ISO 13822:2001

INTERNATIONAL ISO
STANDARD 13822
First edition
2001-12-15
Corrected version
2003-02-15


Bases for design of structures —
Assessment of existing structures
Bases du calcul des constructions — Évaluation des constructions
existantes




Reference number
ISO 13822:2001(E)
©
 ISO 2001

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ISO 13822:2001(E)
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ISO 13822:2001(E)
Contents Page
Foreword . v
Introduction. vi
1 S . 1
2 Normative reference. 1
3 Terms and definitions. 2
4 General framework of assessment. 3
4.1 Objectives . 3
4.2 Procedure. 4
4.3 Specification of the assessment objectives. 5
4.4 Scenario . 5
4.5 Preliminary assessment . 5
4.6 Detailed assessment. 6
4.7 Results of assessment . 7
5 Data for assessment . 7
5.1 General . 7
5.2 Actions and environmental influences . 7
5.3 Material properties . 8
5.4 Properties of the structure . 8
5.5 Dimensions . 8
6 Structural analysis . 9
6.1 Models . 9
6.2 Limit states . 9
6.3 Basic variables . 9
6.4 Model uncertainties. 9
6.5 Conversion factors. 9
6.6 Uncertainty about the condition of components . 9
6.7 Deterioration models . 9
7 Verification. 10
7.1 Bases. 10
7.2 Reliability assessment. 10
7.3 Limit states . 10
7.4 Plausibility check . 10
7.5 Target reliability level. 10
8 Assessment based on satisfactory past performance. 10
8.1 Assessment of safety . 10
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ISO 13822:2001(E)
8.2 Assessment of serviceability. 11
9 Interventions. 11
10 Report . 11
10.1 General . 11
10.2 Conclusions . 11
10.3 Sufficient reliability . 11
10.4 Insufficient reliability . 11
10.5 Recommendations for interventions. 12
10.6 Inspection and maintenance plan. 12
10.7 Documented information. 12
10.8 Reporting style . 12
11 Judgement and decision . 12
11.1 Decision. 12
11.2 Change in use. 12
Annex A (informative) Hierarchy of terms . 13
Annex B (informative) General flowchart for assessment of existing structures . 14
Annex C (informative) Updating of measured quantities. 16
Annex D (informative) Testing for static and dynamic properties of structures. 21
Annex E (informative) Assessment of time-dependent reliability. 24
Annex F (informative) Target reliability level . 28
Annex G (informative) Report format. 30
Annex H (informative) Design of upgrading. 33
Bibliography. 35

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ISO 13822:2001(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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
Draft International Standards adopted by the technical committees are circulated to the member 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 possibility that some of the elements of this International Standard may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 13822 was prepared by Technical Committee ISO/TC 98, Bases for design of
structures, Subcommittee SC 2, Reliability of structures.
Annexes A to H of this International Standard are for information only.
This corrected version of ISO 13822:2001 incorporates the following corrections. The flowchart in Annex B has
been corrected and the year of publication of reference [8] in the Bibliography has been changed.
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ISO 13822:2001(E)
Introduction
The continued use of existing structures is of great importance because the built environment is a huge economic
and political asset, growing larger every year. The assessment of existing structures is now a major engineering
task. The structural engineer is increasingly called upon to devise ways for extending the life of structures whilst
observing tight cost constraints. The establishment of principles for the assessment of existing structures is needed
because it is based on an approach that is substantially different from the design of new structures, and requires
knowledge beyond the scope of design codes. This document is intended not only as a standard of principles and
procedures for the assessment of existing structures but also as a guide for use by structural engineers and clients.
Engineers can apply specific methods for assessment in order to save structures and to reduce a client's
expenditure. The ultimate goal is to limit construction intervention to a strict minimum, a goal that is clearly in
agreement with the principles of sustainable development.
The basis for the reliability assessment is contained in the performance requirements for safety and serviceability of
ISO 2394. Economic, social, and sustainability considerations, however, result in a greater differentiation in
structural reliability for the assessment of existing structures than for the design of new structures
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INTERNATIONAL STANDARD ISO 13822:2001(E)

Bases for design of structures — Assessment of existing
structures
1 Scope
1.1 This International Standard provides general requirements and procedures for the assessment of existing
structures (buildings, bridges, industrial structures, etc.) based on the principles of structural reliability and
consequences of failure. It is based on ISO 2394.
1.2 It is applicable to the assessment of any type of existing structure that was originally designed, analysed and
specified based on accepted engineering principles and/or design rules, as well as structures constructed on the
basis of good workmanship, historic experience and accepted professional practice. The assessment can be
initiated under the following circumstances:
 an anticipated change in use or extension of design working life;
 a reliability check (e.g. for earthquakes, increased traffic actions) as required by authorities, insurance
companies, owners, etc.;
 structural deterioration due to time-dependent actions (e.g. corrosion, fatigue);
 structural damage by accidental actions (see ISO 2394).
NOTE 1 This International Standard is applicable to historical structures, provided additional considerations are taken into
account concerning the preservation of the historical appearance of the structure and the preservation of its historical materials.
1.3 This International Standard is applicable to existing structures of any material, although specific adaptation
can be required depending on the type of material, such as concrete, steel, timber, masonry, etc.
1.4 This International Standard provides principles regarding actions and environmental influences. Further
detailed consideration will be necessary for accidental actions such as fire and earthquake.
NOTE 2 Fire resistance requires properties different from those for structural safety and integrity. Also fire hazards can be
created by change in use. Special requirements are necessary for seismic hazards, taking the dynamic action and structural
response into account.
1.5 This International Standard is intended to serve as a basis for preparing national standards or codes of
practice in accordance with current engineering practice and the economic conditions.
2 Normative reference
The following normative document contains provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent edition of the normative document indicated below. For
undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC
maintain registers of currently valid International Standards.
ISO 2394:1998, General principles on reliability for structures
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ISO 13822:2001(E)
3 Terms and definitions
For the purposes of this International Standard, the terms and definitions given in ISO 2394 and the following apply.
(See also annex A.)
3.1
assessment
set of activities performed in order to verify the reliability of an existing structure for future use
3.2
damage
unfavourable change in the condition of a structure that can affect structural performance
3.3
deterioration
process that adversely affects the structural performance, including reliability over time due to
 naturally occurring chemical, physical or biological actions,
 repeated actions such as those causing fatigue,
 normal or severe environmental influences,
 wear due to use, or
 improper operation and maintenance of the structure
3.4
deterioration model
mathematical model that describes structural performance as a function of time, taking deterioration into account
3.5
inspection
on-site non-destructive examination to establish the present condition of the structure
3.6
investigation
collection and evaluation of information through inspection, document search, load testing and other testing
3.7
load testing
test of the structure or part thereof by loading to evaluate its behaviour or properties, or to predict its load-bearing
capacity
3.8
maintenance
routine intervention to preserve appropriate structural performance
3.9
material properties
mechanical, physical or chemical properties of structural materials
3.10
monitoring
frequent or continuous, normally long-term, observation or measurement of structural conditions or actions
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ISO 13822:2001(E)
3.11
reference period
chosen period of time which is used as a basis for assessing values of variable actions, time-dependent material
properties, etc.
NOTE The remaining working life or the minimum standard period for safety of an existing structure can be taken as
reference period (see annex F).
3.12
rehabilitation
work required to repair, and possibly upgrade, an existing structure
3.13
remaining working life
period for which an existing structure is intended/expected to operate with planned maintenance
3.14
repair, verb
·of a structureÒ improve the condition of a structure by restoring or replacing existing components that have been
damaged
3.15
safety plan
plan specifying the performance objectives, the scenarios to be considered for the structure, and all present and
future measures (design, construction, or operation, such as monitoring) to ensure the safety of the structure
3.16
structural performance
qualitative or quantitative representation of the behaviour of a structure (e.g. load-bearing capacity, stiffness) in
terms of its safety and serviceability
3.17
target reliability level
level of reliability required to ensure acceptable safety and serviceability
3.18
upgrading
modifications to an existing structure to improve its structural performance
3.19
utilization plan
plan containing the intended use (or uses) of the structure, and listing the operational conditions of the structure
including maintenance requirements, and the corresponding performance requirements
4 General framework of assessment
4.1 Objectives
The objective of the assessment of an existing structure in terms of its required future structural performance shall
be specified in consultation with the client (the owner, the authority, insurance companies, etc.) based on the
following performance levels.
a) Safety performance level, which provides appropriate safety for the users of the structure.
b) Continued function performance level, which provides continued function for special structures such as
hospitals, communication buildings or key bridges, in the event of an earthquake, impact, or other foreseen
hazard.
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ISO 13822:2001(E)
c) Special performance requirements of the client related to property protection (economic loss) or serviceability.
The level of this performance is generally based on life cycle cost and special functional requirements.
4.2 Procedure
The assessment procedure is composed in general of the following steps so that the assessment is carried out
taking into account the actual conditions of the structures (see the flowchart in annex B). The procedure depends
on the assessment objectives (see 4.1), and on specific circumstances (e.g. the availability of the design
documents, the observation of damage, the use of the structure). A site visit is recommended prior to initiating the
procedure.
a) Specification of the assessment objectives.
b) Scenarios.
c) Preliminary assessment:
1) study of documents and other evidence;
2) preliminary inspection;
3) preliminary checks;
4) decisions on immediate actions;
5) recommendation for detailed assessment.
d) Detailed assessment:
1) detailed documentary search and review;
2) detailed inspection and material testing;
3) determination of actions;
4) determination of properties of the structure;
5) structural analysis;
6) verification.
e) Results of assessment:
1) report;
2) conceptual design of construction interventions;
3) control of risk.
f) Repeat the sequence if necessary.
The procedure outlined above may be applied to both the assessment of one specific structure and the assessment
of a group of structures.
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ISO 13822:2001(E)
4.3 Specification of the assessment objectives
At the outset, the objective of the assessment of the structure shall be clearly specified in terms of its future
performance in an agreement between the client, the authorities when relevant and the assessing engineer
(see 4.1). The required future performance shall be specified in the utilization plan and safety plan.
4.4 Scenario
Scenarios related to a change in structural conditions or actions should be specified in the safety plan in order to
identify possible critical situations for the structure. Each scenario is characterized by a predominant process or
action and, where appropriate, by one or more accompanying processes or actions. The identification of scenarios
represents the basis for the assessment and design of interventions to be taken to ensure structural safety and
serviceability.
4.5 Preliminary assessment
4.5.1 Study of documents and other evidence
Design and inspection documents contain important information that is necessary for a thorough assessment of an
existing structure. It shall be verified that the documents are correct, and that they are updated to include
information of any previous intervention to the structure. Other evidence, such as the occurrence of significant
environmental or seismic actions, large actions, changes in soil conditions, corrosion, and misuse of the structure,
shall be recorded and documented.
4.5.2 Preliminary inspection
The aim of a preliminary inspection is to identify the structural system and possible damage to the structure by
visual observation with simple tools. The information collected is related to aspects such as surface characteristics,
visible deformations, cracks, spalling, corrosion. The results of the preliminary inspection are expressed in terms of
a qualitative grading of structural conditions (e.g. none, minor, moderate, severe, destructive, unknown) for
possible damage.
4.5.3 Preliminary checks
The purpose of the preliminary checks is to identify the critical deficiencies related to the future safety and
serviceability of the structure with a view to focussing resources on these aspects in subsequent assessment.
Based on these results, it is then judged whether a further investigation is necessary or not.
4.5.4 Decisions on immediate actions
When the preliminary inspections and/or checks clearly indicate that the structure is in a dangerous condition, it is
necessary to report to the client that interventions should be taken immediately to reduce the danger with respect to
public safety. If there is uncertainty, the critical deficiencies should be assessed immediately and actions taken, if
necessary.
4.5.5 Recommendations for detailed assessment
The preliminary checks may clearly show the specific deficiencies of the structure, or that the structure is reliable
for its intended use over the remaining working life, in which case a detailed assessment is not required. Where
there is uncertainty in the actions, action effects or properties of the structure, a detailed assessment should be
recommended in accordance with 4.6.
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ISO 13822:2001(E)
4.6 Detailed assessment
4.6.1 Detailed documentary search and review
The following documents, if available, should be reviewed:
 drawings, specifications, structural calculations, construction records, inspection and maintenance records,
details of modifications;
 regulations and by-laws, codes of practice which were used for constructing the structure;
 topography, subsoil conditions, groundwater level at the site.
4.6.2 Detailed inspection and material testing
The details and dimensions of the structure as well as characteristic values of material properties can be obtained
from design documents, provided that the documents exist and that there is no reason for doubt. In case of any
doubts, the details and dimensions of components and properties of materials assumed for the analysis shall be
determined from a detailed inspection and material testing. The planning of such an inspection is based on
information that is already available. The detailed quantitative inspection will result in a set of updated values or
distributions for certain relevant parameters that affect the properties of the structure (see annex C).
4.6.3 Determination of actions
Actions and, in particular, environmental actions on structures shall be determined by analysis in accordance with
ISO 2394, taking into account provisions laid down in the safety and utilization plan.
4.6.4 Determination of properties of the structures
Testing of the structure is used to measure its properties and/or to predict the load-bearing capacity when other
approaches such as detailed structural analysis or inspection alone do not provide clear indication or have failed to
demonstrate adequate structural reliability (see annex D).
4.6.5 Structural analysis
Structural analysis in accordance with ISO 2394 shall be carried out to determine the effects of the actions on the
structure. The capacity of structural components to resist action effects shall also be determined. The deterioration
of an existing structure shall be taken into consideration. When deterioration of an existing structure is observed,
the reliability assessment of the structure becomes a time-dependent deterioration problem as described in
ISO 2394, and an appropriate analysis method shall be used. In the case of deteriorated structures, it is essential
to understand the causes for the observed damage or misbehaviour.
Some examples of appropriate analysis methods to assess time-dependent reliability can be found in annex E.
NOTE For deterioration, it is often more practical to use service-life predictors (such as S-N curves for fatigue or time-to
spalling models for corrosion of reinforcement) based on test data.
4.6.6 Verification
The verification of an existing structure should normally be carried out to ensure a target reliability level that
represents the required level of structural performance (see 4.1 and annex F). Current codes or codes equivalent to
ISO 2394 which have produced sufficient reliability over a long period of application may be used. Former codes
that were valid at the time of construction of an existing structure should be used as informative documents.
Alternatively, verification may be based on satisfactory past performance (see clause 8).
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