TCVN 9386:2012 final EN

TCVN 9386:2012 is converted from TCXDVN 375:2006 into National Standard according to provisions at Clause 1, Article 69 of the Law on Standards and Technical Regulations and Point b, Clause 2, Article 7 of Decree No. 1272007NDCP of August 01, 2007, issued by Government, dated August 01, 2007, detailing the implementation of a number of articles of the Law on Standards and Technical Regulations. TCVN 9386:2012 is compiled by the Institute for Building Science and Technology Ministry of Construction, requested by Ministr of Construction, authenticated by the Directorate for Standards, Metrology and Quality, and announced by Ministry of Science and Technology.

PART 1: GENERAL RULES, SEISMIC ACTIONS AND

RULES FOR BUILDINGS PART 2: FOUNDATIONS, RETAINING STRUCTURES

AND GEOTECHNICAL ASPECTS

Hanoi - 2012

5.6 Provisions for anchorages and splices

5.7 Design and detailing of secondary seismic elements5.8 Concrete foundation elements

5.9 Local effects due to masonry or concrete infills

5.10 Provisions for concrete diaphragms

5.11 Precast concrete structures

6 Specific rules for steel buildings

6.6 Design and detailing rules for moment resisting frames

6.7 Design and detailing rules for frames with concentric bracings

6.8 Design and detailing rules for frames with eccentric bracings

6.9 Design rules for inverted pendulum structures

6.10 Design rules for steel structures with concrete cores or concrete walls and for moment resisting frames combined with concentric bracings or infills

6.11 Control of design and construction

7 Specific rules for composite steel–concrete buildings

7.6 Rules for members

7.7 Design and detailing rules for moment frames

7.8 Design and detailing rules for composite concentrically braced frames

7.9 Design and detailing rules for composite eccentrically braced frames

7.10 Design and detailing rules for structural systems made of reinforced concrete shear walls composite with structural steel elements

7.11 Design and detailing rules for composite steel plate shear walls

8 Specific rules for timber buildings

8.1 General

8.2 Materials and properties of dissipative zones

8.3 Ductility classes and behaviour factors

8.4 Structural analysis

8.5 Detailing rules

8.6 Safety verifications

8.7 Control of design and construction

9 Specific rules for masonry buildings

9.1 Scope

9.2 Materials and bonding patterns

9.3 Types of construction and behaviour factors

10.10 Safety verifications at Ultimate Limit State

Appendix A (informative): Elastic displacement response spectrum

Appendix B (informative): Determination of the target displacement for nonlinear static (pushover) analysis

Appendix C (normative): Design of the slab of steel-concrete composite beams at column joints in moment resisting frames

beam-Appendix D (Reference): Symbols

Appendix E (Regulation): Degree and importance factor

Appendix F: Grading and classification of construction works

Appendix G (Regulation): Ground acceleration zone map of Vietnam

Appendix H (Regulation): Table of ground acceleration of administrative locationsAppendix I (Reference): Table I.1 – Table of converting peak ground acceleration into earthquake level

Part 2: Foundations, retaining structures and geotechnical aspects

1 General

1.1 Field of application

1.2 Further reference documents for this regulation

1.3 Assumptions

1.4 Distinguish between principles and prescripts

1.5 Terms and definitions

3.2 Stiffness parameters and resistance parameters

4 Requirements in choosing building location and ground soil

4.1 Choosing building location

4.2 Surveillance and study about ground

5 Foundation system

5.1 General requirements

5.3 Designed effect

5.4 Criteria in testing and size determination

6 Interaction between earth and structure

7 Retaining wall structure

7.1 General requirements

7.2 Choice of structures and notes about designing

7.3 Analysis methods

7.4 Strength and stability test

Appendix A (reference): Relief amplification factor

Appendix B (compulsory): Experimental graphs used to analyzing simplified liquefaction

Appendix C (compulsory): Pile head’s static stiffness

Appendix D (reference): Structure-soil interaction (ssi): general effects and importanceAppendix E (compulsory): Simplified analyzing method for retaining wall structure Appendix F (reference): Earthquake load bearing capacity of shallow foundation

TCVN 9386:2012 is converted from TCXDVN 375:2006 into National Standardaccording to provisions at Clause 1, Article 69 of the Law on Standards and TechnicalRegulations and Point b, Clause 2, Article 7 of Decree No 127/2007/ND-CP of August

01, 2007, issued by Government, dated August 01, 2007, detailing the implementation of

a number of articles of the Law on Standards and Technical Regulations

TCVN 9386:2012 is compiled by the Institute for Building Science and Technology Ministry of Construction, requested by Ministr of Construction, authenticated by theDirectorate for Standards, Metrology and Quality, and announced by Ministry of Scienceand Technology

TCVN 9386:2012: Design of structures for earthquake resistances is compiled based onthe accepted Eurocode 8: Design of structures for earthquake resistance, with additions orsubstitutes to comply with typical characteristics of Vietnam

Eurocode 8 includes 6 parts:

EN1998 - 1: General provisions, seismic impacts and regulations for building structure;EN1998 - 2: Specific provisions relevant to bridges;

EN1998 - 3: Provisions for the seismic assessment and retrofitting of existing buildingsEN1998 - 4: Specific provisions relevant to silos, tanks and pipelines;

EN1998 - 5: Specific provisions relevant to foundations, retaining structures andgeotechnical aspects;

EN1998 - 6: Specific provisions relevant to towers, masts and chimneys

This new issued document mentions terms and provisions for buildings, with contentcorresponding to the following parts of Eurocode 8

Part 1 corresponds to EN1998 - 1;

Phần 2 corresponds to EN1998 - 5;

Additional or substitute parts for contents of Part 1

Appendix E: Degree and importance factor

Appendix F: Grading and classification of construction works

Appendix G: Ground acceleration zone map of Vietnam

Appendix H: Table of ground acceleration of administrative locations

Appendix I: Table of converting peak ground acceleration into earthquake level

The common reference standards cited in Article 1.2.1 has not been replaced by thecurrent standards of Vietnam, because of the need to ensure the standard uniformity withEuropean standards system Vietnam standard system approaches to European standardssystem to release the cited standard as follows

Ground acceleration zone map of Vietnam is the result of an independent project of Statelevel: "Research on earthquake forecasting and ground oscillations in Vietnam,implemented by the Institute of Geophysics, and accepted by the Scientific Council ofState level in 2005 The map used in this document has the reliability and legal valuewhich is equivalent to a specific version of a map with the same name which has beenrevised based on recommendations in an evaluation report of the State’s AcceptanceCouncil

In Vietnam’s ground acceleration zone map, reference peak ground acceleration agR is

expressed by isolines Value agR between two isolines is determined by the principle of

linear interpolation In regions of dispute ground acceleration, value agR is determined bythe Investor

Peak ground acceleration agR can be converted into earthquake level by MSK-64 scale,

MM scale or other scales when applying different seismic resistant design standards

According to the value of the design ground acceleration ag = I x agR , earthquakes areclassified into 3 types:

- Strong earthquake ag ≥ 0,08g, seismic resistance must be calculated;

- Weak earthquake 0,04g ≤ ag < 0,08g, mitigated seismic resistance methods are applied;

- Very weak earthquake ag < 0,04g, seismic resistance design is not required

In Eurocode 8, two types of spectral curves are recommended The spectral curve type 1

is used for region with seismic magnitude Ms ≥ 5,5 ; the spectral curve type 2 is used for

region with seismic magnitude Ms < 5,5 In this document, the spectral curve type 1 isused because most of regions of earthquake occurance in Vietnam have seismic

magnitude Ms ≥ 5,5

For different construction works, different seismic resistance are designed Depending onthe importance of the construction work, appropriate importance factor I shall beselected In case of having dispute over importance factor, value I shall be determined bythe Investor

DESIGN OF STRUCTURES FOR EARTHQUAKE RESISTANCES

PART 1: GENERAL RULES, SEISMIC ACTIONS AND RULES FOR

BUILDINGS

1 GENERAL

1.1 Scope

1.1.1 Applicable scope of the document: Design of structures for earthquake resistances

(1)P This document applies to the design and construction of buildings and civilengineering works in seismic regions Its purpose is to ensure that in the event ofearthquakes:

- Human lives are protected;

- Damage is limited; and

- Structures important for civil protection remain operational

NOTE: The random nature of the seismic events and the limited resources available tocounter their effects are such as to make the attainment of these goals only partiallypossible and only measurable in probabilistic terms The extent of the protection that can

be provided to different categories of buildings, which is only measurable in probabilisticterms, is a matter of optimal allocation of resources and is therefore expected to varyfrom country to country, depending on the relative importance of the seismic risk withrespect to risks of other origin and on the global economic resources

(2)P Special structures, such as nuclear power plants, offshore structures and large dams,are beyond the scope of this document

(3)P This document contains only those provisions that, in addition to the provisions ofthe other relevant standard documents, must be observed for the design of structures inseismic regions It complements in thisrespect the other standard documents

1.1.2 Scope of Part 1

(1) This document applies to the design of buildings and civil engineering works inseismic regions It is subdivided in 10 Sections, some of which are specifically devoted tothe design of buildings

(2) Section 2 contains the basic performance requirements and compliance criteriaapplicable to buildings and civil engineering works in seismic regions

(3) Section 3 gives the rules for the representation of seismic actions and for theircombination with other actions

(4) Section 4 contains general design rules relevant specifically to buildings

(5) Sections 5 to 9 contain specific rules for various structural materials and elements,relevant specifically to buildings as follows:

- Section 5: Specific rules for concrete buildings;

- Section 6: Specific rules for steel buildings;

- Section 7: Specific rules for composite steel-concrete buildings;

- Section 8: Specific rules for timber buildings;

- Section 9: Specific rules for masonry buildings

(6) Section 10 contains the fundamental requirements and other relevant aspects of designand safety related to base isolation of structures and specifically to base isolation ofbuildings

(7) Appendix C contains additional elements related to the design of slab reinforcement

in steel-concrete composite beams at beam-column joints of moment frames

NOTE: Informative Appendix A and informative Appendix B contain additionalelements related to the elastic displacement response spectrum and to target displacementfor pushover analysis

1.2 Cited documents

(1)P This Standard incorporates by dated or undated reference, provisions from otherpublications These normative references are cited at the appropriate places in the textand the publications are listed hereafter For dated references, subsequent amendments to

or revisions of any of these publications apply to this Standard only when incorporated in

it by amendment or revision For undated references the latest edition of the publicationreferred to applies

1.2.1 General reference standards

EN 1990, Eurocode - Basis of structural design.

EN 1992-1-1, Eurocode 2 - Design of concrete structures - Part 1-1: General - Common rules for building and civil engineering structures.

EN 1993-1-1, Eurocode 3 - Design of steel structures - Part 1-1: General-rules.

EN 1994-1-1, Eurocode 4 - Design of composite steel and concrete structures - Part 1-1: General - Common rules and rules for buildings.

EN 1995-1-1, Eurocode 5 - Design of timber structures - Part 1-1: General - Common rules and rules for buildings.

EN 1996-1-1, Eurocode 6 - Design of masonry structures - Part 1-1: General - rules reinforced and unreinforced masonry.

EN 1997-1-1, Eurocode 7 - Geotechnical design - Part 1-1 General – rules.

1.2.2 Other reference Codes and Standards

(1)P For the application of this Standard, reference shall be made to EN 1990, to EN

1997 and to EN 1999

(2) This Standard incorporates other normative references cited at the appropriate places

in the text They are listed below:

TCVN 7870 (ISO 80000), The international system of units (SI) and its application

EN 1090-1, Execution of steel structures - Part 1: General rules and rules for buildings

1.3 Assumptions

(1) General assumptions

- The choice of the structural system and the design of the structure is made byappropriately qualified and experienced personnel;

- Execution is carried out by personnel having the appropriate skill and experience;

- Adequate supervision and quality control is provided during execution of the work,i.e.in design offices, factories, plants, and on site;

- The construction materials and products are used as specified in current standarddocument, or in the relevant execution standards, or reference material of productspecifications;

- The structure will be adequately maintained;

- The structure will be used in accordance with the design assumptions

(2)P It is assumed that no change in the structure will take place during the constructionphase or during the subsequent life of the structure, unless proper justification andverification is provided Due to the specific nature of the seismic response this applieseven in the case of changes that lead to an increase of the structural resistance

1.4 Distinction between Principles and Application Rules

(1) The Principles comprise:

- General statements and definitions for which there is no alternative;

- Requirements and analytical models for which no alternative is permitted unlessspecifically stated

(2) The Principles are identified by the letter P following the paragraph number eg (1)P.(3) The Application Rules are generally recognised rules which comply with thePrinciples and satisfy their requirements

(4) It is permissible to use alternative design rules different from the Application Rules,provided that it is shown that the alternative rules accord with the relevant Principles andare at least equivalent with regard to the structural safety, serviceability and durability.(5) The Application Rules are identified by a number in brackets e.g (1)

1.5 Terms and definitions

1.5.1 Common terms

1.5.1.1 Construction work

The products are made up of human labor, construction materials and installationequipments They are linked to the land, may include parts under or above the ground,below or above the water surface, and built in accordance with the the design

The construction works include public buildings, houses, industrial buildings,transportation, irrigation, energy works and other works

Everything that is constructed or results from construction operations

NOTE: This definition accords with ISO 6707-1 The term covers both building and civilengineering works.

It refers to the complete construction works comprising structural, non-structural andgeotechnical elements

1.5.1.2 Type of building or civil engineering works

Type of construction works designating its intended purpose, e.g dwelling house,retaining wall, industrial building, road bridge

1.5.1.3 Type of construction

indication of the principal structural material, e.g.reinforced concrete construction, steelconstruction, timber construction, masonry construction, steel and concrete compositeconstruction

1.5.1.12.3 Transient design situation

Design situation that is relevant during a period much shorter than the design working life

of the structure and which has a high probability of occurrence

NOTE: A transient design situation refers to temporary conditions of the structure, of use,

or exposure, e.g during construction or repair

1.5.1.12.4 Persistent design situation

Design situation that is relevant during a period of the same order as the design workinglife of the structure

NOTE: Generally it refers to conditions of normal use

1.5.1.12.5 Accidental design situation

Design situation involving exceptional conditions of the structure or its exposure,including fire, explosion, impact or local failure

1.5.1.12.6 Fire design

Design of a structure to fulfil the required performance in case of fire

1.5.1.12.7 Seismic design situation

Design situation involving exceptional conditions of the structure when subjected to aseismic event

1.5.1.12.8 Design working life

Assumed period for which a structure or part of it is to be used for its intended purposewith anticipated maintenance but without major repair being necessary

1.5.1.12.12 Limit states

States beyond which the structure no longer fulfils the relevant design criteria.

1.5.1.12.13 Ultimate limit states

States associated with collapse or with other similar forms of structural failure

NOTE: They generally correspond to the maximum load-carrying resistance of astructure or structural member

1.5.1.12.14 Serviceability limit states

States that correspond to conditions beyond which specified service requirements for astructure or structural member are no longer met

1.5.1.12.15 Irreversible serviceability limit states

Serviceability limit states where some consequences of actions exceeding the specifiedservice requirements will remain when the actions are removed

1.5.1.12.16 Reversible serviceability limit states

Serviceability limit states where no consequences of actions exceeding the specifiedservice requirements will remain when the actions are removed

NOTE: Reliability covers safety, serviceability and durability of a structure

1.5.1.12.21 Reliability differentiation

Measures intended for the socio-economic optimisation of the resources to be used tobuild construction works, taking into account all the expected consequences of failuresand the cost of the construction works

1.5.1.12.22 Basic variable

Part of a specified set of variables representing physical quantities which characterizeactions and environmental influences, geometrical quantities, and material propertiesincluding soil properties

a) Set of forces (loads) applied to the structure (direct action).

b) Set of imposed deformations or accelerations caused, for example: by temperaturechanges, moisture variation, uneven settlement or earthquakes (indirect action)

1.5.1.13.2 Effect of action (E)

Effect of actions (or action effect) on structural members, (e.g.internal force, moment,stress, strain) or on the whole structure (e.g.deflection, rotation)

1.5.1.13.3 Permanent action (G)

Action that is likely to act throughout a given reference period and for which thevariation in magnitude with time is negligible, or for which the variation is always in thesame direction (monotonic) until the action attains a certain limit value

1.5.1.13.4 Variable action (Q)

Action for which the variation in magnitude with time is neither negligible normonotonic

1.5.1.13.5 Accidental action (A)

Action, usually of short duration but of significant magnitude, that is unlikely to occur on

a given structure during the design working life

NOTE 1: An accidental action can be expected in many cases to cause severeconsequences unless appropriate measures are taken

NOTE 2: Impact, snow, wind and seismic actions may be variable or accidental actions,depending on the available information on statistical distributions

1.5.1.13.6 Seismic action (AE )

Action that arises due to earthquake ground motions

1.5.1.13.7 Geotechnical action

Action transmitted to the structure by the ground, fill or groundwater

1.5.1.13.8 Fixed action

Action that has a fixed distribution and position over the structure or structural membersuch that the magnitude and direction of the action are determined unambiguously for thewhole structure or structural member if this magnitude and direction are determined atone point on the structure or structural member

Dynamic action represented by an equivalent static action in a static model

1.5.1.13.14 Characteristic value of an action (FK )

Principal representative value of an action

NOTE: In so far as a characteristic value can be fixed on statistical bases, it is chosen so

as to correspond to a prescribed probability of not being exceeded on the unfavourableside during a "reference period" taking into account the design working life of thestructure and the duration of the design situation

1.5.1.13.15 Reference period

Chosen period of time that is used as a basis for assessing statistically variable actions,and possibly for accidental actions

1.5.1.13.16 Combination value of a variable action ( 0 Q K )

Value chosen - in so far as it can be fixed on statistical bases - so that the probability thatthe effects caused by the combination will be exceeded is approximately the same as bythe characteristic value of an individual action It may be expressed as a determined part

of the characteristic value by using a factor 0≤1

1.5.1.13.17 Frequent value of a variable action ( 1 Q K )

Value determined - in so far as it can be fixed on statistical bases - so that either the totaltime, within the reference period, during which it is exceeded is only a small given part ofthe reference period, or the frequency of it being exceeded is limited to a given value Itmay be expressed as a determined part of the characteristic value by using a factor 1≤1

1.5.1.13.18 Quasi-permanent value of a variable action ( 2 Q K )

Value determined so that the total period of time for which it will be exceeded is a largefraction of the reference period It may be expressed as a determined part of the

characteristic value by using a factor 2≤1

1.5.1.13.19 Accompanying value of a variable action (Q K )

Value of a variable action that accompanies the leading action in a combination

NOTE: The accompanying value of a variable action may be the combination value, thefrequent value or the quasi-permanent value

1.5.1.13.20 Representative value of an action (Frep )

Value used for the verification of a limit state A representative value may be the

characteristic value (Fk) or an accompanying value (FK)

1.5.1.13.21 Design value of an action (Fd )

value obtained by multiplying the representative value by the partial factor f

NOTE The product of the representative value multiplied by the partial factor F = sd x

f may also be designated as the design value of the action (See 6.3.2)

1.5.1.14.2 Design value of a material or product property (Xd or Rd )

Value obtained by dividing the characteristic value by a partial factor m or M or, in

special circumstances, by direct determination.

1.5.1.14.3 Nominal value of a material or product property (Xnom or Rnom )

Value normally used as a characteristic value and established from an appropriatedocument

1.5.1.15 Terms relating to geometrical data

1.5.1.15.1 Characteristic value of a geometrical property (ak )

Value usually corresponding to the dimensions specified in the design Where relevant,values of geometrical quantities may correspond to some prescribed fractiles of thestatistical distribution

1.5.1.15.2 Design value of a geometrical property (ad )

Generally a nominal value Where relevant, values of geometrical quantities maycorrespond to some prescribed fractile of the statistical distribution.

NOTE: The design value of a geometrical property is generally equal to the characteristicvalue However, it may be treated differently in cases where the limit state underconsideration is very sensitive to the value of the geometrical property, for example whenconsidering the effect of geometrical imperfections on buckling In such cases, the designvalue will normally be established as a value specified directly, for example in anappropriate European Standard or Prestandard Alternatively, it can be established from astatistical basis, with a value corresponding to a more appropriate fractile (e.g.a rarervalue) than applies to the characteristic value

1.5.1.16 Terms relating to structural analysis

1.5.1.16.1 Structural analysis

Procedure or algorithm for determination of action effects in every point of a structure.NOTE: A structural analysis may have to be performed at three levels using differentmodels: global analysis, member analysis, local analysis

1.5.1.16.2 Global analysis

Determination, in a structure, of a consistent set of either internal forces and moments, orstresses, that are in equilibrium with a particular defined set of actions on the structure,and depend on geometrical, structural and material properties

1.5.1.16.3 First order linear-elastic analysis without redistribution

Elastic structural analys is based on linear stress/strain or moment/curvature laws andperformed on the initial geometry

1.5.1.16.4 First order linear-elastic analysis with redistribution

Linear elastic analysis in which the internal moments and forces are modified forstructural design, consistently with the given external actions and without more explicitcalculation of the rotation capacity

1.5.1.16.5 Second order linear-elastic analysis

Elastic structural analysis, using linear stress/strain laws, applied to the geometry of thedeformed structure

1.5.1.16.6 First order non-linear analysis

Structural analysis, performed on the initial geometry, that takes account of the non-lineardeformation properties of materials

NOTE: First order non-linear analysis is either elastic with appropriate assumptions, orelastic-perfectly plastic, or elasto-plastic or rigid-plastic

1.5.1.16.7 Second order non-linear analysis

Structural analysis, performed on the geometry of the deformed structure, that takesaccount of the non-linear deformation properties of materials

NOTE: Second order non-linear analysis is either elastic-perfectly plastic or plastic.

elasto-1.5.1.16.8 First order elastic-perfertly plastic analysis

Structural analysis based on moment/curvature relationships consisting of a linear elasticpart followed by a plastic part without hardening, performed on the initial geometry ofthe structure

1.5.1.16.9 Second order elastic-perfertly plastic analysis

Structural analysis based on moment/curvature relationships consisting of a linear elasticpart followed by a plastic part without hardening, performed on the geometry of thedisplaced (or deformed) structure

1.5.1.16.10 Elasto-plastic analysis (first or second order)

Structural analysis that uses stress-strain or moment/curvature relationships consisting of

a linear elastic part followed by a plastic part with or without hardening

NOTE: In general, it is performed on the initial structural geometry, but it may also beapplied to the geometry of the displaced (or deformed) structure

1.5.1.16.11 Rigid plastic analysis

Analysis, performed on the initial geometry of the structure, that uses limit analysistheorems for direct assessment of the ultimate loading

NOTE: The moment/curvature law is assumed without elastic deformation and withouthardening

1.5.2 Further terms used in the Standard

1.5.2.1 Behaviour factor

Factor used for design purposes to reduce the forces obtained from a linear analysis, inorder to account for the non-linear response of a structure, associated with the material,the structural system and the design procedures

1.5.2.2 Capacity design method

Design method in which elements of the structural system are chosen and suitablydesigned and detailed for energy dissipation under severe deformations while all otherstructural elements are provided with sufficient strength so that the chosen means ofenergy dissipation can be maintained

1.5.2.5 Dynamically independent unit

Structure or part of a structure which is directly subjected to the ground motion andwhose response is not affected by the response of adjacent units or structures

1.5.2.9 Primary seismic members

Members considered as part of the structural system that resists the seismic action,modelled in the analysis for the seismic design situation and fully designed and detailedfor earthquake resistance in accordance with the rules of this Standard

1.5.2.10 Secondary seismic members

Members which are not considered as part of the seismic action resisting system andwhose strength and stiffness against seismic actions is neglected

NOTE 2: They are not required to comply with all the rules of this Standard, but aredesigned and detailed to maintain support of gravity loads when subjected to thedisplacements caused by the seismic design situation

1.5.2.11 Rigid basement

The part of a building or a construction work is considered to be absolutely regidcomparing to its upper part, for example, for the antenna on the roof, the part from theroof down is considered as the regid basement of the antenna

1.5.2.12 Second order effects (P- effects)

A structural calculation measure based on the deformation diagram

1.6 Symbols

1.6.1 General

(1) The symbols indicated in Appendix D For the material-dependent symbols, as well asfor symbols not specifically related to earthquakes, the provisions of other relevantstandard documents apply

(2) Further symbols, used in connection with seismic actions, are defined in the textwhere they occur, for ease of use However,in addition, the most frequently occurringsymbols used in this Standard are listed and defined in 1.6.2 and 1.6.3

1.6.2 Further symbols used in Sections 2 and 3

AEd Design value of seismic action (= I x AEk).

AEk Characteristic value of the seismic action for the reference return period

Ed Design value of action effects

NSPT Standard Penetration Test blow-count (SPT)

PNCR Reference probability of exceedance in 50 years of the reference seismic

action for the no-collapse requirement

Se(T) Elastic horizontal ground acceleration response spectrum also called "elastic

response spectrum” At T=0, the spectral acceleration given by this spectrum equals the design ground acceleration on type A ground multiplied by the soil factor S

Sve(T) Elastic vertical ground acceleration response spectrum

SDe(T) Elastic displacement response spectrum

Sd(T) Design spectrum (for elastic analysis) At T=0, the spectral acceleration

given by this spectrum equals the design ground acceleration on type A ground multiplied by the soil factor S

T Vibration period of a linear single degree of freedom system

Ts Duration of the seismic motion in which the amplitude is not less than 1/3 of

the maximum amplitude

TNCR Reference return period of the reference seismic action for the no-collapse

requirement

agR Reference peak ground acceleration on type A ground

ag Design ground acceleration on type A ground

avg Design ground acceleration in the vertical direction

cu Undrained shear strength of soil

dg Design ground displacement

g Acceleration of gravity

q Behaviour factor

vs,30 Average value of propagation velocity of Swaves in the upper 30 m of the

soil profile at shear strain of 10-5or less

I Importance factor

 Damping correction factor

 Viscous damping ratio (in percent)

2,i Combination coefficient for the quasi-permanent value of a variable action i.

E,i Combination coefficient for a variable action i, to be used when determining

the effects of the design seismic action

1.6.3 Further symbols used in Section 4

EE Effect of the seismic action

EEdx, EEdy Design values of the action effects due to the horizontal components (x

and y) of the seismic action

EEdz Design value of the action effects due tothe vertical component of the

seismic action

 Ratio of the design ground acceleration to the acceleration of gravity

F i horizontal seismic force at storey i.

F a Horizontal seismic force acting on a non-structural element (appendage)

F b Base shear force

H Building height from the foundation or from the top of a rigid basement

Lmax, Lmin Larger and smaller in plan dimension of the building measured in orthogonal

directions

Rd Design value of resistance

Sa Seismic coefficient for non-structural elements

T1 Fundamental period of vibration of a building

Ta Fundamental period of vibration ofa non-structural element

Wa Weight of a non-structural element

dr Design interstorey drift

ea Accidental eccentricity of the mass of one storey from its nominal location

h Interstorey height

mi Mass of storey i.

n Number of storeys above the foundation or the top of a rigid basement

qa Behaviour factor of a non-structural element

qd Displacement behaviour factor

Si Displacement of mass mi in the fundamental mode shape of a building.

Zi Height of mass mi above the level of application of the seismic action.

a Importance factor of a non-structural element

d Overstrength factor for diaphragms

 Interstorey drift sensitivity coefficient

1.6.4 Further symbols used in Section 5

Ac Area of section of concrete member

Ash Total area of horizontal hoops in a beam-column joint

Asi Total area of steel bars in each diagonal direction of a coupling beam

Ast Area of one leg of the transverse reinforcement

Asv Total area of the vertical reinforcement in the web of the wall

Asv,i Total area of column vertical bars between corner bars in one direction

through a joint

Aw Total horizontal cross-sectional area of a wall

Asi Sum of areas of all inclined bars in both directions, in wall reinforced with

inclined bars against sliding shear

Asj Sum of areas of vertical bars of web in a wall, or ofadditional barsarranged in

the wall boundary elements specifically for resistance against sliding shear

MRb Sum of design values of moments of resistance of the beams framing into a

joint in the direction of interest

MRc Sum of design values of the moments of resistance of the columns framing

into a joint in the direction of interest

Do Diameter of confined core in a circular column

Mi,d End moment of a beam or column for the calculation of its capacity design

shear

MRb,i Design value of beam moment of resistance at end i

MRc,i Design value of column moment of resistance at end i

NEd Axial force from the analysis for the seismic design situation

T1 Fundamental period of the building in the horizontal direction of interest

TC Corner period at the upper limit of the constant acceleration region of the

elastic

Spectrum

V'Ed Shear force in a wall from the analysis for the seismic design situation

Vdd Dowel resistance of vertical bars in a wall

VEd Design shear force in a wall

VEd,max Maximum acting shear force at end section of a beam from capacity design

Vid Contribution of inclined bars to resistance of a wall against sliding shear

VRd, c Design value of shear resistance for members withoutshear reinforcement in

accordance with EN1992-1-1:2004

VRd, S Design value of shear resistance against sliding

b Width of bottom flange of beam

bc Cross-sectional dimension of column

beff Effective flange width of beam in tension at the face of a supporting column

bi Distance between consecutive bars engaged by a corner of a tie or by a

cross-tie in a column

b0 Width of confined core in a column or in the boundary element of a wall (to

centreline of hoops)

bW Thickness of confined parts of a wall section, or width of the web of a beam

bw0 Thickness of web of a wall

d Effective depth of section

dbL Longitudinal bar diameter

dbW Diameter of hoop

fcd Design value of concrete compressive strength

fctm Mean value of tensile strength of concrete

fyd Design value of yield strength of steel

fyd, h Design value of yield strength of the horizontal web reinforcement

fyd, v Design value of yield strength ofthe vertical web reinforcement

fyld Design value of yield strength ofthe longitudinal reinforcement

fywd Design value of yield strength of transverse reinforcement

hjw Distance between beam top and bottom reinforcement

h0 Depth of confined core in a column (to centreline of hoops)

hs Clear storey height

hw Height of wall or cross-sectional depth of beam

kD Factor reflecting the ductility class in the calculation of the required column

depth for anchorage of beam bars in a joint, equal to 1 for DCH and to 2/3

for DCM

kw Factor reflecting the prevailing failure mode in structural systems with walls

lc1 Clear length of a beam or a column

lcr Length of critical region

li Distance between centrelines of the two sets of inclinedbars at the base

section of walls with inclined bars against sliding shear

lw Length of cross-section of wall

n Total number of longitudinal bars laterally engaged by hoops or cross ties on

perimeter of column section

q0 Basic value of the behaviour factor

S Spacing of transverse reinforcement

Xu Neutral axis depth

Z Internal lever arm

 Confinement effectiveness factor, angle between diagonal bars and axis of a

coupling beam

0 Prevailing aspect ratio of walls of the structural system

1 Multiplier of horizontal design seismic action at formation of first plastic

hinge in the system

u Multiplier of horizontal seismic design action at formation of global plastic

mechanism

c Partial factor for concrete

Rd Model uncertainty factor on design value of resistances in the estimation of

capacity design action effects, accounting for various sources of overstrength

s Partial factor for steel

cu2 Ultimate strain of unconfined concrete

cu2,c Ultimate strain of confined concrete

su,k Characteristic value of ultimate elongation of reinforcing steel

sy,d Design value of steel strain at yield

 Reduction factor on concrete compressive strength due to tensile strains in

transverse direction

 Ratio, VEd,min/VEd,max, between the minimum and maximum acting shear

forces at the end section of a beam

f Concrete-to-concrete friction coefficient under cyclic actions

 Curvature ductility factor

 Displacement ductility factor

V Axial force due in the seismic design situation

 Normalised neutral axis depth

 Tension reinforcement ratio

' Compression steel ratio in beams

cm Mean value of concrete normal stress

h Reinforcement ratio of horizontal web bars in a wall

1 Total longitudinal reinforcement ratio

max Maximum allowed tension steel ratio in the critical region of primary seismic

beams

v Reinforcement ratio of vertical web bars in a wall

w Shear reinforcement ratio

v Mechanical ratio of vertical web reinforcement

wd Mechanical volumetric ratio of confining reinforcement

1.6.5 Further symbols used in Section 6

MEd design bending moment from the analysisfor the seismic design situation

Mp1,RdA design value of plastic moment resistance at end A of a member

Mp1,RdB design value of plastic moment resistance at end B of a member

NEd design axial force from the analysisfor the seismic design situation

NEd,E axial force from the analysis due to the design seismic action alone

NEd,G axial force due to the non-seismic actions included in the combination of

actions for the seismic design situation

Np1,Rd design value of yield resistance in tension of the gross cross-section of a

member in accordance with EN 1993-1-1:2004

NRd

(MEd, VEd) design value of axial resistance of column or diagonal in accordance with EN1993-1-1:2004, taking into account the interaction with the bending moment

MEd and the shear VEd in the seismic situation

Rd resistance of connection in accordance with EN 1993-1-1:2004

Rfy plastic resistance of connected dissipative member based on the design yield

stress of material as defined in EN 1993-1-1:2004

VEd design shear force from the analysisfor the seismic design situation

VEd,G shear force due to the non seismic actions included in the combination of

actions for the seismic design situation

VEd,M shear force due to the application of the plastic moments of resistance at the

two ends of a beam

Vwp,Ed design shear force in web panel due to the design seismic action effects

Vwp,Rd design shear resistance of the web panel in accordance with EN

1993-1-1:2004

e length of seismic link

fy nominal yield strength of steel

fymax maximum permissible yield stress of steel

tw web thickness of a seismic link

tf flange thickness of a seismic link

 multiplicative factor on axial force NEd,E from the analysis due to the design

seismic action, for the design of the non-dissipative members in concentric

or eccentric braced frames per Clause (l) of 6.7.4 and 6.8.3 respectively

 ratio of the smaller design bending moment MEd,A at one end of a seismic link

to the greater bending moments MEd,B at the end where plastic hinge forms, both moments taken in absolute value

1 multiplier of horizontal design seismic action at formation of first plastic

hinge in the system

u multiplier of horizontal seismic design action at formation of global plastic

mechanism

M partial factor for material property

ov material overstrength factor

 beam deflection at midspan relative to tangent to beam axis at beam end (see

Figure 30)

pb multiplicative factor on design value Npl,Rd of yield resistance in tension of

compression brace in a V bracing, for the estimation of the unbalanced seismic action effect on the beam to which the bracing is connected

s partial factor for steel

p rotation capacity of the plastic hinge region

 non-dimensional slenderness of a member as defined in EN 1993-1-1:2004

1.6.6 Further symbols used in Section 7

Apl Horizontal area of the plate

Ea Modulus of Elasticity of steel

Ecm Mean value of Modulus of Elasticityof concrete inaccordance with EN

1992-1-1:2004

la Second moment of area of the steel section part of a composite section, with

respect to the centroid ofthe composite section

lc Second moment of area of the concrete part of a composite section, with

respect to the centroid of the composite section

leq Equivalent second moment of area of the composite section

ls Second moment of area of the rebars in a composite section, with respect to

the centroid of the composite section

Mp1,Rd,c Design value of plastic moment resistance of column, taken as lower bound

and computed taking into account the concrete component of the section and only the steel components of the section classified as ductile

MU,Rd,b Upper bound plastic resistance of beam, computed taking into account the

concrete component of the section and all the steel components in the

section, including those not classified as ductile

Vwp,Ed Design shear force in web panel, computed on the basis of the plastic

resistance of the adjacent dissipative zones in beams or connections

Vwp,Rd Design shear resistance of the compositesteel-concrete web panel in

accordance with EN 1994-1-1:2004

b Width of the flange

be Partial effective width of flangeon each side of the steel web

beff Total effective width of concrete flange

b0 Width (minimum dimension) of confinedconcrete core (to centreline of

hoops)

dbL Diameter of longitudinal rebars

dbw Diameter of hoops

fyd Design yield strength of steel

fydf Design yield strength ofsteel in the flange

fydw Design strength of web reinforcement

hb Depth of composite beam

bb Width of composite beam

hc Depth of composite column section

kr Rib shape efficiency factor of profiled steel sheeting

kt Reduction factor of design shear resistance of connectors in accordance with

EN 1994-1-1:2004

lcl Clear length of column

lcr Length of critical region

n Steel-to-concrete modular ratio for short term actions

r Reduction factor on concrete rigidity for the calculation of the stiffness of

composite columns

tf Thickness of flange

c Partial factor for concrete

M Partial factor for material property

ov Material overstrength factor

s Partial factor for steel

a Total strain of steel at Ultimate Limit State

cu2 Ultimate compressive strain of unconfined concrete

 Minimum degree of connection as defined in 6.6.1.2of EN 1994-1-1:2004

1.6.7 Further symbols used in Section 8

E0 Modulus of Elasticity of timber for instantaneous loading

b Width of timber section

d Fastener’s diameter

h Depth of timber beams

kmod Modification factor for instantaneousloading on strength of timber in

accordance with EN 1995-1-1:2004

M Partial factor for material properties

1.6.8 Further symbols used in Section 9

ag,urm Upper value of the design ground acceleration at the site for use of

unreinforced masonry satisfying the provisions of this Standard

Amin Total cross-section area of masonry walls required in each horizontal

direction for the rules for “simple masonry buildings” to apply

fb, min Normalised compressive strength of masonry normal to the bed face

fbh, min Normalised compressive strength of masonry parallel to the bed face in the

plane of the wall

fm, min Minimum strength for mortar

h Greater clear height of the openings adjacent to the wall

hef Effective height of the wall

l Length of the wall

n Number of storeys above ground

pA,min Minimum sum of horizontal cross-sectional areas of shear walls in each

direction, as percentage of the total floor area per storey

pmax Percentage of the total floor area above the level

tef Effective thickness of the wall

A,max Maximum difference in horizontal shearwall cross-sectional area between

adjacent storeys of “simple masonry buildings”

m,max Maximum difference in mass between adjacent storeys of “simple masonry

buildings”

M Partial factors for masonry properties

s Partial factor for reinforcing steel

min Ratio between the length of the small and the length of the long side in plan

1.6.9 Further symbols used in Section 10

Keff Effective stiffness of the isolation system in the principal horizontal direction

Under consideration, at a displacement equal to the design displacement ddc

KV Total stiffness of the isolation system in the vertical direction

Kxi Effective stiffness of a given unit iin the x direction

Kyi Effective stiffness of a given unit i in the y direction

Teff Effective fundamental period of the superstructure corresponding to

horizontal translation, the superstructure assumed as a rigid body

Tf Fundamental period of the superstructure assumed fixed at the base

TV Fundamental period of the superstructure in the vertical direction, the

superstructure assumed as a rigid body

M Mass of the superstructure

ddc Design displacement of the effective stiffness centre in the direction

considered

ddb Total design displacement of an isolator unit

etot,y Total eccentricity in the y direction

fj Horizontal forces at each level j

ry Torsional radius of the isolation system

(xi, yi) Co-ordinates of the isolator unit i relative to the effective stiffness centre

(2) For calculations, the following units are recommended:

- Forces and loads:

- Unit mass:

- Mass:

- Unit weight:

- Stresses and strengths:

- Moments (bending, etc):

- Acceleration:

kN, kN/m, kN/m2

kg/m3, t/m3

kg, tkN/m3

N/mm2(= MN/m2 hoặc MPa), kN/m2 (=kPa)kNm

NOTE 1: The values to be ascribed to PNCR or to TNCR for use in Vietnam are PNCR = 10%and TNCR = 475 years

NOTE 2: The value of the probability of exceedance, PR, in TL years of a specific level ofthe seismic action is related to the mean return period, TR, of this level of the seismicaction in accordance with the expression TR = - TL/ In(1 - PR) So for a given TL, theseismic action may equivalently be specified either via its mean return period, TR, or itsprobability of exceedance, PR in TL years

- Damage limitation requirement

The structure shall be designed and constructed to withstand a seismic action having alarger probability of occurrence than the design seismic action, without the occurrence ofdamage and the associated limitations of use, the costs of which would bedisproportionately high in comparison with the costs of the structure itself The seismicaction to be taken into account for the “damage limitation requirement” has a probability

of exceedance, PDLR, in 10 years and a return period, TDLR In the absence of more preciseinformation, the reduction factor applied on the design seismic action in accordance with4.4.3.2(2) may be used to obtain the seismic action for the verification of the “damagelimitation requirement.”

NOTE 3: The values to be ascribed to PDLR or to TDLR for use in Vietnam are PDLR = 10%and TDLR = 95 years

(2)P Target reliabilities for the “no-collapse requirement” and for the “damage limitationrequirement” are established by the National Authorities for different types of buildings

or civil engineering works on the basis of the consequences of failure

(3)P Reliability differentiation is implemented by classifying structures into differentimportance classes An importance factor γI is assigned to each importance class.Wherever feasible this factor should be derived so as to correspond to a higher or lowervalue of the return period of the seismic event (with regard to the reference return period)

as appropriate for the design of the specific category of structures (see 3.2.1(3)).Definitions of degree and importance factor are given in Appendix E, Part 1

(4) The different levels of reliability are obtained by multiplying the reference seismicaction or, when using linear analysis, the corresponding action effects by this importancefactor Detailed guidance on the importance classes and the corresponding importancefactors is given in 4.2.5

NOTE At most sites the annual rate of exceedance, H(agR), of the reference peak groundacceleration agRmay be taken to vary with agR as: H(agR)  k0 agR-k, with the value of theexponent kdepending on seismicity, but being generally of the order of 3 Then, if theseismic action is defined in terms of the reference peak ground acceleration agR, the value

of the importance factor γI multiplying the reference seismic action to achieve the sameprobability of exceedance in TLyears as in the TLR years for which the reference seismicaction is defined, may be computed as γI  (TLR/ TL)-1/k Alternatively, the value of theimportance factor γI that needs to multiply the reference seismic action to achieve a value

of the probability of exceeding the seismic action, PL, in TL years other than the referenceprobability of exceedance PLR, over the same TL years, may be estimated as l  (PL/ PLR)- 1/k

2.2 Compliance Criteria

2.2.1 General

(1)P In order to satisfy the fundamental requirements in 2.1the following limit states shall

be checked (see 2.2.2and 2.2.3):

- Ultimate limit states;

- Damage limitation states

Ultimate limit states are those associated with collapse or with other forms of structuralfailure which might endanger the safety of people

Damage limitation states are those associated with damage beyond which specifiedservice requirements are no longer met

(2)P In order to limit the uncertainties and to promote a good behaviour of structuresunder seismic actions more severe than the design seismic action, a number of pertinentspecific measures shall also be taken (see 2.2.4)

(3) For well defined categories of structures in cases of low seismicity (see 3.2.1(4)), thefundamental requirements may be satisfied through the application of rules simpler thanthose given in the relevant Parts of this Standard

(4) In cases of very low seismicity, the provisions of this Standard need not be observed(see 3.2.1(5) and the notes therein for the definition of cases of very low seismicity).(5) Specific rules for ''simple masonry buildings” are given in Section 9 By conforming

to these rules, such “simple masonry buildings” are deemed to satisfy the fundamentalrequirements of this Standard without analytical safety verifications

2.2.2 Ultimate limit state

(1)P It shall be verified that the structural system has the resistance and energydissipation capacity specified in the relevant Parts of this Standard

(2) The resistance and energy-dissipation capacity to be assigned to the structure arerelated to the extent to which its non-linear response is to be exploited In operationalterms such balance between resistance and energy-dissipation capacityis characterised bythe values of the behaviour factor q and the associated ductility classification, which aregiven in the relevant Parts of this Standard As a limiting case, for the design of structuresclassified as low-dissipative, no account is taken of any hysteretic energy dissipation andthe behaviour factor may not betaken, in general, as being greater than the value of 1.5considered to account for overstrengths For steel or composite steel concrete buildings,

this limiting value of the q factor may be taken as being between 1.5 and 2 (see Note 1 of

Table 6.1 or Note 1 of Table 7.1, respectively) For dissipative structures the behaviourfactor is taken as being greater than these limiting values accounting for the hystereticenergy dissipation that mainly occurs in specifically designed zones, called dissipativezones or critical regions

NOTE: The value of the behaviour factor q should be limited by the limit state of

dynamic stability of the structure and by the damage due to low-cycle fatigue ofstructural details (especially connections) The most unfavourable limiting condition shall

be applied when the values of the q factor are determined The values of the q factor

given in the relevant Parts of this Standard are deemed to conform to this requirement.(3)P The structure as a whole shall be checked to ensure that it is stable under the designseismic action Both overturning and sliding stability shall be taken into account Specificrules for checking the overturning of structures are given in the relevant Parts of thisStandard

(4)P It shall be verified that both the foundation elements and the foundation soil are able

to resist the action effects resulting from the response ofthe superstructure withoutsubstantial permanent deformations In determining the reactions, due consideration shall

be given to the actual resistance thatcan be developed by the structural elementtransmitting the actions

(5)P In the analysis the possible influence of second order effects on the values of theaction effects shall be taken into account

(6)P It shall be verified that under the design seismic action the behaviour ofnonstructural elements does not present risks to human and does not have a detrimentaleffect on the response of the structural elements For buildings, specific rules are given in4.3.5 and 4.3.6

2.2.3 Damage limitation state

(1)P An adequate degree of reliability against unacceptable damage shall be ensured bysatisfying the deformation limits or other relevant limits defined in the relevant Parts ofthis Standard.

(2)P In structures important for civil protection the structural system shall be verified toensure that it has sufficient resistance and stiffness to maintain the function of the vitalservices in the facilities for a seismic event associated with an appropriate return period

2.2.4 Specific measures

2.2.4.1 Design

(1) To the extent possible, structures should have simple and regular forms both in planand elevation, (see 4.2.3) If necessary this may be realised by subdividing the structure

by joints into dynamically independent units

(2)P In order to ensure an overall dissipative and ductile behaviour, brittle failure or thepremature formation of unstable mechanisms shall be avoided To this end, whererequired in the relevant Parts of this Standard, resort shall be made to the capacity designprocedure, which is used to obtain the hierarchy of resistance of the various structuralcomponents and failure modes necessary for ensuring a suitable plastic mechanism andfor avoiding brittle failure modes

(3)P Since the seismic performance of a structure is largely dependent on the behaviour

of its critical regions or elements, the detailing of the structure in general and of theseregions or elements inparticular, shall be such as to maintain the capacity to transmit thenecessary forces and to dissipate energy under cyclic conditions To this end, thedetailing of connections between structural elements and of regions where nonlinearbehaviour is foreseeable should receive special care in design

(4)P The analysis shall be based on an adequate structural model, which, when necessary,shall take into account the influence of soil deformability and of nonstructural elementsand other aspects, such as the presence of adjacent structures

2.2.4.3 Quality system plan

(1)P The design documents shall indicate the sizes, the details and the characteristics ofthe materials of the structural elements If appropriate, the design documents shall alsoinclude the characteristics of special devices to be used and the distances betweenstructural and non-structural elements The necessary quality control provisions shall also

(3) In regions of high seismicity and in structures of special importance, formal qualitysystem plans, covering design, construction, and use, additional to the control proceduresprescribed in the other relevant standards, should be used.

3 Ground conditions and seismic action

of such phenomena shall be investigated in accordance with Section 4, Part 2

(4) Depending on the importance class of the structure and the particular conditions of theproject, ground investigations and/orgeological studies should be performed to determinethe seismic action

3.1.2 Identification of ground types

(1) Ground types A, B, C, D, and E, described by the stratigraphic profiles andparameters given in Table 3.1 and described hereafter, may be used to account for theinfluence of local ground conditions on the seismic action This may also be done byadditionally taking into account the influence of deep geology on the seismic action

Table 3.1: Ground types

Cu

(Pa)

A Rock or other rock-like geological

formation, including at most 5 m of

weaker material at the surface

-B Deposits of very dense sand, gravel, or

very stiff clay, at least several tens of

metres in thickness, characterised by a

gradual increase of mechanical

properties with depth

360 - 800 > 50 > 250

C Deep deposits of dense or mediumdense

sand, gravel or stiff clay with thickness

from several tens to many hundreds of

metres

180 - 360 15 - 50 70

-250

D Deposits of loose-to-medium

cohesionless soil (with or without some

soft cohesive layers), or of

predominantly soft-to-firm cohesive soil

< 180 < 15 < 70

E A soil profile consisting of a surface

alluvium layer with vsvalues of type C

or D and thickness varying between

about 5 m and 20 m, underlain by stiffer

material with Vs > 800 m/s

S1 Deposits consisting, or containing a layer

at least 10 m thick, of soft clays/silts

with a high plasticity index (PI >40) and

high water content

< 100(indicative)

S2 Deposits of liquefiable soils, of sensitive

clays, or any other soil profile not

v h v

(4)P For sites with ground conditions matching either one of the two special ground types

S1or S2, special studies for the definition ofthe seismic action are required For these

types, and particularly for S2, the possibility of soil failure under the seismic action shall

be taken into account

NOTE: Special attention should be paid if the deposit is of ground type S1 Such soilstypically have very low values of vs, low internal damping and an abnormally extendedrange of linear behaviour and can therefore produce anomalous seismic site amplificationand soil-structure interaction effects (see Section 6, Part 2) In this case, a special study todefine the seismic action should be carried out, in order to establish the dependence of the

response spectrum on the thickness and Vs value of the soft clay/silt layer and on thestiffness contrast between this layer and the underlying materials

3.2 Seismic action

3.2.1 Seismic zones

(1)P For most of the applications of this Standard, the hazard is described in terms of asingle parameter, i.e the value of the reference peak ground acceleration on type A

ground, agR Additional parameters required for specific types of structures are given inthe relevant Parts of this Standard.

NOTE: The reference peak ground acceleration agR on type A ground is taken from theacceleration zone map of Vietnam, given in Appendix G, Part 1, or may be derived fromseismic zone maps of some territories approved by competent authorities

(2) In this standard document, reference peak ground acceleration agR in Vietnam’s

regions is expressed by isolines Value agR between two isolines is determined by theprinciple of linear interpolation Peak ground acceleration agR can be converted intoearthquake level by MSK-64 scale or MM scale, basing on the table of convertion given

in Section I, Part 1

The reference peak ground acceleration, chosen by the National Authorities for eachseismic zone, corresponds to the reference return period TNCR of the seismic action for theno-collapse requirement (or equivalently the reference probability of exceedance in 50

years, PNCR) (see 2.1(1)P) An importance factor γI equal to 1.0 is assigned to thisreference return period For return periods other than the reference (see importance

classes in 2.1(3)P and (4)), the design ground acceleration on type A ground ag is equal to

agR times the importance factor γI (ag = γI.agR) (See Note to 2.1(4))

Value agR is taken in accordance with Ground Acceleration Zone Map of Vietnam with ratio 1:1 000 000 (Appendix G, Part 1) or Table of Ground Acceleration of

Administrative Locations given in Appendix H, Part 1 (each value of agR given in the table represents the value for the whole region)

(4) In cases of low seismicity, reduced or simplified seismic design procedures for certaintypes or categories of structures may be used

NOTE: A low seismicity case in which the design ground acceleration on type A ground,

ag, is not greater than 0.08g (0.78 m/s2)

(5)P In cases of very low seismicity, the provisions of this Standard need not beobserved

NOTE: A very low seismicity case in which the design ground acceleration on type A

ground, ag, is not greater than 0.04g (0.39 m/s2)

3.2.2 Basic representation of the seismic action

3.2.2.1 General

(1)P Within the scope of this Standard, the earthquake motion at a given point on thesurface is represented by an elastic ground acceleration response spectrum, henceforthcalled an “elastic response spectrum”

(2) The shape of the elastic response spectrum is taken as being the same for the twolevels of seismic action introduced in 2.1(1)P and 2.2.1(1)P for the no-collapserequirement (ultimate limit state – design seismic action) and for the damage limitationrequirement

(3)P The horizontal seismic action is described by two orthogonal components assumed

as being independent and represented by the same response spectrum

(4) For the three components of the seismic action, one or more alternative shapes ofresponse spectra may be adopted, depending on the seismic sources and the earthquakemagnitudes generated from them.

NOTE: In selecting the appropriate shape of the spectrum, consideration should be given

to the magnitude of earthquakes that contribute most to the seismic hazard defined for thepurpose of probabilistic hazard assessment, rather than on conservative upper limits (e.g.the Maximum Credible Earthquake) defined for that purpose

(5) When the earthquakes affecting a site are generated by widely differing sources, thepossibility of using more than one shape of spectra should be considered to enable thedesign seismic action to be adequately represented In such circumstances, different

values of ag will normally be required for each type of spectrum and earthquake

(6) For important structures (γI > 1.0) topographic amplification effects should be takeninto account

NOTE: Appendix A, Part 2 provides information for topographic amplification effects.(7) Time-history representations of the earthquake motion may be used (see 3.2.3)

(8) Allowance for the variation of ground motion in space as well as time may berequired for specific types of structures

3.2.2.2 Horizontal elastic response spectrum

(1)P For the horizontal components of the seismic action, the elastic response spectrum

Se(T) is defined by the following expressions (see Figure 3.1):

e

T S a T S T

5 , 2 ) ( :S T a S

T T

a T S T T

g e

T

T T S

a T S s T

g e

Where:

Se(T) is the elastic response spectrum;;

T is the vibration period of a linear single-degree-of-freedom system;

ag is the design ground acceleration on type A ground (ag = l.agR);

TB is the lower limit of the period of the constant spectral acceleration branch;

TC is the upper limit of the period of the constant spectral acceleration branch;

TD is the value defining the beginning of the constant displacement response range of thespectrum;

S is the soil factor;

 is the damping correction factor with a reference value of η = 1 for 5% viscousdamping, see (3) of this subclause.

(2)P The values of the periods TB, TC and TD and of the soil factor Sdescribing the shape

of the elastic response spectrum depend upon the ground type (See 3.1.2(1))

NOTE 1: For the five ground types A, B, C, D and E, the recommended values of the

parameters S, TB, TC and TD are given in Table 3.2; the standardized spectra, respectively,normalised by ag, for 5% damping are given in Table 3.2

Figure 3.1: Shape of the elastic response spectrum

Table 3.2: Values of the parameters describing the recommended elastic response

Where ξ is the viscous damping ratio of the structure, expressed as a percentage

(4) If for special cases a viscous damping ratio different from 5% is to be used, this value

is given in the relevant Part of this Standard