collecting information on the perform ance of a structure. Based on the information provided by the investigati on, the pr ediction of deterioration ca n be made, followed by the evaluation of structural performance at present and in the future. The judg ment on whe ther the rem edial action would be necessary is finally made considering the evaluation results.

On the basis of the methods used, frequency and timing of assessment, and the type of information desired, the assessment is categorized as in itial, periodic and extraordinary assessment for fulfilling the assessm ent on a structure rationally and economically,

In each assessment, occurrence of deterioration and/or change in the performance of the structure should be detected through investigation. Obviously if undesi rable signs of deteri oration can be dete cted in the early stage of det erioration, suitable, timely remedial a ction can be taken. Actual locations in a structu re for investigation, tools used, items recorded, etc. should be carefully selected depending on the catego ry of assessment, so that the necessary information can be obtained reliably.

The relationship among initial, periodi c, and extraordi nary assessments in the framework of maintenan ce actions for concrete structures is shown in Fig.D1.

Include at the end of “General”

D2. Initial assessment

D2.1 General

Initial assessment is defin ed as an assessment carried out for evaluating t he initial condition of a struct ure before initiating into routine/regular maintenance activities.

Based on the results obtained in the initial assessment, the maintenance plan can be finally determined.

Information from the initial assessment can be used for subsequent planned periodic assessment as the initial information of structure.

Note: Investigation in i nitial assessment allows the collection of basic data for initiating a maintenance program. The major purp ose is to understan d the in itial condition related to the performan ce of th e structure. This is im portant from the a spect of d etecting initial de fects and/or damage and defining th e initial data for deterioration prediction.

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Fig.D1 Position of each assessment in maintenance flow

D2.2 Types of initial assessment

The following three types of assessment are regarded as the initial assessment:

-- assessment carried ou t before a ne wly constructed structure is put into op eration upon completion of construction

-- the first assessment of an existing structure carried out for the purpose of a maintenance activity

-- the first assessment of an existing structure which has been subjected to large-scale remedial actions and substantially renewed

D2.3 Method of investigation

Preliminary level of assessment

Extraordinaryassessment

Determination of Maintenance Plan

Initial assessment(If needed)

Provisional Setting of Maintenance Plan

Detailed level of assessment

Routine/regular assessment


Judgment for emergency measure

Need Emergency measures

No need

Judgment for detailed level of assessment

Need

Detailed level of assessment

No need

No need

Judgment for remedial action

Need

Remedial action


Periodic assessment

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As a first ste p of mainten ance procedure, it is ne cessary to col lect information on the structure by initial assessment. For a n ew structure, a p rovisional maintenance plan set in the design procedure should be revised based on the results in the “birth certificate.” On the other hand, for existing structures, the inspection should be carried out to collect information on the st ructure. Based on the information, the mainten ance plan can be finally determined.

One of the major aim s of the investigation in the initial assessme nt is to collect the information detectin g and documenting initial defects such as honeycombs, cold joint, sand streaking and so on, and some deterioration damage arising on the existing stru ctures before startin g maintenance activities. Therefore, when doing inspection, it should, in principle, be applied to the entire structure to check whether there are any defects or damages in the entire structure. However, when members of the structure located on the back of underground structures or under the foundation, the direct inspection to the members is difficult so that checking the design record and construction records should be base for the investigation.

The investigation should include not only obvious inspection of external appearance of structure but also the ones for fluctuation of con crete quality, existence of construction defects in concrete, co nstruction error on rebar arrangement, and so on.

D2.4 Records and storing of result

The results of initial assessment should be appropriately records, as they provi de useful data for the entire practice of maintenance.

D3 Periodic assessment

D3.1 General

After the ma intenance activities start on the struct ure, assessment of the structure should be fulfilled periodically at certain intervals according to a maintenance plan to evaluate the condition of the structure.

The aim of th e periodic assessment is to provide inf ormation regarding the condition of the structu re and its member under consideration, the causes for and the seriousness of any the deterioration. If necessarily, the investigation should be carried out to determine the current deterioration levels and rates, then, a ta rget reliability level that represents the required level of structural performance should be ensured.

The periodic assessment is further categorized into two ones, which are “routine assessment” and “regular assessment.”

D3.2 Routine assessment

D3.2.1 General

Routine assessment shall be carried out on a routin e basis at certain intervals mainly to detect the locati on and state of deteri oration by only simple investigat ion methods, such a s visual observati on and ham mer tapping, etc.

Routine assessment shall be fulfilled according to the maintenance plan. Normally, people having no spe cial knowledge about maintenance carry out it, so that a manual, which the maintena nce manager should formulate adequately, is required for maintaining the quality of assessment.

D3.2.2 Investigation in routine assessment

D3.2.2.1 Method

The methods of investig ation in rout ine assessment include visual inspections by visual ob servation, photographs, videos and binoculars, and inspection by hammer tapping which may sometimes be used. The

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visual observation is carried out for the whole of accessible parts, but hammer tapping is only carried out for a part capable of tapping.

The items checked by the investigation are as follows:

(i) cracking

(ii) delamination, peeling, spalling and scaling on the concrete surface

(iii) steel reinforcement exposure and corrosion

(iv) exudation of rust and efflorescence

(v) water leakage

(vi) any other discoloration

Investigation by driving feeling is also effective to inspect the drivi ng performance on bridges and other road structures, and could estimate abnormal displacement/deformation, abnormal sound/vibration and other conditions on expansion joint, extraordinary deflection and bumping.

D3.2.2.2 Location

The actual locations in a structure to be investigated in routine assessment should be basically those that can be inspected during routine patrol, but it is advisable that investigation should cover the locations as much as possible.

D3.2.3 Frequency of routine assessment

Routine assessment should be carried out frequently to confirm the absence of abnormality on the structure. The frequency should be appropriately determined in consideration of the workforce and/or budget, as well as the importance of the structure, the threat posed to third parties, and results of deterioration prediction.

D3.2.4 Records and storing of results

Routine assessment is frequently carried out, normally to confirm the absence of abnormality. Therefore, the record may be sufficient if the execution of inspect ion is indicat ed by the da te/time and the name of th e inspector. In a case when some abnormality is detected, however, the detected abnormal conditions should be added to the record in accordance with the manual for routine assessment.

D3.3 Regular assessment

D3.3.1 General

Regular assessment shall be carried out by using appropriate methods at regular intervals to observe closely on a whole of structure and to obtain more accurate information about signs of deterioration, which are difficult to gather during the routine inspection.

The items and frequency of the re gular assessment should be appropriately determined. These should be determined in consideration of the catego ry of maintenance, the relative importance of the stru cture and its members, past maintenance records, and results of deterioration prediction.

D3.3.2 Investigation in regular assessment

D3.3.2.1 Method

The investigation method in regular assessment should mainly be visual i nspection or hammer tapping. In general, scaffolding for investigation becomes necessary in re gular assessment since scaffolding permits close-range inspection, etc. Therefore, the inspection should be carried out not only by th e simple methods, but also by using some other techniques, such as non-destructive testing methods, core drilling, etc.

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The appropriate investigation methods used for the regular assessment shall be decided on the basis of such factors as the likely mech anism of deterio ration, environmental conditions, the impor tance of the structu re, and the category of maintenance.

D3.3.2.2 Location

The regular assessment basically should be carried out entirely on the structure. Careful investigation should be carried out for the l ocation of the structure where defects are difficult to be d etected during routine assessment. Sometimes, it is not easy to investigate large structures such as tunnel or viaduct entirely at one time. In this circumstance, it is possible to divide the location of investigation on the structure and inspect them in due orde r. Occasionally, it is advisable to decid e the order or se ction investigated in consideration of existing maintenance records, importance of parts/members, or cost efficiency.

D3.3.3 Frequency of regular assessment

The frequency of regular asse ssment, which is no rmally every two to ten years, shoul d be determin ed, in consideration of the re sults of dete rioration prediction, importance and types of the structure, intended remaining service life, en vironmental conditions, maintenance category, existing mainten ance records and cost efficiency.

D3.3.4 Records and storing of result

The regular assessment, which provides time series information of the structure, is useful for identifying th e progress of deterioration and confirming the validity of det erioration prediction. For this reason, it is important to maintain accurate records, such as t he inspection data, the na me of inspector, and detailed drawings of defects.

D4 Extraordinary assessment

D4.1 General

Natural disasters such as an earthquake, strong storm or flood, fire, impact by a vehicle or ship, and so on have strong impacts on st ructures, their members and parts. Therefore, extraordinary assessment shall be carried out after a stru cture has been subjected to such the a ccidental loads, to examine the extent of the damage and the need for a remedial action.

When an accident due to deterioration of a structure, such as falling concrete fragment, is found, extraordinary assessment also shall be ca rried out not only for the structure itself but also for the s imilar type structures to check if the similar accident may occur.

It is advisabl e to consi der carrying out extraordinary assessment in vi ew of maintenan ce category, the importance of the membe r/part of th e structure, structural performance, remaining service life an d cost efficiency.

D4.2 Investigation in extraordinary assessment

D4.2.1 Method

The purpose of investigation in extraordinary assessment is to grasp the state of the structure or its members after it is subjected to a disaster or accident. Detection of damages is particularly important.

Investigation shall be carried out closely to the structure to obtain more accurate information. The appropriate tools for the investigation shall be de cided on the bas is of su ch factors as the cau se and condition of damage/deterioration, environmental conditions, the rela tive importance of the structu re and category of maintenance level.

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Simple methods such as visual observation and hammer tapping are specified as the normal methods. Where instrumental inspection is relatively easily feasible a nd effective in detec ting damage or ot her events, it is advisable to carry out instrumental inspection, if necessary, in consideration of the cost efficiency and degree of emergency.

D4.2.2 Location

The range to be investigated is the me mber of the stru cture with the risk of d amage due to the disa ster or accident. The part under the ground or foundation is often subjected to the load of earthquake, and sometimes the damage might be difficult to investigate.

D4.3 Records and storing of results

Items to be recorded in extraordinary assessment should contain the de scription of the u nexpected event, purpose of inspection, the location and the con ditions of damage, and so on, in addition to those for regu lar assessment.

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Documents

[BS ISO 16311-1] -- Maintenance and repair of concrete structures. Part 1. General principles.pdf