Guidelines for simplified seismic assessment and rehabilitation of concrete buildings

The purpose of ISO 28841:2013 is to provide sufficient information to perform the seismic assessment and rehabilitation of the structural concrete building that complies with the limitations established in ISO 28841:2013, for both undamaged structures that are deemed not to comply with the required characteristics for an adequate response at a specified performance level, and for structures that have undergone damage under seismic loadings. The rules of design as set forth in ISO 28841:2013 are simplifications of more elaborate requirements. ISO 28841:2013 can be used as an alternative to the development of a building code, or equivalent document in countries where no national design codes are available by themselves, or as an alternative to the building code in countries where specifically considered and accepted by the national standards body or other appropriate regulatory organization, and applies to the assessment of earthquake resistance capability and to the seismic rehabilitation design and construction for existing structural concrete buildings.

Lignes directrices pour l'évaluation sismique simplifiée et la réhabilitation des structures en béton

Smernice za poenostavljene ocene potresne varnosti in sanacijo betonskih zgradb

General Information

Status
Published
Publication Date
21-May-2013
Current Stage
6060 - International Standard published
Start Date
21-Mar-2013
Completion Date
22-May-2013

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INTERNATIONAL ISO
STANDARD 28841
First edition
2013-06-01
Guidelines for simplified seismic
assessment and rehabilitation of
concrete buildings
Lignes directrices pour l'évaluation sismique simplifiée et la
réhabilitation des structures en béton
Reference number
ISO 28841:2013(E)
ISO 2013
---------------------- Page: 1 ----------------------
ISO 28841:2013(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2013

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,

electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or

ISO's member body in the country of the requester.
ISO copyright office
Case postale 56  CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
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Published in Switzerland
ii © ISO 2013 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 28841:2013(E)
Contents Page

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

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

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

2  Normative references ............................................................................................................................ 1

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

4  Symbols and abbreviated terms ........................................................................................................ 13

5  Limitations ........................................................................................................................................... 17

5.1  Occupancy ........................................................................................................................................... 17

5.2  Maximum number of stories .............................................................................................................. 18

5.3  Maximum aspect ratios ....................................................................................................................... 18

5.4  Maximum story height ........................................................................................................................ 18

5.5  Maximum difference in story height .................................................................................................. 18

5.6  Maximum difference in floor area ...................................................................................................... 18

5.7  Maximum difference in story mass ................................................................................................... 18

5.8  Maximum column offset ..................................................................................................................... 18

5.9  Maximum span length ......................................................................................................................... 18

5.10  Maximum difference in span length .................................................................................................. 18

5.11  Maximum cantilever span ................................................................................................................... 18

5.12  Maximum slope for slabs, girders, beams and joists ...................................................................... 19

5.13  Maximum slope of the terrain ............................................................................................................ 19

5.14  Distance between center of mass and center of rigidity ................................................................. 19

6  Assessment and rehabilitation procedure........................................................................................ 19

6.1  Procedure outline ................................................................................................................................ 19

6.2  Data collection ..................................................................................................................................... 20

6.3  Lateral load resisting system classification ..................................................................................... 21

6.4  Material assessment ........................................................................................................................... 21

6.5  Condition assessment ........................................................................................................................ 21

6.6  Structural assessment ........................................................................................................................ 21

6.7  Rehabilitation design .......................................................................................................................... 21

6.8  Rehabilitation construction ................................................................................................................ 21

6.9  Design documentation ........................................................................................................................ 21

7  General Guides .................................................................................................................................... 23

7.1  Limit states ........................................................................................................................................... 23

7.2  Ultimate limit state design format ...................................................................................................... 23

7.3  Serviceability limit state design format ............................................................................................. 24

8  Classification of the structure system of the building .................................................................... 24

8.1  Concrete frame systems ..................................................................................................................... 24

8.2  Concrete wall systems ........................................................................................................................ 24

8.3  Concrete dual systems ....................................................................................................................... 25

9  Condition assessment of structures damaged by a seismic event ............................................... 25

9.1  Material assessment ........................................................................................................................... 25

9.2  Condition Assessment ........................................................................................................................ 28

9.3  Structural assessment ........................................................................................................................ 41

9.4  Final assessment ................................................................................................................................. 41

10  Condition assessment of existing structures .................................................................................. 41

10.1  Vulnerability level ................................................................................................................................ 41

10.2  Actual condition of the structure ....................................................................................................... 42

© ISO 2013 – All rights reserved iii
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ISO 28841:2013(E)

10.3  Seismic hazard ..................................................................................................................................... 43

10.4  Architectural layout ............................................................................................................................. 45

10.5  Foundation ........................................................................................................................................... 50

10.6  Soil type ................................................................................................................................................ 50

10.7  Quality aspects .................................................................................................................................... 50

10.8  Structural assessment ........................................................................................................................ 51

10.9  Final assessment ................................................................................................................................. 52

11  Rehabilitation analysis and design .................................................................................................... 54

11.1  Concrete Frame Systems .................................................................................................................... 54

11.2  Concrete wall systems ........................................................................................................................ 54

11.3  Concrete frames with concrete infills ................................................................................................ 55

11.4  Foundation rehabilitation .................................................................................................................... 55

11.5  Rehabilitation Measures for the structural system .......................................................................... 55

12  Rehabilitation construction ................................................................................................................ 57

12.1  Demolitions and debris retrieval ........................................................................................................ 57

12.2  Cover retrieval ...................................................................................................................................... 57

12.3  Surface preparations ........................................................................................................................... 57

12.4  Adherence concerns ........................................................................................................................... 58

12.5  Durability concerns ............................................................................................................................. 58

Annex A (normative) Structural Assessment ................................................................................................. 59

A.1  Resistance ............................................................................................................................................ 59

A.2  Story drift .............................................................................................................................................. 63

A.3  Energy dissipation level ...................................................................................................................... 65

A.4  Equivalent equations for material factors ......................................................................................... 69

A.5  Equivalent equations for material factors ......................................................................................... 73

Bibliography ...................................................................................................................................................... 76

iv © ISO 2013 – All rights reserved
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ISO 28841:2013(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. 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. 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.

The committee responsible for this document is ISO/TC 71, Concrete, reinforced concrete and pre-stressed

concrete, Subcommittee SC 5, Simplified design standard for concrete structures.
© ISO 2013 – All rights reserved v
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ISO 28841:2013(E)
Introduction

The aim of this International Standard is to provide rules for the earthquake resistant assessment and

rehabilitation design and execution for existing structural concrete buildings for which simplified procedures

may be applied instead of more sophisticated and thorough analyses, in light of the simplicity, symmetry, and

other characteristics of the structure under study. This International Standard is developed for countries that

do not have existing national standards on this subject and to offer, to local regulatory authorities anywhere,

an alternative for the study of relatively small and simple buildings that abound in both rural and urban

environments. The analysis and design rules are based in simplified worldwide-accepted strength models.

This International Standard is self-contained; therefore actions (loads), simplified analysis procedures and

design specifications are included, as well as minimum acceptable construction practice guidelines.

The minimum dimensional guidelines contained in this International Standard are intended to account for

undesirable side effects that will otherwise require more sophisticated analysis and design procedures.

Material and construction guidelines are aimed at site-mixed concrete as well as ready-mixed concrete, and

steel of the minimum available strength grades.

The earthquake resistance guidelines are included for rehabilitation of concrete buildings in the numerous

regions of the world which lie in earthquake prone areas. The earthquake resistance of rehabilitated buildings

is based upon the employment of structural concrete walls (shear walls) that limit the lateral deformations of

the structure and provide for its lateral strength.

This International Standard contains guidelines that can be modified by the national standards body due to

local design and construction requirements and practices. These guidelines that can be modified are included

using ["boxed values"]. The authorities in each member country are expected to review the "boxed values"

and may substitute alternative definitive values for these elements for use in the national application of this

International Standard. Changes to boxed values shall not be made without thorough analyses and sound

supporting studies.

A great effort was made to include self-explanatory tables, graphics, and design aids to simplify the use of this

International Standard and provide foolproof procedures. Notwithstanding, the economic implications of the

conservatism inherent in approximate procedures as a substitute for sound and experienced engineering

should be a matter of concern to the designer that employs the document, and to the owner that hires him.

vi © ISO 2013 – All rights reserved
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INTERNATIONAL STANDARD ISO 28841:2013(E)
Guidelines for simplified seismic assessment and rehabilitation
of concrete buildings
1 Scope

This International Standard can be used as an alternative to the development of a building code, or equivalent

document in countries where no national design codes are available by themselves, or as an alternative to the

building code in countries where specifically considered and accepted by the national standards body or other

appropriate regulatory organization, and applies to the assessment of earthquake resistance capability and to

the seismic rehabilitation design and construction for existing structural concrete buildings.

The purpose of these guidelines is to provide sufficient information to perform the seismic assessment and

rehabilitation of the structural concrete building that complies with the limitations established in Clause 5, for

both undamaged structures that are deemed not to comply with the required characteristics for an adequate

response at a specified performance level, and for structures that have undergone damage under seismic

loadings. The rules of design as set forth in this International Standard are simplifications of more elaborate

requirements.

Although the guidelines contained in this International Standard were drawn to produce, when properly

employed, a reasonable assessment of the seismic vulnerability of an undamaged structure, a reasonable

assessment of a structure damaged by a seismic event and a structural rehabilitation of the assessed

concrete structure with an appropriate margin of safety, these guidelines are not a replacement for sound and

experienced engineering. In order to attain the intended results on assessment and rehabilitation design, this

International Standard must be used as a whole, and alternative procedures should be employed only when

explicitly permitted by the guidelines. The minimum dimensioning guides as prescribed in this International

Standard replace, in most cases, more elaborate procedures such as those prescribed in the national code or,

if no national code exists, in internationally recognized full fledged codes, and the possible economic impact is

compensated for by the simplicity of the procedures prescribed here.

The professional applying the procedures set forth by these guidelines should meet the legal requirements for

structural designers in the country of adoption and have training and a minimum appropriate knowledge of

structural mechanics, statics, strength of materials, structural analysis, and reinforced concrete design and

construction.

While buildings rehabilitated in accordance with these guidelines are expected to perform within the selected

performance levels for the applicable design earthquakes, compliance with these guidelines is necessary but

may not guarantee the sought for performance, as current knowledge of structural behavior under seismic

loads, and of the loads themselves, is still incomplete.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated references,

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

ISO 15673:2005, Guidelines for the simplified design of structural reinforced concrete for buildings

© ISO 2013 – All rights reserved 1
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ISO 28841:2013(E)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
acceleration of gravity, g
acceleration produced by gravity at the surface of the earth

NOTE For the application of these guidelines its value can be approximated to 10 m/s .

3.2
adherence
force acting on the interface of two solid materials
3.3
admixture

material other than water, aggregate, or hydraulic cement, added to concrete before or during its mixing to

modify its properties
3.4
aggregate

granular material, such as sand, gravel, crushed stone, and iron blast-furnace slag, used in conjunction with

cementitious materials to form a hydraulic cement concrete or mortar
3.5
anchorage
devices used to anchor a non-structural element to the structural framing
3.6
bar diameter, nominal

approximate diameter of a steel reinforcing bar, often used as a class designation

NOTE For deformed bars, it is common practice to use the diameter of a plain bar having the same area.

3.7
beam

structural member for which ratio of axial load to axial gross capacity is equal to or less than 0,1.

3.8
bearing capacity of the soil

maximum permissible stress on the foundation soil that provides adequate safety against bearing failure of the

soil
NOTE Its value is defined at the working stress level.
3.9
bending moment

product of a force and the distance to a particular axis, producing bending effects in a structural element

3.10
boundary elements

structural elements embedded at the ends of structural walls strengthened by transverse reinforcement to

confine the longitudinal reinforcement
NOTE Boundary elements may require an increase in thickness of the wall.
2 © ISO 2013 – All rights reserved
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ISO 28841:2013(E)
3.11
caisson

foundation pile of large diameter, built partly or totally above ground and sunk below ground usually by digging

out the soil inside
3.12
carbonation

process of conversion of calcium hydroxide in hardened cementitious material into calcium carbonate due to

reaction with carbon dioxide diffused into the cement paste from the atmosphere
3.13
cement

material as specified in the corresponding referenced ISO standards, which, when mixed with water, has

hardening properties
3.14
center of mass

geometric plan location of the resultant force due to the action of gravity on the mass of the floor is located,

supposing the floor diaphragm as an infinite rigid body in its own plane
3.15
center of rigidity

geometric plan location of the resultant of the resistance forces due to structural vertical elements stiffness,

calculated, supposing that the floor diaphragm is an infinite rigid body in its own plane in such a way that when

applying a horizontal force in any direction, rotation of the diaphragm takes place with no distortion of the

original shape of the floor
3.16
corrosion

process of disintegration of the reinforcing steel bars due to chemical or electromechanical change caused in

presence of moisture
3.17
column

structural member in which the ratio of axial compressive loads to axial gross capacity is more than 0,1

3.18
collector elements

structural elements that carry the forces within a horizontal diaphragm to the lateral-force resisting system

3.19
combined footing

footing that transmits to the supporting soil the load carried by several columns or structural concrete walls

3.20
compression reinforcement
reinforcement provided to resist compression stresses in the member section
3.21
concrete

mixture of cementitious materials with fine aggregate, coarse aggregate, and water, with or without admixtures,

to form a hardened material with specific strength properties
3.22
concrete mix design
choice and proportioning of the ingredients of concrete
© ISO 2013 – All rights reserved 3
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ISO 28841:2013(E)
3.23
concrete specified compressive strength, f

compressive strength of cylindrical concrete specimens used in design and evaluated in accordance with the

appropriate ISO standard, expressed in megapascals (MPa)
' '

NOTE Whenever the quantity f is under a radical sign ( f ), the positive square root of numerical value only is

c c
intended, and the corresponding result has units of megapascals (MPa).
3.24
confinement hook

hook at the ends of a stirrup, hoop, or crosstie having a bend of not less than 135° with a six-diameter (but not

less than 75 mm) extension that engages the longitudinal reinforcement and projects into the interior of the

stirrup, hoop or crosstie
3.25
confinement stirrup or tie
closed stirrup, tie or continuously wound spiral

NOTE A closed stirrup or tie can be made up of several reinforcement elements each having confinement hooks at

both ends. A continuously wound spiral should have a confinement hook at both ends.

3.26
cover, concrete

thickness of concrete between the surface of any reinforcing bar and the nearest face of the concrete member

3.27
crack

break, with or without quite separating in two parts, of concrete, usually near or at the surface

3.28
creep

unrecoverable strain caused to a material subjected to constant stress for a long duration

3.29
crosstie

continuous reinforcing bar having a 135° hook at one end and a hook not less than 90° at least a six-diameter

extension at the other end

NOTE The hooks should engage peripheral longitudinal bars. The 90° hooks of two successive crossties engaging

the same longitudinal bars should be alternated end for end.
3.30
curing

process in which concrete is kept damp for a period of several days, starting from the moment it is cast, in

order to prevent evaporation of water within the cementitious paste to ensure that the hardening process

attains the intended strength

NOTE Appropriate curing will greatly reduce shrinkage, increase strength of concrete, and should reduce surface

cracking. Curing time will depend on temperature and relative humidity of surrounding air, the amount of wind, the direct

sunlight exposure, the type of concrete mix employed, and other factors.
3.31
dead load
permanent load
load in which variations over time are rare or of small magnitude
NOTE All other loads are variable loads (see also nominal loads).
4 © ISO 2013 – All rights reserved
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ISO 28841:2013(E)
3.32
deformed reinforcement

steel reinforcement that has deformations in its surface to increase its bond to the concrete

NOTE The following steel reinforcement should be considered deformed reinforcement under these guidelines:

deformed reinforcing bars, deformed wire, welded plain wire fabric, and welded deformed wire fabric conforming to the

appropriate ISO standards.
3.33
depth of member, h

vertical dimension of a cross section of a horizontal structural element or cross section dimension parallel to

the direction of transversally applied loads to vertical structural elements
3.34
design load combinations
combinations of factored loads and forces as specified in these guidelines
3.35
design strength
product of the nominal strength and a strength reduction factor 
3.36
development length

length of embedded reinforcement required to develop the design strength of reinforcement at a critical

section
3.37
development length for a bar with a standard hook

minimum length to be provided between the critical section (where the strength of the bar is to be developed)

and a tangent to the outer edge of the 90° or 180° hook
3.38
differential settlement
non-uniform vertical displacement of the foundation
3.39
drift
difference between the horizontal displacements of two floor levels
3.40
durability

characteristics of a structure to resist gradual degradation of its serviceability in a given environment for the

design service life
3.41
effective depth of section, d

distance measured from extreme compression fiber to centroid of tension reinforcement

3.42
embedment length
length of embedded reinforcement provided beyond a critical section
3.43
fatigue
weakening of a material by load cycles, with or without load reversals
3.44
factored loads and forces

specified nominal loads and forces multiplied by the load factors prescribed in these guidelines

© ISO 2013 – All rights reserved 5
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ISO 28841:2013(E)
3.45
fire protection of reinforcement

amount of concrete cover necessary for protection of the reinforcement against the effects of the high

temperatures produced by fire

NOTE The concrete cover is a function of specified fire resistance, measured in hours.

3.46
flange
top or bottom part of an “I” or “T” shaped section
3.47
flexural
pertaining to the effect of flexure
3.48
flexural reinforcement

reinforcement provided to resist the tensile stresses induced by flexural moments acting on the member

section
3.49
footing
that portion of the foundation which transmits loads directly to the soil

NOTE May be the widening part of a column, a structural concrete wall or several columns, in a combined footing.

3.50
formwork

temporary construction to contain concrete in a plastic state while it is cast and setting, and which provides the

final shape of the element as the concrete hardens
3.51
foundation
part of the structure that transmits loads to the underlying
...

SLOVENSKI STANDARD
oSIST ISO/DIS 28841:2010
01-november-2010
Smernice za poenostavljene ocene potresne varnosti in sanacijo betonskih
zgradb

Guidelines for simplified seismic assessment and rehabilitation of concrete buildings

Norme pour l'évaluation sismique simplifiée et la réhabilitation des structures en béton

Ta slovenski standard je istoveten z: ISO/DIS 28841
ICS:
91.080.40 Betonske konstrukcije Concrete structures
91.120.25 =DãþLWDSUHGSRWUHVLLQ Seismic and vibration
YLEUDFLMDPL protection
oSIST ISO/DIS 28841:2010 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
oSIST ISO/DIS 28841:2010
---------------------- Page: 2 ----------------------
oSIST ISO/DIS 28841:2010
DRAFT INTERNATIONAL STANDARD ISO/DIS 28841
ISO/TC 71/SC 5 Secretariat: ICONTEC
Voting begins on: Voting terminates on:
2010-06-15 2010-11-15

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

Guidelines for simplified seismic assessment and rehabilitation
of concrete buildings

Norme pour l'évaluation sismique simplifiée et la réhabilitation des structures en béton

ICS 91.080.40

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.

THIS DOCUMENT IS A DRAFT CIRCULATED FOR COMMENT AND APPROVAL. IT IS THEREFORE SUBJECT TO CHANGE AND MAY NOT BE

REFERRED TO AS AN INTERNATIONAL STANDARD UNTIL PUBLISHED AS SUCH.

IN ADDITION TO THEIR EVALUATION AS BEING ACCEPTABLE FOR INDUSTRIAL, TECHNOLOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT

INTERNATIONAL STANDARDS MAY ON OCCASION HAVE TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL TO BECOME STANDARDS TO

WHICH REFERENCE MAY BE MADE IN NATIONAL REGULATIONS.

RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT, WITH THEIR COMMENTS, NOTIFICATION OF ANY RELEVANT PATENT RIGHTS OF WHICH

THEY ARE AWARE AND TO PROVIDE SUPPORTING DOCUMENTATION.
International Organization for Standardization, 2010
---------------------- Page: 3 ----------------------
oSIST ISO/DIS 28841:2010
ISO/DIS 28841
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ii ISO 2010 – All rights reserved
---------------------- Page: 4 ----------------------
oSIST ISO/DIS 28841:2010
ISO/DIS 28841
Contents Page

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

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

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

2 Normative references............................................................................................................................1

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

4 Symbols (and abbreviated terms)......................................................................................................13

5 Limitations ...........................................................................................................................................23

5.1 Occupancy ...........................................................................................................................................23

5.1.1 Permitted occupancy ..........................................................................................................................23

5.1.2 Mixed occupancy.................................................................................................................................24

5.2 Maximum number of stories ..............................................................................................................24

5.3 Maximum aspect ratios.......................................................................................................................24

5.4 Maximum story height ........................................................................................................................24

5.5 Maximum span length.........................................................................................................................25

5.6 Maximum difference in span length ..................................................................................................25

5.7 Maximum cantilever span...................................................................................................................25

5.8 Maximum slope for slabs, girders, beams and joists......................................................................25

5.9 Maximum slope of the terrain ............................................................................................................25

5.10 Distance between center of mass and center of rigidity.................................................................25

6 Assessment and rehabilitation procedure........................................................................................26

6.1 Procedure outline................................................................................................................................26

6.2 Data collection.....................................................................................................................................27

6.3 Lateral load resisting system classification.....................................................................................27

6.4 Material assessment ...........................................................................................................................27

6.5 Condition assessment ........................................................................................................................27

6.6 Structural assessment........................................................................................................................27

6.7 Rehabilitation design ..........................................................................................................................27

6.8 Rehabilitation construction................................................................................................................27

6.9 Design documentation........................................................................................................................28

6.9.1 Assessment record .............................................................................................................................28

6.9.2 Rehabilitation calculation memoir.....................................................................................................28

6.9.3 Geotechnical report.............................................................................................................................28

6.9.4 Structural drawings.............................................................................................................................28

6.9.5 Specifications ......................................................................................................................................29

7 General Guides....................................................................................................................................29

7.1 Limit states...........................................................................................................................................29

7.2 Ultimate limit state design format......................................................................................................29

7.2.1 General .................................................................................................................................................29

7.2.2 Required factored strength ................................................................................................................30

7.3 Serviceability limit state design format.............................................................................................30

8 Classification of the structure system of the building ....................................................................31

8.1 Concrete frame systems.....................................................................................................................31

8.2 Concrete wall systems........................................................................................................................31

8.3 Concrete dual systems .......................................................................................................................31

9 Condition assessment of structures damaged by a seismic event ...............................................32

9.1 Material assessment ...........................................................................................................................32

9.1.1 Material properties ..............................................................................................................................33

© ISO 2009 – All rights reserved iii
DRAFT 2010
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oSIST ISO/DIS 28841:2010
ISO/DIS 28841

9.1.2 Component properties ....................................................................................................................... 33

9.1.3 Test methods....................................................................................................................................... 34

9.1.4 Minimum number of tests .................................................................................................................. 34

9.1.5 Soundness........................................................................................................................................... 35

9.2 Condition Assessment....................................................................................................................... 35

9.2.1 Layout of structural damages ........................................................................................................... 35

9.2.2 Damage levels..................................................................................................................................... 37

9.2.3 Layout of non structural damages.................................................................................................... 50

9.3 Structural assessment ....................................................................................................................... 51

9.4 Final assessment................................................................................................................................ 51

10 Condition assessment of existing structures..................................................................................51

10.1 Vulnerability level ............................................................................................................................... 52

10.2 Actual condition of the structure ...................................................................................................... 52

10.3 Seismic hazard.................................................................................................................................... 53

10.3.1 No seismic hazard zones ................................................................................................................... 56

10.3.2 Low seismic hazard zones................................................................................................................. 56

10.3.3 Intermediate seismic hazard zones .................................................................................................. 56

10.3.4 High seismic hazard zones................................................................................................................ 56

10.4 Architectural layout ............................................................................................................................ 56

10.4.1 Plan irregularity................................................................................................................................... 56

10.4.2 Elevation irregularity .......................................................................................................................... 58

10.5 Foundation .......................................................................................................................................... 61

10.6 Soil type ............................................................................................................................................... 61

10.7 Quality aspects ................................................................................................................................... 61

10.7.1 Quality of design................................................................................................................................. 61

10.7.2 Quality of materials ............................................................................................................................ 62

10.7.3 Quality of construction ...................................................................................................................... 62

10.7.4 Non structural elements..................................................................................................................... 62

10.8 Structural assessment ....................................................................................................................... 62

10.9 Final assessment................................................................................................................................ 63

11 Rehabilitation analysis and design................................................................................................... 65

11.1 Concrete Frame Systems................................................................................................................... 65

11.2 Concrete wall systems ....................................................................................................................... 65

11.3 Concrete frames with concrete infills............................................................................................... 65

11.4 Foundation rehabilitation................................................................................................................... 65

11.5 Rehabilitation Measures for the structural system......................................................................... 66

11.5.1 Reinforced concrete jacketing .......................................................................................................... 66

11.5.2 Shotcreting.......................................................................................................................................... 66

11.5.3 FRP reinforcements............................................................................................................................ 67

12 Rehabilitation construction ............................................................................................................... 68

12.1 Demolitions and debris retrieval....................................................................................................... 68

12.2 Cover retrieval..................................................................................................................................... 68

12.3 Surface preparations.......................................................................................................................... 68

12.4 Adherence concerns .......................................................................................................................... 68

12.5 Durability concerns ............................................................................................................................ 69

Bibliography..................................................................................................................................................... 70

Annex A (Normative) Structural Assessment.............................................................................................. 71

A.1 Resistance........................................................................................................................................... 71

A.1.1 Design strength for flexure only ....................................................................................................... 71

A.1.2 Design strength for axial compression ............................................................................................ 72

A.1.3 Balanced strength for axial compression with flexure................................................................... 72

A.1.4 Design strength for axial tension without flexure........................................................................... 73

A.1.5 Minimum design combined axial load and moment strength........................................................ 73

A.2 Flexibility ............................................................................................................................................. 75

A.3 Energy dissipation level..................................................................................................................... 76

A.3.1 Required energy dissipation level .................................................................................................... 76

© ISO 2009 – All rights reserved
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oSIST ISO/DIS 28841:2010
ISO/DIS 28841
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 2.

The main task of technical committees is to prepare International Standards. 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 document may be the subject of patent

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

ISO 28841 was prepared by Technical Committee ISO/TC 71, Concrete, reinforced concrete and pre-stressed

concrete, Subcommittee SC 05, Simplified design standard for concrete structures.

© ISO 2009 – All rights reserved v
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oSIST ISO/DIS 28841:2010
ISO/DIS 28841
Introduction

The aim of these International Guidelines is to provide rules for the earthquake resistant assessment and

rehabilitation design and execution for existing structural concrete buildings for which simplified procedures

may be applied instead of more sophisticated and thorough analyses, in light of the simplicity, symmetry, and

other characteristics of the structure under study. This document is developed for countries that do not have

existing national standards on this subject and to offer, to local regulatory authorities anywhere, an alternative

for the study of relatively small and simple buildings that abound in both rural and urban environments. The

analysis and design rules are based in simplified worldwide-accepted strength models. The document is self-

contained; therefore actions (loads), simplified analysis procedures and design specifications are included, as

well as minimum acceptable construction practice guidelines.

The minimum dimensional guidelines contained in this document are intended to account for undesirable side

effects that will otherwise require more sophisticated analysis and design procedures. Material and

construction guidelines are aimed at site mixed concrete as well as ready-mixed concrete, and steel of the

minimum available strength grades.

The earthquake resistance guidelines are included for rehabilitation of concrete buildings in the numerous

regions of the world which lay in earthquake prone areas. The earthquake resistance of rehabilitated buildings

is based upon the employment of structural concrete walls (shear walls) that limit the lateral deformations of

the structure and provide for its lateral strength.

The document contains guidelines that can be modified by the national standards body due to local design

and construction requirements and practices. These guidelines that can be modified are included using

["boxed values"]. The authorities in each member country are expected to review the "boxed values" and may

substitute alternative definitive values for these elements for use in the national application of the document.

A great effort was made to include self-explanatory tables, graphics, and design aids to simplify the use of the

document and provide foolproof procedures. Notwithstanding, the economic implications of the conservatism

inherent in approximate procedures as a substitution to sound and experienced engineering should be a

matter of concern to the designer that employs the document, and to the owner that hires him.

© ISO 2009 – All rights reserved
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oSIST ISO/DIS 28841:2010
ISO/DIS 28841
Guidelines for simplified seismic assessment and rehabilitation
of concrete buildings
1 Scope

This document can be permitted to be used as an alternative to the development of a building code, or

equivalent document in countries where no national design codes are available by themselves, or as

an alternative to the building code in countries where specifically considered and accepted by the

national standards body or other appropriate regulatory organization, and applies to the assessment of

earthquake resistance capability and to the seismic rehabilitation design and construction for existing

structural concrete buildings.

The purpose of these guidelines is to provide a registered civil engineer with sufficient information to

perform the seismic assessment and rehabilitation of the structural concrete building that complies with

the limitations established in 5., for both undamaged structures that are deemed not to comply with the

required characteristics for an adequate response at a specified performance level, and for structures

that have undergone damages under seismic loadings. The rules of design as set forth in the present

document are simplifications of more elaborate requirements.

Although the guidelines contained in this document were drawn to produce, when properly employed,

a reasonable assessment of the seismic vulnerability of an undamaged structure, a reasonable

assessment of a structure damaged by a seismic event and a structural rehabilitation of the assessed

concrete structure with an appropriate margin of safety, these guidelines are not a replacement of

sound and experienced engineering. In order to attain the intended results on assessment and

rehabilitation design, the document must be used as a whole, and alternative procedures should be

employed only when explicitly permitted by the guidelines. The minimum dimensioning guides as

prescribed in the document replace, in most cases, more elaborate procedures as those prescribed in

the national code or, if no national code exists, in internationally recognized full fledged codes, and the

eventual economic impact is compensated by the simplicity of the procedures prescribed here.

The professional applying the procedures set forth by these guidelines should meet the legal

requirements for structural designers in the country of adoption and have training and a minimum

appropriate knowledge of structural mechanics, statics, strength of materials, structural analysis, and

reinforced concrete design and construction.

While buildings rehabilitated in accordance with these guidelines are expected to perform within the

selected performance levels for the applicable design earthquakes, compliance with this guidelines are

necessary but may not guarantee the sought for performance, as current knowledge of structural

behavior under seismic loads, and of the loads themselves, is yet incomplete.
2 Normative references

The following referenced documents are indispensable for the application 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 679, Methods of testing cements - Determination of strength
ISO 680, Cement - Test methods - Chemical analysis
ISO 863, Cement - Test methods - Pozzolanicity test for pozzolanic cements
© ISO 2009 – All rights reserved 1
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oSIST ISO/DIS 28841:2010
ISO/DIS 28841
ISO 3010, Bases for design of structures - Seismic actions on structures
ISO 4354, Wind actions on structures
ISO 6274, Concrete - Sieve analysis of aggregates
ISO 6782, Aggregates for concrete - Determination of bulk density

ISO 6783, Coarse aggregates for concrete - Determination of particle density and water absorption -

Hydrostatic balance method
ISO 6934-1, Steel for the prestressing of concrete Part 1: General requirements

ISO 6934-3, Steel for the prestressing of concrete -- Part 3: Quenched and tempered wire

ISO 6934-4, Steel for the prestressing of concrete -- Part 4: Strand

ISO 6934-5, Steel for the prestressing of concrete -- Part 5: Hot-rolled steel bars with or without

subsequent processing
ISO 6935-1, Steel for the reinforcement of concrete - Part 1: Plain bars
ISO 6935-2, Steel for the reinforcement of concrete - Part 2: Ribbed bars

ISO 6935-3, Cor: 2000 Steel for the reinforcement of concrete - Part 3: Welded fabric

ISO 7033, Fine and coarse aggregates for concrete - Determination of the particle mass-per-volume

and water absorption - Pycnometer method

ISO 9194, Bases for design of structures - Actions due to the self-weight of structures, non-structural

elements and stored materials – Density
ISO 9597, Cements - Test methods - Determination of setting time and soundness

ISO 10144, Certification scheme for steel bars and wires for the reinforcement of concrete. Welded-

wire fabric

ISO 3766,2003 Construction drawings -- Simplified representation of concrete reinforcement.

3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
acceleration of gravity
the acceleration produced by gravity at the surface of earth
NOTE For the application of this guidelines its value can be app
...

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