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DRAFT FOR DEVELOPMENT DD ENV1992-1-5:1996

Eurocode 2:Design of concrete

structures

Part 1.5 General rules Structures with unbonded and external

prestressing tendons

(together with United KingdomNational Application Document)

ICS 91.040; 91.080.40

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This Draft for Development,having been prepared underthe direction of the SectorBoard for Building and CivilEngineering, was publishedunder the authority of theStandards Board and comesinto effect on15 September 1996

BSI 02-2000

The following BSI reference

relates to the work on thisDraft for Development:Committee reference B/525/2

ISBN 0 580 25822 X

Committees responsible for thisDraft for Development

The preparation of this Draft for Development was entrusted by Technical

Committee B/525, to BSI Subcommittee B/525/2, Structural use of concrete,upon which the following bodies were represented:

Association of Consulting EngineersBritish Cement AssociationBritish Precast Concrete Federation Ltd.Department of the Environment (Property and Buildings Directorate)Department of Transport (Highways Agency)Federation of Civil Engineering ContractorsInstitution of Civil EngineersInstitution of Structural Engineers

Steel Reinforcement Commission

Amendments issued since publication

Amd. No. Date Comments




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Contents

PageCommittees responsible Inside front cover

National foreword iiForeword 2Text of National Application Document iiiText of ENV 1992-1-5 5




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National foreword

This Draft for Development was prepared by Subcommittee B/525/2 and is theEnglish language version of ENV 1992-1-5:1994 Eurocode 2: Design of concretestructures Part 1.5: General rules Structures with unbonded and external

prestressing tendons,as published by the European Committee forStandardization (CEN). This Draft for Development also includes the UnitedKingdom (UK) National Application Document (NAD) to be used with the ENV inthe design of buildings to be constructed in the UK.ENV 1992-1-5 results from a programme of work sponsored by the EuropeanCommission to make available a common set of rules for the structural andgeotechnical design of building and civil engineering works.This publication is not to be regarded as a British Standard.

An ENV is made available for provisional application, but does not have thestatus of a European Standard. The aim is to use the experience gained to modifythe ENV so that it can be adopted as a European Standard. The publication of thisENV and its National Application Document should be considered to supersede

any reference to a British Standard in previous DD ENV Eurocodes concerningthe subject covered by these documents.The values for certain parameters in the ENV Eurocodes may be set by individualCEN Members so as to meet the requirements of national regulations. Theseparameters are designated by |_| in the ENV.During the ENV period of validity, reference should be made to the supportingdocuments listed in the National Application Document (NAD).The purpose of the NAD is to provide essential information, particularly inrelation to safety, to enable the ENV to be used for buildings constructed in theUK and the NAD takes precedence over corresponding provisions in the ENV.The Building Regulations 1991, Approved Document A 1992, draws attention tothe potential use of ENV Eurocodes as an alternative approach to Building

Regulation compliance. ENV 1992-1-5 is considered to offer such an alternativeapproach, when used in conjunction with its NAD.Users of this document are invited to comment on its technical content, ease ofuse and any ambiguities or anomalies. These comments will be taken into accountwhen preparing the UK national response to CEN on the question of whether theENV can be converted to an EN.Comments should be sent in writing to the Secretary of Subcommittee B/525/2,BSI, 389 Chiswick High Road, London W4 4AL, quoting the document reference,the relevant clause and, where possible, a proposed revision, by 31 October 1996.

Summary of pages

This document comprises a front cover, an inside front cover, pages i to vi,the ENV title page, pages 2 to 14 and a back cover.This standard has been updated (see copyright date) and may have hadamendments incorporated. This will be indicated in the amendment table on theinside front cover.




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National Application

Document

for use in the UK with

ENV 1992-1-5:1994




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Contents ofNational Application Document

Page

Introduction v1 Scope v2 Partial factors, combination factors and other values v3 Reference standards vTable 1 References in EC2-1.5 to other codes and standards v




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Introduction

This National Application Document (NAD) has been prepared by Subcommittee B/525/2. It has beendeveloped from the following.

a) A textual examination of ENV 1992-1-5.b) A parametric calibration against BS 8110, supporting standards and test data.c) Trial calculations.

1 Scope

This NAD provides information to enable ENV 1992-1-5 (hereafter referred to as EC2-1.5) to be used forthe design of buildings to be constructed in the UK. It will be assumed that it will be used in conjunctionwith DD ENV 1992-1-1, the NAD of which refers to BSI publication for values of actions.

2 Partial factors, combination factors and other values

a) The values for combination coefficients () should be those given in Table 1 of the NAD for EC2-1.1.b) The values for partial factors for normal temperature design should be those given in EC2-1.1, exceptwhere modified by the NAD for that code.c) Other values should be those given in EC2-1.1, except where modified by the NAD for that code,and EC2-1.5.

3 Reference standards

Supporting standards including materials specifications and standards for construction are listedin Table 1 of this NAD.

Table 1 Reference in EC2-1.5 to other codes and standards

Referencein EC2-1.5

Documentreferred to

Document title or subject area Status UK document

Various ENV 1992-1-1 Design of Concrete structures.General rules and rules forbuildings

Published 1991 DD ENV 1992-1-1:1992




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Foreword

Objectives of the Eurocodes(1) The Structural Eurocodes comprise a group ofstandards for the structural and geotechnical designof buildings and civil engineering works.(2) They cover execution and control only to theextent that is necessary to indicate the quality of theconstruction products, and the standard of theworkmanship needed to comply with theassumptions of the design rules.(3) Until the necessary set of harmonized technicalspecifications for products and for the methods oftesting their performance are available, some of the

Structural Eurocodes cover some of these aspects ininformative Annexes.

Background to the Eurocodeprogramme

(4) The Commission of the European Communities(CEC) initiated the work of establishing a set ofharmonized technical rules for the design ofbuilding and civil engineering works which wouldinitially serve as an alternative to the different rulesin force in the various Member States and wouldultimately replace them. These technical rulesbecame known as the Structural Eurocodes.

(5) In 1990, after consulting their respectiveMember States, the CEC transferred the work offurther development, issue and updating of theStructural Eurocodes to CEN, and the EFTASecretariat agreed to support the CEN work.(6) CEN Technical Committee CEN/TC250 isresponsible for all Structural Eurocodes

Eurocode programme

(7) Work is in hand on the following StructuralEurocodes, each generally consisting of a number ofparts:

EN 1991, Eurocode 1: Basis of design and actionson structures.EN 1992, Eurocode 2: Design of concretestructures.EN 1993, Eurocode 3: Design of steel structures.EN 1994, Eurocode 4: Design of composite steeland concrete structures.EN 1995, Eurocode 5: Design of timberstructures.EN 1996, Eurocode 6: Design of masonrystructures.EN 1997, Eurocode 7: Geotechnical design.

EN 1998, Eurocode 8: Design provisions forearthquake resistance of structures.

EN 1999, Eurocode 9: Design of aluminium alloystructures.

(8) Separate sub-committees have been formed byCEN/TC250 for the various Eurocodes listed above.(9) This Part 1-5 of Eurocode 2 is being published asa European Prestandard (ENV) with an initial life ofthree years.(10) This Prestandard is intended for experimentalapplication and for the submission of comments.(11) After approximately two years CEN memberswill be invited to submit formal comments to betaken into account in determining future actions.(12) Meanwhile feedback and comments on thisPrestandard should be sent to the Secretariat of

CEN/TC250/SC2 at the following address:Deutsches Institut fr Normung e.V. (DIN)Burggrafenstrasse 6D 10787 Berlinphone: (+ 49) 30 26 01 25 01fax: (+ 49) 30 26 01 12 31

or to your national standards organization.

National application documents(NADS)

(13) In view of the responsibilities of authorities in

member countries for safety, health and othermatters covered by the essential requirements ofthe Construction Products Directive (CPD), certainsafety elements in this ENV have been assignedindicative values which are identified by [ ] (boxedvalues). The authorities in each member countryare expected to assign definitive values to thesesafety elements.(14) Some of the supporting European orInternational Standards may not be available by thetime this Prestandard is issued. It is thereforeanticipated that a National Application Document(NAD) giving definitive values for safety elements,

referencing compatible supporting standards andproviding national guidance on the application ofthis Prestandard, will be issued by each membercountry or its Standards Organization.(15) It is intended that this Prestandard is used inconjunction with the NAD valid in the countrywhere the building or civil engineering works islocated.




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Matters specific to this prestandard

(16) The scope of Eurocode 2 is defined in 1.1.1of

ENV 1992-1-1 and the scope of this Part ofEurocode 2 is defined in 1.1.2. Additional Parts ofEurocode 2 which are planned are indicated in 1.1.3of ENV 1992-1-1; these will cover additionaltechnologies or applications, and will complementand supplement this Part.(17) In using this Prestandard in practice,particular regard should be paid to the underlyingassumptions and conditions given in 1.3ofENV 1992-1-1.(18) The seven chapters of this Prestandard arecomplemented by four Appendices which have the

same normative status as the chapters to whichthey relate. These Appendices have beenintroduced by moving some of the more detailedPrinciples/Application Rules, which are needed inparticular cases, out of the main part of the text toaid its clarity.(19) As indicated in paragraph (14) of this Foreword,reference should be made to National ApplicationDocuments which will give details of compatiblesupporting standards to be used. For this Part ofEurocode 2, particular attention is drawn to theapproved Prestandard ENV 206 (Concrete performance, production, placing and compliance

criteria), and the durability requirements givenin 4.1of this Prestandard.(20) The provisions of this Prestandard are basedsubstantially on the 1978 edition of the CEB ModelCode and other more recent CEB and FIPdocuments.(21) In developing this Prestandard, backgrounddocuments have been prepared, which givecommentaries on and justifications for some of theprovisions in this Prestandard.For ENV 1992-1-5, the following additionalsub-clauses apply:

(22) This Part 1-5 of Eurocode 2 complementsENV 1992-1-1 for the particular aspects ofstructures with unbonded and external tendons.(23) The framework and structure of this Part 1-5correspond to ENV 1992-1-1. However, Part 1-5contains Principles and Application Rules which arespecific to structures with unbonded and externaltendons.(24) Where a particular sub-clause of ENV 1992-1-1is not mentioned in this ENV 1992-1-5, thatsub-clause of ENV 1992-1-1 applies as far asdeemed appropriate in each case.

Some Principles and Application Rules ofENV 1992-1-1 are modified or replaced in this Part,in which case they are superseded.

Where a Principle or Application Rule inENV 1992-1-1 is modified or replaced, the new

number is identified by the addition of 100 to theoriginal number. Where a new Principle orApplication Rule is added, it is identified by anumber which follows the last number ofENV 1992-1-1 with 100 added to it.A subject not covered by ENV 1992-1-1 is introducedin this Part by a new sub-clause. The sub-clausenumber for this follows the most appropriate clausenumber in ENV 1992-1-1.(25) The numbering of equations, figures, footnotesand tables in this Part follow the same principles asthe clause numbering in (24) above.

(26) Prestressing with unbonded tendons, being thesubject of this ENV 1992-1-5, brings forward twodistinct technologies:

prestressing with small tendons, generallymonostrands, installed in a plastic sheath of asmall diameter embedded in concrete; prestressing with larger tendons, locatedoutside the concrete, generally inside a box-girderor between the webs of multiple girderstructures.

(27) The former are normally used in floors forbuildings, while the specific field of application ofthe second technology is in bridge construction.However, their use is not restricted, since on the onehand certain road bridge decks may be reinforcedwith unbonded internal tendons and, on the otherhand, external prestressing has often beenimplemented in the construction of beams made ofprefabricated segments for industrial buildings.(28) Attention is drawn to the specificcharacteristics of external prestressing. Certaincalculation models which are referred to inENV 1992-1-1 must be discarded and replaced bynew models, the validity of which has to beestablished. Where necessary, relevant indications

are given in this Part 1-5 of ENV 1992.




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Contents

PageForeword 21 Introduction 51.1 Scope 51.1.2 Scope of part 1-5 of Eurocode 2 51.4 Definitions 51.4.2 Special terms used in part 1-5 of

Eurocode 2 51.7 Special symbols used in this part 1-5

of Eurocode 2 51.7.3 Latin lower case symbols 5

1.7.4 Greek symbols 52 Basis of design 62.3 Design requirements 62.3.2 Ultimate limit states 62.3.2.2 Combinations of actions 62.5 Analysis 62.5.3 Calculation methods 62.5.3.1 Basic considerations 63 Material properties 63.3 Prestressing steel 6

3.3.6 Prestressing steel in internalunbonded tendons 63.4 Prestressing devices 73.4.2 Tubes for external tendons 73.4.2.1 General 73.4.3 External unbonded tendons 83.4.3.1 General 83.4.3.2 Anchorages 83.4.4 Internal unbonded tendons 83.4.4.1 General 83.4.5 Deviators 8

3.4.5.1 General 84 Section and member design 94.2 Design data 94.2.3 Prestressed concrete 94.2.3.5 Design of members in

prestressed concrete 94.3 Ultimate limit states 104.3.1 Ultimate limit states for bending

and longitudinal force 104.3.1.4 External tendons 10

4.3.1.5 Internal unbonded tendons 104.3.2 Shear 104.3.2.6 Segmental construction 10

Page4.4 Serviceability limit states 11

4.4.0 General 114.4.0.3 Load cases and combinations 114.4.1 Limitation of stresses under

serviceability conditions 114.4.1.1 Basic considerations 114.4.2 Limit states of cracking 114.4.2.1 General considerations 114.4.2.2 Minimum reinforcement areas 114.4.2.3 Control of cracking without

direct calculation 124.4.2.4 Calculation of crack width 125 Detailing provisions 125.3 Prestressing units 125.3.1 Arrangement of the prestressing units 125.3.2 Concrete cover 125.5 Limitation of damage due to

accidental action 135.5.2 Proportioning of ties 136 Construction and workmanship 137 Quality control 13Appendix 1 Additional provisions for the

determination of the effects of time-dependentdeformation of concrete 14Appendix 2 Non-linear analysis 14Appendix 3 Supplementary information onthe ultimate limit states induced by structuraldeformation 14Appendix 4 Checking deflections by calculations 14Table 3.105 Minimum radii of deviationin the anchorage zone 8Table 3.106 Minimum radii of deviationin the deviation zone 9Table 4.115 Friction coefficient fordifferent type of unbonded tendon 9




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1 Introduction

This clause of ENV 1992-1-1 is applicable except as follows:

1.1 Scope

1.1.2 Scope of part 1-5 of Eurocode 2

1.4 Definitions

1.4.2 Special terms used in part 1-5 of Eurocode 2

1.7 Special symbols used in this part 1-5 of Eurocode 2

1.7.3 Latin lower case symbols

1.7.4 Greek symbols

Addition after Principle P(5):P(106) This Part 1-5 of Eurocode 2 gives a general basis for the design of reinforced concrete

components provided with unbonded tendons placed within or outside the concrete. In addition,this Part 1-5 gives design rules which are mainly applicable to buildings. This Part 1-5 does notapply to structures subjected to significant fatigue under variable loads. It does also not apply tostructures with tendons temporarily ungrouted during construction [see ENV 1992-1-1,Clauses 1.4.2 P(2) and 2.5.4.1 (4)].This ENV 1992-1-5 does not apply to members prestressed by tendons located outside theenvelope of the concrete structure.

P(107) This Part 1-5 applies to concrete cast in situ or to precast units. Joints may be either reinforcedcrossed by reinforcement or unreinforced with or without glueing or sealing compound.

P(108) All clauses of ENV 1992-1-1 are generally applicable to the structures covered by this Part 1-5provided that the relevant detailing provisions are fulfilled and the actions of the tendons areconsidered as external forces.

P(109) For the design of members with unreinforced joints, the design models shall take into accountthe geometrical and mechanical consequences of the opening of the joints.

Addition after Principle P(2):P(103) External tendon: A post-tensioned tendon situated outside the concrete section but inside the

envelope of the concrete structure, only connected to the structure by anchorages and deviators.P(104) Deviator: A device (e.g. concrete block, steel assembly or cross beam) round which a tendon is

bent and where the tendon exerts a radial force on the structure.P(105) Internal unbonded tendon: A cast-in post-tensioned tendon, fabricated from sheathed

prestressing strands or steels, connected to the structure by anchorages only.P(106) Sheathed prestressing strand: Grease coated prestressing strand inside a tube-like plastic

sheathing, in which it can move freely in the longitudinal direction (monostrand).

r Radius of the outline of a curved unbonded prestressing tendont Thickness of a steel tube used as sheathing

Coefficient of friction between an unbonded tendon and ducts1 Unintentional angular displacement (per unit length) related to the profile of the unbonded tendons

Outer diameter of the sheathing of the unbonded prestressing tendon




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2 Basis of design


2.3 Design requirements

2.3.2 Ultimate limit states

2.3.2.2 Combination of actions

2.5 Analysis

2.5.3 Calculation methods

2.5.3.1Basic considerations

3 Material properties


3.3 Prestressing steel

Additional clauses after 3.3.5.3 (2):

3.3.6 Prestressing steel in internal unbonded tendons

Replacement of Principle P(1) by:P(101) For each load case, design values Edfor the effects of actions shall be determined from

combination rules involving design values of actions as identified by Table 2.1 inENV 1992-1-1.The combinations of actions given in clause 2.3.2.2of ENV 1992-1-1 apply also to structureswith unbonded and external prestressing tendons.

Addition after Application Rule (5):P(106) The methods of analysis given in clause 2.5.3of ENV 1992-1-1 may be applied under the

following restrictions: if reinforcement is needed to ensure the structural ductility, the unbonded tendons shall not

be taken into account and their effect shall be considered as an external force; no redistribution of moments and forces is permitted for structures composed of

prefabricated segments with unreinforced contact joints.(107) It is convenient to determine the effects of prestressing by replacing each tendon by a set of

physical forces it exerts on the concrete as follows: concentrated forces at anchorages; radial distributed forces of intensity Pm/r, r being the curvature radius of the centreline

of tendon and Pmthe mean value of the prestressing force (see ENV 1992-1-1, 2.5.4.2);

tangential distributed forces of intensity dPm/ds, ds being the increment of thecurvilinear abscissa along the outline, and dPmis the rate of increase of tendon forcealong its centreline.

(108) For internal tendons in structures of buildings, it may be assumed that: the force in a tendon is constant all along a span; for a horizontal member the distributed radial forces are vertical for tendons deviated in

the vertical plane; the tendons outline comprises of straight or parabolic segments.

(109) Along the free lengths between deviators the tendon may be considered as straight.

P(101) The prestressing steel in internal unbonded tendons shall be adequately and permanentlyprotected against corrosion.




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3.4.3 External unbonded tendons

3.4.3.1 General

3.4.3.2Anchorages

Table 3.105 Minimum radii of deviation in the anchorage zone

3.4.4 Internal unbonded tendons

3.4.4.1 General

3.4.5 Deviators

3.4.5.1 General


P(101) An external unbonded tendon is a tendon situated outside the original concrete section and isconnected to the structure by anchorages and deviators only.

P(102) The post-tensioning system shall receive a specific approval by relevant authorities for the useas external tendons.(103) In anchorage zones, the tendon is usually embedded in a concrete bulkhead, blister or

steel assembly.(104) The deviators may consist of concrete blocks, steel assemblies or cross beams. In the

deviators, the tendon is bent and exerts a radial pressure.(105) The anchorages and deviators should enable removal of the tendon without damaging

the structural elements, unless stated otherwise in the project specification.

(101) In the absence of indication in the approval documents of the system, the minimum radius ofcurvature of the tendon in the anchorage zone beyond the anchor plate may be taken fromTable 3.105.

UnitsMinimum Radius

(m)Strands Wires

1913 mm or 1215 mm 54 7 mm 3.5

3113 mm or 1915 mm 91 7 mm 4.05513 mm or 3715 mm 140 7 mm 5.0

Linear interpolation between the values in Table 3.105 is permitted.

P(101) An unbonded internal tendon-consists of one or several wires, strands or bars encased in aflexible and watertight sheath embedded in concrete in which they are free to movelongitudinally as the void between the sheath and the prestressing steel is filled with alubricating material.

P(102) The prestressing steel shall be permanently protected against corrosion throughout its length

including in the anchorage zones.P(103) The post-tensioning system shall receive specific approval by relevant authorities for its use

with internal tendons.(104) The sheath may be of polyethylene or polypropylene or other non-corrosive material. The

lubricating material may be a non-corrosive grease.

P(101) A deviator shall satisfy the following requirements: withstand both longitudinal and transverse forces that the tendon applies to it and transmit

these forces to the structure;

ensure without unacceptable angular discontinuity the connection between two straightsections of the tendon.




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Table 3.106 Minimum radii of deviation in the deviation zone

4 Section and member design

This clause of ENV 1992-1-1 applies except as follows:

4.2 Design data

4.2.3 Prestressed concrete

4.2.3.5Design of members in prestressed concrete4.2.3.5.5 Loss of prestress

Table 4.115 Friction coefficient for differenttype of unbonded tendon

(102) In the deviation zones, the tubes forming the sheaths may be made of steel or HDPE,provided in the latter case that it has been demonstrated that they are able to sustain the

radial pressure and longitudinal movement of the tendon, without damage and withoutimpairing its proper functioning. If made of steel, the sheaths should be prebent to theradius specified by the design.

(103) In the absence of a requirement in the approval documents of the system, the radius ofcurvature of the tendon in a deviation zone may be taken from Table 3.106:

UnitsMinimum Radius

(m)Strands Wires

1913 mm or 1215 mm 54 7 mm 2.5

3113 mm or 1915 mm 91 7 mm 3.0

5513 mm or 3715 mm 140 7 mm 5.0

Linear interpolation between the values in Table 3.106 is permitted.

(104) Designed tendon deviations up to an angle of |0.02| rad are permitted without particulardeviation saddle, as specified in the approval documents. The forces developed in thedeviation should be taken into account in the design calculations.

Addition after Application Rule (11):(112) For tendons external to the concrete consisting of parallel wires or strands, the loss of

prestress due to unintentional angular displacements may be neglected.(113) For external tendons, in the absence of more exact data, the values of the coefficient of

frictionmay be taken from the Table 4.115 below:

Coefficient of friction, Steel tube HDPE tube

Lubricated strands 0.18 0.12Lubricated wires 0.16 0.10

Non lubricated strands 0.25 0.14

Non lubricated wires 0.24 0.12

(114) For internal grease-coated monostrands, in the absence of more exact data, the coefficientof friction between the strands and their sheaths and the unintentional angulardisplacement 1may be assumed to have the following values:

= |0.05| = |0.06| rad/m.




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4.3 Ultimate limit-states

4.3.1 Ultimate limit states for bending and longitudinal force


4.3.1.4 External tendons

4.3.1.5 Internal unbonded tendons

4.3.2 Shear


4.3.2.6 Segmental construction

(115) For the calculation of the time dependent losses in an unbonded tendon, theequation (4.10) in clause 4.2.3.5.5of ENV 1992-1-1 applies, provided the values of the

shrinkage and creep strains of concrete are taken as mean values: along the straight part of the tendon including the considered abscissa for and external

tendon, along the entire length of the tendon, if internal.

P(101) For external tendons, the strain of the prestressing steel at the ultimate limit state is constant

between two successive points of contact with the structure (anchorages or deviators).P(102) In the ultimate limit state for bending and longitudinal force, the strain of the prestressing steelis equal to the pre-strain as defined in clause 2.5.4.4.3of ENV 1992-1-1, increased by the meanconcrete strain between two successive fixation points [see ENV 1992-1-1, 4.3.1.2 (5)].(103) If, for simplification, instead of a non-linear analysis of the structure as a whole a

sectional verification based on a linear analysis is performed, the increase in strain ofthe prestressing steel should be neglected.

(104) For the verification at the ultimate limit states the partial factor*Paccording toTable 2.2 in clause 2.3.3.1of ENV 1992-1-1 should be applied to the prestressing forcesdetermined according to P(101), P(102) and (103) above.

P(105) Measures shall be taken to maintain a constant relative position of the tendon within theconcrete section in a sufficient number of sections in order to avoid harmful second order effects.

(101) In the absence of any specific requirement for checking at the ultimate limit state forbending and longitudinal force, for normal buildings [see clause 1.1.2P(2) inENV 1992-1-1], it may be assumed that the increase in stress in tendons of a length notexceeding a single span is equal to 100 N/mm2. Where the tendon length is greater, thisvalue should be reduced taking account of the number of spans and the acting loads.

P(101) For the design of segments with unreinforced joints, the rules for reinforced concrete apply; theinternal stress in the joints shall be modelled as external forces acting on the concrete segment.P(102) The unreinforced joints shall satisfy the relevant conditions of force transfer. The transmission

shall be assumed to act only in the compressed joint area. The transmission of the shear forcethrough the unreinforced joints shall be assumed as external forces acting on the concretesegment.

Attention shall be drawn to the rapid decrease of the depth of the compressive zone in case of increase ofthe bending moment.

(103) For simplification, in normal buildings, the longitudinal force in an unreinforced jointmay be assumed to act at the centroid of the compressed parts of the section.

(104) Under consideration of the most unfavourable action [acc. to equation [2.7 (a)] inENV 1992-1-1] and in the absence of justification by former experience, unreinforced joint

sections should be compressed over at least |2/3| of their total depth. Special attentionshould be given to torsion effects in the design of hollow sections.




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4.4 Serviceability limit states

4.4.0 General

Additional clauses after 4.4.0.2P(1):

4.4.0.3 Load cases and combinations

4.4.1 Limitation of stresses under serviceability conditions

4.4.1.1Basic considerations

4.4.2 Limit states of cracking4.4.2.1 General considerations

4.4.2.2Minimum reinforcement areas

(101) In addition to the combinations of actions defined in clause 2.3.4of ENV 1992-1-1, atemperature difference of | 10| K should be taken into account between an externaltendon and the concrete structure. Where tendons are exposed to direct solar irradiation,special considerations may be necessary.

(102) As a simplification, when checking the serviceability limit states, it may be assumed inthe analysis, that the concrete remains uncracked.

(103) For the calculation of the force in the external tendons due to variable actions, thedeviators may be considered as fixed points (no longitudinal relative displacement

between the tendon and the concrete structure).

Replacement of Application Rule (4) by:(104) Where all tendons are external or internal and unbonded, the member should be

considered as reinforced only and the rules specific to prestressed concrete givenin 4.4.1.1 (4) of ENV 1992-1-1 do not apply. Therefore, the rules for reinforced concreteapply with regard to durability.For externally prestressed members with unreinforced concrete joints, see 4.4.2.1 (110)below.

Replacement of application Rule (7) by:(107) For prestressed members with bonded and unbonded tendons, 4.4.2.1 (7) in ENV 1992-1-1

applies.However, where all tendons are external or internal and unbonded, the rules specific toprestressed concrete in 4.4.2.1of ENV 1992-1-1 do not apply. The rules for reinforcedconcrete apply with regard to durability.

Addition after Principle P(9):(110) For externally prestressed members with unreinforced contact joints, concrete

stressesBc > |0| (e.g. exceedance of the limit state of decompression) should not be

allowed in the joint sections under the rare combinations of actions as definedin 2.3.4 P(2) of ENV 1992-1-1. For this verification, the prestressing force may be taken asthe mean value Pm.

Addition after Application Rule (8):(109) For externally prestressed members cast in-situ or with reinforced joints, and for

internally prestressed members using unbonded tendons, 4.4.2.2of ENV 1992-1-1applies, except for rule (8): unbonded prestressing tendons should not be taken intoaccount as minimum reinforcement.




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4.4.2.3 Control of cracking without direct calculation

4.4.2.4 Calculation of crack width

5 Detailing provisions

This clause of ENV 1992-1-1 is applicable except an follows:

5.3 Prestressing units5.3.1 Arrangement of the prestressing units

5.3.2 Concrete cover

Addition after Application Rule (6):P(107) Where all tendons are external or internal and unbonded, the rules specific to prestressedconcrete given in 4.4.2.3of ENV 1992-1-1, do not apply.

Replacement of Application Rule (4) by:(104) Application Rule (4) in 4.4.2.4of ENV 1992-1-1 does not apply to unbonded tendons.

Replacement of principal P(1), P(2) and Application Rule (3) by:P(101) External tendons shall be adequately protected against physical attack or vandalism.P(102) Where specified by the contract, replacement of the tendons shall be provided for.

(103) For external tendons, replaceability is normally required by the approval documents ofthe system.

(104) For internal tendons, the conditions to be met for the replacement and the number oftendons which may be simultaneously replaced should be specified in each particularcase.

P(105) Critical transverse vibrations of the external tendons due to traffic, wind or any other cause

shall be avoided by means of appropriate devices.P(106) In aggressive environment, i.e. exposure class 3, 4 or 5 in ENV 1992-1-1, Table 4.1, the contact

between continuous prefabricated segments shall be ensured by a thin layer of epoxy resin orother appropriate material.(107) The deviators should be detailed to allow for an angular inaccuracy of arbitrary direction

at least |0.02| rad at both their ends.(108) In the absence of indication in the approval documents of the system, the minimum

radius of curvature of monostrands should comply with the following values:monostrands 13 mm: 1.7 mmonostrands 15 mm: 2.5 m

(109) In the absence of indication in the approval documents of the system, the tendons should

exit the anchorages with a minimum straight length of the following values:Tendons up to 2 MNultimate strength: 0.8 mTendons between 2 MNand 6 MNultimate strength: 1.0 mTendons with more than 6 MNultimate strength: 1.5 m

(110) Bundling of unbonded internal tendons is permitted in areas outside the anchorage zonesprovided that placing and compacting of the concrete can be carried out satisfactorily.

Replacement of Principle P(1):P(101) The rules of minimum concrete cover given in clause 5.3.2of ENV 1992-1-1 do not apply to

unbonded internal tendons.

(102) The concrete cover on unbonded internal tendons should not be less than |20| mm




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5.5 Limitation of damage due to accidental action

5.5.2 Proportioning of ties

6 Construction and workmanship

This clause of ENV 1992-1-1 applies as far as it is deemed appropriate in each case.7 Quality control

This clause of ENV 1992-1-1 applies as far as it is deemed appropriate in each case.

Addition after Application Rule (4):P(105) Structures prestressed by continuous unbonded tendons may be more sensitive to progressive

collapse since a local defect may have consequences at remote parts.P(106) If unbonded tendons are part of the tying system of the structure it shall be checked that a

redistribution of forces is possible in case of local failure of a tendon. This may be obtained by anappropriate bonded reinforcement.(107) Continuous slabs should be checked to ensure that simultaneous failure of any two

adjacent unbonded tendons will not cause collapse.




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Appendix 1 Additional provisions for the determination of the effects oftime-dependent deformation of concrete


Appendix 2 Non-linear analysis

This clause of ENV 1992-1-1 applies as far as it is deemed appropriate in each case except as follows:

Appendix 3 Supplementary information on the ultimate limit states induced bystructural deformation


Appendix 4 Checking deflections by calculation


Addition after Principle P(4):(105) In segmental construction with open joints at the ultimate limit states, non-linear

methods of analysis should be used.(106) At the ultimate limit states, the increase of stresses in the tendons should be calculated

using non-linear methods of analysis and taking account of tension-stiffening effects.




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