Eurocode 8: Design of structures for earthquake resistance Part 5: Foundations, retaining structures and geotechnical aspects

Additional rules for the design of various foundation systems, earth retaining structures and soil-structure interaction under seismic actions in conjunction with the structural design of buildings, bridges, towers, masts, chimneys, silos, tanks and pipelines.

Eurocode 8: Auslegung von Bauwerken gegen Erdbeben - Teil 5: Gründungen, Stützbauwerke und geotechnische Aspekte

Eurocode 8: Calcul des structures pour leur résistance aux séismes Partie 5: Fondations, ouvrages de soutenement et aspects géotechniques

Evrokod 8 - Projektiranje potresnoodpornih konstrukcij - 5. del: Temelji, oporne konstrukcije in geotehnični vidiki

General Information

Status
Published
Publication Date
30-Apr-2005
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
01-May-2005
Due Date
01-May-2005
Completion Date
01-May-2005

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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Eurocode 8: Design of structures for earthquake resistance Part 5: Foundations, retaining structures and geotechnical aspectsEurocode 8: Calcul des structures pour leur résistance aux séismes Partie 5: Fondations, ouvrages de soutenement et aspects géotechniquesEurocode 8: Auslegung von Bauwerken gegen Erdbeben - Teil 5: Gründungen, Stützbauwerke und geotechnische AspekteTa slovenski standard je istoveten z:EN 1998-5:2004SIST EN 1998-5:2005en91.120.25YLEUDFLMDPLSeismic and vibration protection91.010.30Technical aspectsICS:SIST ENV 1998-5:1995+D1:19951DGRPHãþDSLOVENSKI
STANDARDSIST EN 1998-5:200501-maj-2005







EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 1998-5
November 2004 ICS 91.120.25 Supersedes ENV 1998-5:1994 English version
Eurocode 8: Design of structures for earthquake resistance Part 5: Foundations, retaining structures and geotechnical aspects
Eurocode 8: Calcul des structures pour leur résistance aux séismes Partie 5: Fondations, ouvrages de soutènement et aspects géotechniques
Eurocode 8: Auslegung von Bauwerken gegen Erdbeben Teil 5: Gründungen, Stützbauwerke und geotechnische Aspekte This European Standard was approved by CEN on 16 April 2004.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36
B-1050 Brussels © 2004 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 1998-5:2004: E



EN 1998-5:2004 (E)2ContentsFOREWORD.41GENERAL.81.1SCOPE.81.2NORMATIVE REFERENCES.81.2.1General reference standards.81.3ASSUMPTIONS.91.4DISTINCTION BETWEEN PRINCIPLES AND APPLICATIONS RULES.91.5TERMS AND DEFINITIONS.91.5.1Terms common to all Eurocodes.91.5.2Additional terms used in the present standard.91.6SYMBOLS.91.7S.I. UNITS.112SEISMIC ACTION.122.1DEFINITION OF THE SEISMIC ACTION.122.2TIME-HISTORY REPRESENTATION.123GROUND PROPERTIES.133.1STRENGTH PARAMETERS.133.2STIFFNESS AND DAMPING PARAMETERS.134REQUIREMENTS FOR SITING AND FOR FOUNDATION SOILS.144.1SITING.144.1.1General.144.1.2Proximity to seismically active faults.144.1.3Slope stability.144.1.3.1General requirements.144.1.3.2Seismic action.144.1.3.3Methods of analysis.154.1.3.4Safety verification for the pseudo-static method.164.1.4Potentially liquefiable soils.164.1.5Excessive settlements of soils under cyclic loads.184.2GROUND INVESTIGATION AND STUDIES.184.2.1General criteria.184.2.2Determination of the ground type for the definition of the seismic action.194.2.3Dependence of the soil stiffness and damping on the strain level.195FOUNDATION SYSTEM.215.1GENERAL REQUIREMENTS.215.2RULES FOR CONCEPTUAL DESIGN.215.3DESIGN ACTION EFFECTS.225.3.1Dependence on structural design.225.3.2Transfer of action effects to the ground.225.4VERIFICATIONS AND DIMENSIONING CRITERIA.235.4.1Shallow or embedded foundations.235.4.1.1Footings (ultimate limit state design).235.4.1.2Foundation horizontal connections.245.4.1.3Raft foundations.255.4.1.4Box-type foundations.255.4.2Piles and piers.266SOIL-STRUCTURE INTERACTION.277EARTH RETAINING STRUCTURES.287.1GENERAL REQUIREMENTS.287.2SELECTION AND GENERAL DESIGN CONSIDERATIONS.287.3METHODS OF ANALYSIS.28



EN 1998-5:2004 (E)37.3.1General methods.287.3.2Simplified methods: pseudo-static analysis.297.3.2.1Basic models.297.3.2.2Seismic action.297.3.2.3Design earth and water pressure.307.3.2.4Hydrodynamic pressure on the outer face of the wall.317.4STABILITY AND STRENGTH VERIFICATIONS.317.4.1Stability of foundation soil.317.4.2Anchorage.317.4.3Structural strength.32ANNEX A (INFORMATIVE) TOPOGRAPHIC AMPLIFICATION FACTORS.33ANNEX B (NORMATIVE) EMPIRICAL CHARTS FOR SIMPLIFIED LIQUEFACTIONANALYSIS.34ANNEX C (INFORMATIVE) PILE-HEAD STATIC STIFFNESSES.36ANNEX D (INFORMATIVE) DYNAMIC SOIL-STRUCTURE INTERACTION (SSI). GENERALEFFECTS AND SIGNIFICANCE.37ANNEX E (NORMATIVE) SIMPLIFIED ANALYSIS FOR RETAINING STRUCTURES.38ANNEX F (INFORMATIVE) SEISMIC BEARING CAPACITY OF SHALLOW FOUNDATIONS.42



EN 1998-5:2004 (E)4ForewordThis European Standard EN 1998–5, Eurocode 8: Design of structures for earthquakeresistance: Foundations, retaining structures and geotechnical aspects, has beenprepared by Technical Committee CEN/TC 250 "Structural Eurocodes", the secretariatof which is held by BSI. CEN/TC 250 is responsible for all Structural Eurocodes.This European Standard shall be given the status of a national standard, either bypublication of an identical text or by endorsement, at the latest by May 2005, andconflicting national standards shall be withdrawn at the latest by March 2010.This document supersedes ENV 1998–5:1994.According to the CEN-CENELEC Internal Regulations, the National StandardOrganisations of the following countries are bound to implement this EuropeanStandard: Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain,Sweden, Switzerland and United Kingdom.Background of the Eurocode programmeIn 1975, the Commission of the European Community decided on an action programmein the field of construction, based on article 95 of the Treaty. The objective of theprogramme was the elimination of technical obstacles to trade and the harmonisation oftechnical specifications.Within this action programme, the Commission took the initiative to establish a set ofharmonised technical rules for the design of construction works which, in a first stage,would serve as an alternative to the national rules in force in the Member States and,ultimately, would replace them.For fifteen years, the Commission, with the help of a Steering Committee withRepresentatives of Member States, conducted the development of the Eurocodesprogramme, which led to the first generation of European codes in the 1980’s.In 1989, the Commission and the Member States of the EU and EFTA decided, on thebasis of an agreement1 between the Commission and CEN, to transfer the preparationand the publication of the Eurocodes to CEN through a series of Mandates, in order toprovide them with a future status of European Standard (EN). This links de facto theEurocodes with the provisions of all the Council’s Directives and/or Commission’sDecisions dealing with European standards (e.g. the Council Directive 89/106/EEC onconstruction products - CPD - and Council Directives 93/37/EEC, 92/50/EEC and89/440/EEC on public works and services and equivalent EFTA Directives initiated inpursuit of setting up the internal market).
1 Agreement between the Commission of the European Communities and the European Committee for Standardisation (CEN)concerning the work on EUROCODES for the design of building and civil engineering works (BC/CEN/03/89).



EN 1998-5:2004 (E)5The Structural Eurocode programme comprises the following standards generallyconsisting of a number of Parts:EN 1990Eurocode :Basis of Structural DesignEN 1991Eurocode 1:Actions on structuresEN 1992Eurocode 2:Design of concrete structuresEN 1993Eurocode 3:Design of steel structuresEN 1994Eurocode 4:Design of composite steel and concrete structuresEN 1995Eurocode 5:Design of timber structuresEN 1996Eurocode 6:Design of masonry structuresEN 1997Eurocode 7:Geotechnical designEN 1998Eurocode 8:Design of structures for earthquake resistanceEN 1999Eurocode 9:Design of aluminium structuresEurocode standards recognise the responsibility of regulatory authorities in eachMember State and have safeguarded their right to determine values related to regulatorysafety matters at national level where these continue to vary from State to State.Status and field of application of EurocodesThe Member States of the EU and EFTA recognise that Eurocodes serve as referencedocuments for the following purposes:– as a means to prove compliance of building and civil engineering works with theessential requirements of Council Directive 89/106/EEC, particularly EssentialRequirement N°1 – Mechanical resistance and stability – and Essential RequirementN°2 – Safety in case of fire ;– as a basis for specifying contracts for construction works and related engineeringservices ;– as a framework for drawing up harmonised technical specifications for constructionproducts (ENs and ETAs)The Eurocodes, as far as they concern the construction works themselves, have a directrelationship with the Interpretative Documents2 referred to in Article 12 of the CPD,although they are of a different nature from harmonised product standards3. Therefore,technical aspects arising from the Eurocodes work need to be adequately considered byCEN Technical Committees and/or EOTA Working Groups working on productstandards with a view to achieving full compatibility of these technical specificationswith the Eurocodes.
2 According to Art. 3.3 of the CPD, the essential requirements (ERs) shall be given concrete form in interpretative documents for thecreation of the necessary links between the essential requirements and the mandates for harmonised ENs and ETAGs/ETAs.3 According to Art. 12 of the CPD the interpretative documents shall :a) give concrete form to the essential requirements by harmonising the terminology and the technical bases and indicating classesor levels for each requirement where necessary ;b) indicate methods of correlating these classes or levels of requirement with the technical specifications, e.g. methods ofcalculation and of proof, technical rules for project design, etc. ;c) serve as a reference for the establishment of harmonised standards and guidelines for European technical approvals.The Eurocodes, de facto, play a similar role in the field of the ER 1 and a part of ER 2.



EN 1998-5:2004 (E)6The Eurocode standards provide common structural design rules for everyday use forthe design of whole structures and component products of both a traditional and aninnovative nature. Unusual forms of construction or design conditions are notspecifically covered and additional expert consideration will be required by the designerin such cases.National Standards implementing EurocodesThe National Standards implementing Eurocodes will comprise the full text of theEurocode (including any annexes), as published by CEN, which may be preceded by aNational title page and National foreword, and may be followed by a National annex.The National annex may only contain information on those parameters which are leftopen in the Eurocode for national choice, known as Nationally Determined Parameters,to be used for the design of buildings and civil engineering works to be constructed inthe country concerned, i.e. :– values and/or classes where alternatives are given in the Eurocode,– values to be used where a symbol only is given in the Eurocode,–
country specific data (geographical, climatic, etc.), e.g. snow map,– the procedure to be used where alternative procedures are given in the Eurocode.It may also contain– decisions on the application of informative annexes,– references to non-contradictory complementary information to assist the user toapply the Eurocode.Links between Eurocodes and harmonised technical specifications (ENs and ETAs)for productsThere is a need for consistency between the harmonised technical specifications forconstruction products and the technical rules for works4. Furthermore, all theinformation accompanying the CE Marking of the construction products which refer toEurocodes shall clearly mention which Nationally Determined Parameters have beentaken into account.Additional information specific to EN 1998-5The scope of Eurocode 8 is defined in EN 1998-1:2004, 1.1.1 and the scope of this Partof Eurocode 8 is defined in 1.1. Additional Parts of Eurocode 8 are listed in EN 1998-1:2004, 1.1.3.
4 see Art.3.3 and Art.12 of the CPD, as well as
4.2, 4.3.1, 4.3.2 and 5.2 of ID 1.



EN 1998-5:2004 (E)7 EN 1998-5:2004 is intended for use by:- clients (e.g. for the formulation of their specific requirements on reliabilitylevels and durability) ;- designers and constructors ;- relevant authorities.For the design of structures in seismic regions the provisions of this European Standardare to be applied in addition to the provisions of the other relevant parts of Eurocode 8and the other relevant Eurocodes. In particular, the provisions of this European Standardcomplement those of EN 1997-1:2004, which do not cover the special requirements ofseismic design.Owing to the combination of uncertainties in seismic actions and ground materialproperties, Part 5 may not cover in detail every possible design situation and its properuse may require specialised engineering judgement and experience.National annex for EN 1998-5This standard gives alternative procedures, values and recommendations for classeswith notes indicating where national choices may have to be made. Therefore theNational Standard implementing EN 1998-5 should have a National annex containingall Nationally Determined Parameters to be used for the design of buildings and civilengineering works to be constructed in the relevant country.National choice is allowed in EN 1998-5:2004 through clauses:ReferenceItem1.1 (4)Informative Annexes A, C, D and F3.1 (3)Partial factors for material properties4.1.4 (11)Upper stress limit for susceptibility to liquefaction5.2 (2)c)Reduction of peak ground acceleration with depth from ground surface



EN 1998-5:2004 (E)81 GENERAL1.1 Scope(1)PThis Part of Eurocode 8 establishes the requirements, criteria, and rules for thesiting and foundation soil of structures for earthquake resistance. It covers the design ofdifferent foundation systems, the design of earth retaining structures and soil-structureinteraction under seismic actions. As such it complements Eurocode 7 which does notcover the special requirements of seismic design.(2)PThe provisions of Part 5 apply to buildings (EN 1998-1), bridges (EN 1998-2),towers, masts and chimneys (EN 1998-6), silos, tanks and pipelines (EN 1998-4).(3)PSpecialised design requirements for the foundations of certain types ofstructures, when necessary, shall be found in the relevant Parts of Eurocode 8.(4)Annex B of this Eurocode provides empirical charts for simplified evaluation ofliquefaction potential, while Annex E gives a simplified procedure for seismic analysisof retaining structures.NOTE 1 Informative Annex A provides information on topographic amplification factors.NOTE 2 Informative Annex C provides information on the static stiffness of piles.NOTE 3 Informative Annex D provides information on dynamic soil-structure interaction.NOTE 4 Informative Annex F provides information on the seismic bearing capacity of shallowfoundations.1.2 Normative references(1)PThis European Standard incorporates by dated or undated reference, provisionsfrom other publications. These normative references are cited at the appropriate placesin the text and the publications are listed hereafter. For dated references, subsequentamendments to or revisions of any of these publications apply to this European Standardonly when incorporated in it by amendment or revision. For undated references thelatest edition of the publication referred to applies (including amendments).1.2.1 General reference standardsEN 1990Eurocode - Basis of structural designEN 1997-1Eurocode 7 - Geotechnical design – Part 1: General rulesEN 1997-2Eurocode 7 - Geotechnical design – Part 2: Ground investigation andtestingEN 1998-1Eurocode 8 - Design of structures for earthquake resistance – Part 1:General rules, seismic actions and rules for buildingsEN 1998-2Eurocode 8 - Design of structures for earthquake resistance – Part 2:Bridges



EN 1998-5:2004 (E)9EN 1998-4Eurocode 8 - Design of structures for earthquake resistance – Part 4:Silos, tanks and pipelinesEN 1998-6Eurocode 8 - Design of structures for earthquake resistance – Part 6:Towers, masts and chimneys1.3 Assumptions(1)PThe general assumptions of EN 1990:2002, 1.3 apply.1.4 Distinction between principles and applications rules(1)PThe rules of EN 1990:2002, 1.4 apply.1.5 Terms and definitions1.5.1 Terms common to all Eurocodes(1)PThe terms and definitions given in EN 1990:2002, 1.5 apply.(2)PEN 1998-1:2004, 1.5.1 applies for terms common to all Eurocodes.1.5.2 Additional terms used in the present standard(1)PThe definition of ground found in EN 1997-1:2004, 1.5.2 applies while that ofother geotechnical terms specifically related to earthquakes, such as liquefaction, aregiven in the text.(2)For the purposes of this standard the terms defined in EN 1998-1:2004, 1.5.2apply.1.6 Symbols(1)For the purposes of this European Standard the following symbols apply. Allsymbols used in Part 5 are defined in the text when they first occur, for ease of use. Inaddition, a list of the symbols is given below. Some symbols occurring only in theannexes are defined therein:EdDesign action effectEpdLateral resistance on the side of footing due to passive earth pressureEREnergy ratio in Standard Penetration Test (SPT)FHDesign seismic horizontal inertia forceFVDesign seismic vertical inertia forceFRdDesign shear resistance between horizontal base of footing and the groundGShear modulusGmaxAverage shear modulus at small strainLeDistance of anchors from wall under dynamic conditionsLsDistance of anchors from wall under static conditions



EN 1998-5:2004 (E)10MEdDesign action in terms of momentsN1(60)SPT blowcount value normalised for overburden effects and for energy ratioNEdDesign normal force on the horizontal baseNSPTStandard Penetration Test (SPT) blowcount valuePIPlasticity Index of soilRdDesign resistance of the soilSSoil factor defined in EN 1998-1:2004, 3.2.2.2STTopography amplification factorVEdDesign horizontal shear forceWWeight of sliding massagDesign ground acceleration on type A ground (ag = γI agR)agRReference peak ground acceleration on type A groundavgDesign ground acceleration in the vertical directionc′Cohesion of soil in terms of effective stresscuUndrained shear strength of soildPile diameterdrDisplacement of retaining wallsgAcceleration of gravitykhHorizontal seismic coefficientkvVertical seismic coefficientquUnconfined compressive strengthrFactor for the calculation of the horizontal seismic coefficient (Table 7.1)vsVelocity of shear wave propagationvs,maxAverage vs value at small strain ( < 10-5)αRatio of the design ground acceleration on type A ground, ag, to the accelerationof gravity gγUnit weight of soilγdDry unit weight of soilγIImportance factorγMPartial factor for material propertyγRdModel partial factorγw Unit weight of waterδFriction angle between the ground and the footing or retaining wallφ′Angle of shearing resistance in terms of effective stressρUnit mass



EN 1998-5:2004 (E)11σvoTotal overburden pressure, same as total vertical stressσ′voEffective overburden pressure, same as effective vertical stressτcy,uCyclic undrained shear strength of soilτeSeismic shear stress1.7 S.I. Units(1)PS.I. Units shall be used in accordance with ISO 1000.(2)In addition the units recommended in EN 1998-1:2004, 1.7 apply.NOTE For geotechnical calculations, reference should be made to EN 1997-1:2004, 1.6 (2).



EN 1998-5:2004 (E)122 SEISMIC ACTION2.1 Definition of the seismic action(1)PThe seismic action shall be consistent with the basic concepts and definitionsgiven in EN 1998-1:2004, 3.2 taking into account the provisions given in 4.2.2.(2)PCombinations of the seismic action with other actions shall be carried outaccording to EN 1990:2002, 6.4.3.4 and EN 1998-1:2004, 3.2.4.(3) Simplifications in the choice of the seismic action are introduced in thisEuropean Standard wherever appropriate.2.2 Time-history representation(1)PIf time-domain analyses are performed, both artificial accelerograms and realstrong motion recordings may be used. Their peak value and frequency content shall beas specified in EN 1998-1:2004, 3.2.3.1.(2)In verifications of dynamic stability involving calculations of permanent grounddeformations the excitation should preferably consist of accelerograms recorded on soilsites in real earthquakes, as they possess realistic low frequency content and proper timecorrelation between horizontal and vertical components of motion. The strong motionduration should be selected in a manner consistent with EN 1998-1:2004, 3.2.3.1.



EN 1998-5:2004 (E)133 GROUND PROPERTIES3.1 Strength parameters(1)The value of the soil strength parameters applicable under static undrainedconditions may generally be used. For cohesive soils the appropriate strength parameteris the undrained shear strength cu, adjusted for the rapid rate of loading and cyclicdegradation effects under the earthquake loads when such an adjustment is needed andjustified by adequate experimental evidence. For cohesionless soil the appropriatestrength parameter is the cyclic undrained shear strength τcy,u which should take thepossible pore pressure build-up into account.(2)Alternatively, effective strength parameters with appropriate pore water pressuregenerated during cyclic loading may be used. For rocks the unconfined compressivestrength, qu , may be used.(3)The partial factors (γM) for material properties cu, τcy,u and qu are denoted as γcu,γτcy and γqu, and those for tan φ′ are denoted as γφ′.NOTE The values ascribed to γcu, γτcy, γqu, and γφ′ for use in a country may be found in its NationalAnnex. The recommended values are γcu = 1,4, γτcy = 1,25, γqu = 1,4, and γφ′ = 1,25.3.2 Stiffness and damping parameters(1)Due to its influence on the design seismic actions, the main stiffness parameterof the ground under earthquake loading is the shear modulus G, given by2sρν=G(3.1)where ρ is the unit mass and vs is the shear wave propagation velocity of the ground.(2)Criteria for the determination of vs, including its dependence on the soil strainlevel, are given in 4.2.2 and 4.2.3.(3)Damping should be considered as an additional ground property in the caseswhere the effects of soil-structure interaction are to be taken into account, specified inSection 6.(4)Internal damping, caused by inelastic soil behaviour under cyclic loading, andradiation damping, caused by seismic waves propagating away from the foundation,should be considered separately.



EN 1998-5:2004 (E)144 REQUIREMENTS FOR SITING AND FOR FOUNDATIONSOILS4.1 Siting4.1.1 General(1)PAn assessment of the site of construction shall be carried out to determine thenature of the supporting ground to ensure that hazards of rupture, slope instability,liquefaction, and high densification susceptibility in the event of an ea
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