Un i t e dKi n g d o mo fGr e a t Br i t a i na n dNo r t h e r nI r e l a n d ≠ EDI CTOFGOVERNMENT± I no r d e rt op r o mo t ep u b l i ce d u c a t i o na n dp u b l i cs a f e t y ,e q u a lj u s t i c ef o r a l l ,ab e t t e ri n f o r me dc i t i z e n r y ,t h er u l eo fl a w,wo r l dt r a d ea n dwo r l d p e a c e ,t h i sl e g a ld o c u me n ti sh e r e b yma d ea v a i l a b l eo nan o n c o mme r c i a l b a s i s ,a si ti st h er i g h to fa l lh u ma n st ok n o wa n ds p e a kt h el a wst h a t g o v e r nt h e m BS NA EN 1998-2 (2005) (English): UK National Annex to Eurocode Design of structures for earthquake resistance Bridges Nu l l iv e n d e mu s ,n u l l in e g a b i mu sa u td i f f e r e mu sRe c t u ma u tJu s t i c i a m Wewi l ls e l lt on oma n ,wewi l ln o td e n yo rd e f e rt oa n yma ne i t h e rJu s t i c eo rRi g h t MAGNACARTA( 97 ) NA to BS EN 1998-2:2005 UK National Annex to Eurocode 8: Design of structures for earthquake resistance Part 2: Bridges NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW raising standards worldwide™ NA to BS EN 1998-2:2005 NATIONAL ANNEX Publishing and copyright information The BSI copyright notice displayed in this document indicates when the document was last issued © BSI 2009 ISBN 978058055091 ICS 91.120.25; 93.040 The following BSI references relate to the work on this standard: Comm ittee reference B/525/8 Draft for comment 08/30129892 DC Publication history First published June 2009 Amendments issued since publication Date Text affected NA to BS EN 1998-2:2005 NATIONAL ANNEX Contents Introduction NA.1 Scope NA.2 Nationally Determined Parameters NA.3 Decisions on the status of informative annexes NA.4 References to non-contradictory complementary information Bibliography List of tables Table NA.1 - UK values for Nationally Determined Parameters described in BS EN 1998-2:2005 Summary of pages This document comprises a front cover, an inside "front cover, pages i to ii, pages to 10, an inside back cover and a back cover â BSI 2009 ã NA to BS EN 1998-2:2005 ii ã â BSI 2009 NATIONAL ANNEX This page deliberately left blank NA to BS EN 1998-2:2005 NATIONAL ANNEX National Annex (informative) to BS EN 1998-2:2005, Eurocode 8: Design of structures for earthquake resistance Part 2: Bridges Introduction This National Annex has been prepared by BSI Subcommittee B/525/8, Structures in seismic regions In the UK it is to be used in conjunction with BS EN 1998-2:2005 NA.1 Scope This National Annex gives: a) the UK decisions for the l\Iationally Determined Parameters described in the following subclauses of BS EN 1998-2:2005: 2.1(3)P 5.6.2(2)P b 2.1 (4)P 5.6.3.3(1)P b 2.1 (6) 6.2.1.4(1)P 2.2.2(5) 6.5.1(1)P 2.3.5.3(1) 6.6.2.3(3) 2.3.6.3(5) 6.6.3.2(1)P 2.3.7(1) 6.7.3(7) 3.2.2.3 7.4.1(1)P 3.3{1 )P 7.6.2(1)P 3.3(6) 7.6.2(5) 4.1.2(4)P 7.7.1 (2) 4.1.8(2) J.1 (2) 5.3(4) J.2{1 ) 5.4{1 ) NA.2 b) the UK decisions on the status of BS EN 1998-2:2005 informative annexes; and c) references to non-contradictory complementary information Nationally Determined Parameters UK decisions for the Nationally Determined Parameters described in BS EN 1998-2:2005 are given in Table NA.1, © BSI 2009 • z N Table NA.1 @ Subclause Nationally Determined Parameter Eurocode recommendation UK decision o 2.1 (3)P Reference retu rn period TNCR of seismic action for the no-collapse requirement (or, equivalently, reference probability of exceedance in 50 years, PNCR) TNCR = 475 years In the absence of a project-specific assessment, adopt a return period TNCR of 500 years Further guidance is given in PD 6698 OJ OJ ~ N 0 \.0 2.1 (4)P UK values for Nationally Determined Parameters described in BS EN 1998-2:2005 Importance classes for bridges PNCR = 10% » r-+ ~ m Z \ \ 00 I In general road and railway bridges are considered to belong to importance class II (average importance) Importance class III comprises bridges of critical importance for maintaining communications, especially in the immediate post-earthquake period, bridges where failure is associated with a large number of probable fatalities, and major bridges where a design life greater than normal is required The importance classes should be established on a project-specific basis Further guidance is given in PD 6698 rv rv o o U'1 A bridge may be classified as importance class I (less than average importance) when both the following conditions are met: the bridge is not critical for communications, and the adoption of either the reference probability of exceedance, PNCR, in 50 years for the design seismic action, or of the standard bridge design life of 50 years is not economically justified Importance classes I, II and III correspond roughly to consequences classes CC1, CC2 and CC3, respectively, defined in BS EN 1990:2002, B3.1 2.1 (6) Importance factors for bridges For importance class I, YI = 0,85 For importance class III, YI = 1,3 2.2.2(5) 2.3.5.3(1) Where a value for the reference return period TNCR of 500 years has been adopted for CC3 bridges, YI=1 may be assumed Where TNCR has been assessed on a project-specific basis, YI should also be chosen on a project-specific basis Further guidance is given in PD 6698 Conditions under which the seismic action may be considered as an accidental action, and the requirements of 2.2.2(3) and 2.2.2(4) may be relaxed 2.2.2(3) and 2.2.2(4) should apply when the reference period TNCR is approximately equal to 475 years In the absence of project-specific requirements, the requirements of 2.2.2(3) and 2.2.2(4) may be relaxed Further guidance is given in PD 6698 Expression for the length of plastic hinges Use the expression in Annex E Expression E.19 in Annex E may be adopted, or other appropriate values may be used z ~ oz »r »z Z m >< Table NA.1 z UK values for Nationally Determined Parameters described in BS EN 1998-2:2005 (continued) ~ Subclause Nationally Determined Parameter Eurocode recommendation UK decision 2.3.6.3(5) PE and PT, fractions of design seismic and thermal displacements for checking non-critical structural elements PE = 0.4 (for the design seismic displacement) Use recommended values 2.3.7(1) Note I Selection of categories of bridge, ground type and seismic zone for which the provisions for low seismicity apply o z » r» z PT = 0.5 (for the thermal movement) Z The recommended definition of low seismicity is given in the Note to BS EN 1998-1 :2004, 3.2.1 (4) All categories of bridge, ground type and seismic zone may be designed using the provisions for low seismicity 2.3.7(1) Note Simplified criteria for the design of bridges in cases of low seismicity The simple criteria should be based on a limited ductility/essentially elastic seismic behaviour of the bridge, for which no special ductility requirements are necessary Further guidance is given in PD 6698 3.2.2.3(1)P Definition of active fault A seismotectonic fault may be considered active when there is an average historic slip rate of at least mm/year and topographic evidence of seismic activity within the Holocene times (past 11 000 years) For the purposes of this requirement, all faults may be considered as not active Further guidance is given in PD 6698 3.3(1)P Length of continuous deck Llim beyond which the spatial variability of seismic action might have to be taken into account where soil properties along the bridge are approximately uniform Lg/1,5 where Lg is defined in Table 3.1 N, which is contained in Note to 3.3(6) and is reproduced in the row below m X is given in the table below - Ground type IA See Note IB See Note Ie ID 333 200 See Note IE 1 z » , p @ NOTE Spatial variability of ground motions need not be considered for bridges with continuous decks, where the supports are founded on approximately uniform soils of type A, B or C O::l !:!! N o o w Further guidance is given in PD 6698 o to V\ m Z ~ U) U) (X) I I\J I\J o o U1 ~ Table NA.1 @ Subclause Nationally Determined Parameter Eurocode recommendation UK decision 3.3(6) Note Distance Lg beyond which the seismic ground motions can be considered as completely u ncorrelated Table 3.1 N: Distance Lg beyond which ground motions may be considered uncorrelated Use recommended values OJ ~ N UK values for Nationally Determined Parameters described in BS EN 1998-2:2005 (continued) o o 3.3(6) Note Factor f3r used in calculating differential displacements between piers Ground type IA IB IC Lg(m) I 600 I 500 I 400 I 300 I 500 r-+ o OJ Vl m Z \ \ I DIE f3r = 0,5 when the ground type is the same z » 00 I I\ J I\ J o o V1 Use recommended values for the three piers f3r = 1,0 when the ground type of one of the three piers is different 4.1.2(4)P = 0,2 = 0,3 l/12,1 values for traffic loads assumed concurrent with the design seismic action For road bridges l/12,1 4.1.8(2) Upper limit for the value in the left-hand-side of expression 4.4 for the seismic behaviour of a bridge to be considered irregular Po 5.3(4) Value of overstrength factor Yo For concrete members Yo For rail bridges l/12,1 =2 Use recommended value For steel members Yo 5.4(1) Simplified methods for second order effects in linear analysis In the absence of project-specific requirements, the recommended values may be adopted = 1,35 Use recommended values = 1,25 Assume the increase of bending moments fJ.M of the plastic hinge section due to second order effects is: Use recommended values Further guidance is given in PD 6698 1+q ~M = dEdNEd z ~ where NEd is the axial force and d Ed is the relative transverse displacement of the ends of the considered ductile member, both in the design seismic situation 5.6.2(2)P b Value of additional safety factor YBd1 on shear resistance YBd1 = 1,25 I Use recommended value oz » r » z Z m >< Table NA.1 UK values for Nationally Determined Parameters described in BS EN 1998-2:2005 (continued) Subclause Nationally Determined Parameter Eurocode recommendation UK decision S.6.3.3(1}P b Choice of alternative methods of calculating YBd Alternative is more conservative Either method may be used 6.2.1.4(1}P Type of confinement reinforcement All types are acceptable All types are acceptable, provided limited ductility or elastic behaviour is achieved 6.S.1(1}P Simplified verification rules for bridges of limited ductile behaviour in low seismicity cases In areas of low seismicity, the same verification rules should apply to the design of structures of limited ductile behaviour as those applicable in areas of moderate or high seismicity Use the recommended procedure (i.e the provisions of BS 1998-2:2005, 6.5, should be observed in bridges designed for limited ductile behaviour) 6.6.2.3(3} Allowable extent of damage of elastomeric bearings in bridges where the seismic action is considered as accidental action, but is not resisted entirely by elastomeric bearings [None] In the absence of a project-specific requirement, the extent of damage should be limited to enable the bearings to sustain Load Models and loading in accordance with BS EN 1991-2:2003 Further guidance is given in PD 6698 6.6.3.2(1}P Percentage PH of the compressive (downward) reaction due to the permanent load that is exceeded by the total vertical reaction on a support due to the design seismic action for holding-down devices to be required PH = 80% in bridges of ductile behaviour, where the vertical reaction due to the design seismic action is determined as a capacity design effect PH 50% in bridges of limited ductile behaviour, where the vertical reaction due to the design seismic action is determined from the analysis under the design seismic action alone (including the contribution of the vertical seismic component) z ~ oz » r » z Z m X Use recommended values z » 1"'+ o OJ V\ m @ t:IJ VI N o o ~ • V1 Z 1 00 I N N o o U1 m • @ OJ ~ Table NA.1 z UK values for Nationally Determined Parameters described in BS EN 1998-2:2005 (continued) » M- o Subclause Nationally Determined Parameter Eurocode recommendation UK decision 6.7.3{7} Upper value of design seismic displacement d lim for monolithic connection of abutment to the deck to limit damage of the soil or embankment behind the abutments Recommended limit value of design seismic displacement at abutments rigidly connected to the deck In the absence of project-specific requirements, use the recommended values IV o o 1.0 7.4.1 (1}P Value of control period TD for the design spectrum of bridges with seismic isolation Bridge importance class Displacement limit d lim {mm} III 30 II 60 I No limitation A value of TD greater than that specified in BS EN 1998-1 :2004, 3.2.2.5.8{P), may be specified OJ Vl m \.0Z \.0 00 I rv rv o o U1 In the absence of a project-specific requirement, a value of TD greater than the period of the fundamental mode of vibration of the bridge T should be adopted Further guidance is given in PD 6698 7.6.2{1}P Value of amplification factor YIS on design displacement of isolator units YIS = 1,5 Use recommended value 7.6.2{5} Value of Ym for elastomeric bearings Ym = 1,15 Ym = 1,0 7.7.1{2} Ow and Dd, numerical coefficients Ow expressing appropriate fractions of Wd and da,max respectively Dd J.1 {2} Tmin,b, minimum design temperature for determining upper and lower bound design properties of the isolator , 0,015 = 0,5 Tmin,b =1/J2 Tmin + Ll T1 In the absence of a project-specific requirement, use the recommended values Further guidance is given in PD 6698 Tmin,b = Tave - 1/J2 {Tave Tmin} + LlT1 where: where: Tmin is the value of the minimum shade air temperature at the bridge location having an annual probability of (negative) exceedance of 0,02, in accordance with BS EN 1991-1-5:2003, 6.1.3.2 Tave is the average shade air temperature at the bridge location throughout the year In the absence of more precise data, Tave may be taken as Tave = (Tmin + Tmax}/2 z ~ oz » r» z Z m X Table NA.1 Subclause z UK values for Nationally Determined Parameters described in BS EN 1998-2:2005 (continued) Nationally Determined Parameter J.1 (2) (continued) ~ Eurocode recommendation UK decision 1/J2 =0,50 is the combination factor for thermal actions for seismic design situation, in accordance with BS EN 1990:2002, Annex A2 is the shade air temperature at the bridge location with an annual probability of 0,0083 (120 year return) that a lower temperature is recorded, in accordance with BS EN 1991-1-5:2003, 6.1.3.2, adjusted by Annex A and its National Annex (Note that a different annual probability may be specified for an individual project.) L1T1 takes the following values depending on the material of the bridge deck, in accordance with BS EN 1991-1-5:2003, Figure 6." Value of IlT1 for the determination of minimum isolator temperature Deck Concrete Composite 7,5 5,0 Steel (OC) oz » r» z Z m >< Tmax is the corresponding shade air temperature at the bridge location with an annual probability of 0,0083 (120 year return) that a higher temperature is recorded 1/J2 = 0,50 is the combination factor for thermal actions for seismic design situation, in accordance with BS EN 1990:2002, Annex A2 L1 T1 takes the following values depending on the bridge deck type, as defined in BS EN 1991-1-5:2003,6.1.1 Value of IlT1 for the determination of minimum isolator temperature Deck Concrete Composite Steel L1T1 (OC) 7,5 5,0 -2,5 Further guidance is given in PD 6698 J.2{1 ) @ OJ !:!! N Values of A-factors for commonly used isolators Use values and guidance in Annex JJ Values of A-factors should be determined by tests on prototype isolators, particularly in the case of elastomeric isolators z » -+ o OJ VI m Z .a 1 o o (X) • o o "-J I I'.J I'.J V1 NA to BS EN 1998-2:2005 NA.3 NATIONAL ANNEX Decisions on the status of informative annexes BS EN 1998-2:2005 informative Annex A: Probabilities related to the reference seismic action Guidance for the selection of design action during the construction phase is not appropriate for use in the UK as an informative annex See also PD 6698 BS EN 1998-2:2005 informative Annex B: Relationship between displacement ductility and curvature ductility factors of plastic hinges in concrete piers may be used in the UK as an informative annex See also PD 6698 BS EN 1998-2:2005 informative Annex C: Estimation of the effective stiffness of reinforced concrete ductile members may be used in the UK as an informative annex See also PD 6698 BS EN 1998-2:2005 informative Annex D: Spatial variability of earthquake ground motion: model and methods of analysis may be used in the UK as an informative annex See also PD 6698 BS EN 1998-2:2005 informative Annex E: Probable material properties and plastic hinge deformation capacities for non-linear analyses may be used in the UK as an informative annex BS EN 1998-2:2005 informative Annex F: Added mass of entrained water for immersed piers may be used in the UK as an informative annex BS EN 1998-2:2005 informative Annex H: Static non-linear analysis (pushover) may be used in the UK as an informative annex BS EN 1998-2:2005 informative Annex JJ: A-factors for common isolator types may be used in the UK as an informative annex BS EN 1998-2:2005 informative Annex K: Tests for validation of design properties of seismic isolator units may be used in the UK as an informative annex pending the publication of BS EN 15129 NA.4 References to non-contradictory complementary information The following is a list of references that contain non-contradictory complementary information for use with BS EN 1998-2 ã ã â BSI 2009 PD 6698:2008, Recommendations for the design of structures for earthquake resistance to BS EN 1998 NA to 85 EN 1998-2:2005 NATIONAL ANNEX Bibliography Standards publications For dated references, only the edition cited applies For undated references, the latest edition of the referenced document (including any amendments) applies BS EN 1990:2002, Eurocode - Basis of structural design BS EN 1991-1-5:2003, Eurocode 1: Actions on structures - Part 1-5: General actions - Thermal actions BS EN 1991-2:2003, Eurocode 1: Actions on structures - Part 2: Traffic loads on bridges â B512009 ã NA to BS EN 1998-2:2005 This page deliberately left blank NATIONAL ANNEX British Standards Institution (BSI) BSI is the independent national body responsible for preparing British Standards and other standards-related publications, information and services It presents the UK view 'On standards in Europe and at the international level BSI is incorporated by Royal Charter British Standards and other standardisation products are published by BSI Standards Limited Revisions Information on standards British Standards and PASs are periodically updated by amendment or revision Users of British Standards and PASs should make sure that they possess the latest amendments or editions BSI provides a wide range of information on national, European and international standards through its Knowledge Centre It is the constant aim of BSI to improve the quality of our products and services We would be grateful if anyone finding an inaccuracy or ambiguity while using British Standards would inform the Secretary of the technical committee responsible, the identity of which can be found on the inside front cover.Similary for PASs, please notify BS I Customer Services Tel: +44 (0)20 8996 7004 Fax: +44 (0)20 8996 7005 Email: knowledgecentre@bsigroup.com Tel: +44 (0)20 8996 9001 Fax: +44 (0)20 8996 7001 BSI Subscribing Members are kept up to date with standards developments and receive substantia l discounts on the purchase price of standards For details of these and other benefits contact Membership Administration BSI offers BSI Subscribing Members an individual updating service called PLUS which ensures that subscribers automatically receive the latest editions of British Standards and PASs Tel: +44 (0)20 8996 7002 Fax: +44 (0)20 8996 7001 Email: membership@bsigroup.com Tel: +44 (0)20 8996 7669 Fax: +44 (0)20 8996 7001 Email: plus@bsigroup.com Information regarding online access to British Standards and PASs via British Standards Online can be found at www.bsigroup.com/BSOL Buying standards Further information about British Standards is available on the BSI website at www.bsi-group.com/standards You may buy PDF and hard copy versions of standards directly using a credit card from the BSI Shop on the website www.bsigroup.com/shop In addition all orders for BSI, international and foreign standards publications can be addressed to BSI Customer Services Tel: +44 (0)20 8996 9001 Fax: +44 (0)20 8996 7001 Email: orders@bsigroup.com In response to orders for international standards, BSI will supply the British Standard implementation of the relevant international standard, unless otherwise requested Copyright All the data, software and documentation set out in all British Standards and other BSI publications are the property of and copyrighted by BSI, or some person or entity that own copyright in the information used (such as the international standardisation bodies) has formally licensed such information to BSI for commerical publication and use Except as permitted under the Copyright, Designs and Patents Act 1988 no extract may be reproduced, stored in a retrieval system or transmitted in any form or by any means - 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