Eurocode 1 - Basis of design and actions on structures Part 2.5 : Thermal actions

Transcription

1 EUROPEAN PRESTANDARD PRÉNORME EUROPÉENNE EUROPÄISCHE VORNORM ENV March 1997 English version Eurocode 1 - Basis of design and actions on structures Part 2.5 : Thermal actions Eurocode 1 - Bases de calcul et actions sur les structures - Partie 2-5 : Eurocode 1 - Grundlagen der Tragwerksplanung und Einwirkungen auf Tragwerke - Teil 2-5 : CEN European Committee for Standardization Comité Européen de Normalisation Europäisches Komitee für Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels CEN 1997 Copyright reserved to all CEN members Ref.No

2 Page 2 ENV :1997 Contents Page Foreword 3 Objectives of the Eurocodes 4 Background to the Eurocode Programme 4 Eurocode Programme 4 National Application Documents (NAD's) 5 Matters Specific to this Prestandard 5 1 General Scope Scope of ENV 1991-Eurocode Scope of ENV Thermal Actions Further Parts of ENV Normative references Distinction between principles and application rules Definitions Symbols 10 2 Classification of actions 13 3 Design situations 14 4 Representation of actions 15 5 Temperature changes in buildings General Building structures Cladding elements Determination of temperature profiles 18 6 Temperature changes in bridges Bridge decks Bridge deck groupings Treatment of thermal actions Uniform temperature component - characteristic values Linear temperature component - characteristic values Co-existence of uniform and linear temperature components Differences in effective temperature between different structural 24 elements 6.2 Bridge piers Treatment of thermal actions Temperature differences - characteristic value 24

3 Page 3 7 Temperature changes in industrial chimneys and pipelines General Temperature components - characteristic values Shade air temperature Solar radiation Flue gas temperature Effective element temperature Thermal actions to be considered Determination of temperature components Characteristic values of temperature components (indicative values) Combination of actions 27 Annex A Isotherms of national minimum and maximum shade air temperatures (Informative) 29 Annex B Models for the assessment of non-linear thermal actions in bridges (Normative) 48 Annex C Determination of temperature effects in bridge decks (Informative) 52 Annex D Coefficients of linear expansion (Informative) 58

4 Page 4 Foreword Objectives of the Eurocodes (1) The "Structural Eurocodes" comprise a group of standard for the structural and geotechnical design of buildings and civil engineering works. (2) They cover execution and control only to the extent that is necessary to indicate the quality of the construction products, and the standard of the workmanship, needed to comply with the assumptions of the design rules. (3) Until the necessary set of harmonized technical specification for products and for methods of testing their performance are available, some of the Structural Eurocodes cover some of these aspects in informative Annexes. Background to the Eurocode Programme (4) The Commission of the European Communities (CEC) initiated the work of establishing a set of harmonized technical rules for the design of building and civil engineering works which would initially serve as an alternative to the different rules in force in the various Member States and would ultimately replace them. These technical rules became known as the "Structural Eurocodes". (5) In 1990, after consulting their respective Member States, the CEC transferred the work of further development, issue and updating of the Structural Eurocodes to CEN, and the EFTA Secretariat agreed to support the CEN work. (6) CEN Technical Committee CEN/TC 250 is responsible for all Structural Eurocodes. Eurocode Programme (7) Work is in hand on the following Structural Eurocodes, each generally consisting of a number of parts: EN 1991 Eurocode 1 Basis of design and actions on structures EN 1992 Eurocode 2 Design of concrete structures EN 1993 Eurocode 3 Design of steel structures EN 1994 Eurocode 4 Design of composite steel and concrete structures EN 1995 Eurocode 5 Design of timber structures EN 1996 Eurocode 6 Design of masonry structures EN 1997 Eurocode 7 Geotechnical design EN 1998 Eurocode 8 Design of structures for earthquake resistance EN 1999 Eurocode 9 Design of aluminium alloy structures (8) Separate sub-committees have been formed by CEN/TC250 for the various Eurocodes listed above.

5 Page 5 (9) This part of Eurocode 1 is being published by CEN as a European Prestandard (ENV) with an initial life of three years. (10) This Prestandard is intended for experimental application and for the submission of comments. (11) After approximately two years CEN members will be invited to submit formal comments to be taken into account in determining future actions. (12) Meanwhile feedback and comments on this Prestandard should be sent to the Secretariat of CEN/TC250/SC1 at the following address: SIS/BST Box S Stockholm SWEDEN or to your national standards organisation. National Application Documents (NADs) (13) In view of the responsibilities of authorities in member countries for safety, health and other matters covered by the essential requirements of the Construction Products Directive (CPD), certain safety elements in this ENV have been assigned indicative values which are identified by or [ ] ( boxed values ). The authorities in each member country are expected to review the boxed values and may substitute alternative definitive values for these safety elements for use in national application. (14) Some of the supporting European or International standards may not be available by the time this Prestandard is issued. It is therefore anticipated that a National Application Document (NAD) giving any substitute definitive values for safety elements, referencing compatible supporting standards and providing guidance on the national application of this Prestandard, will be issued by each member country or its Standards Organisation. (15) It is intended that this Prestandard is used in conjunction with the NAD valid in the country where the building or civil engineering works is located. Matters Specific to this Prestandard (16) The scope of Eurocode 1 is defined in and the scope of this Part of Eurocode 1 is defined in Additional parts of Eurocode 1 which are planned are indicated in (17) This Part is complemented by a number of annexes, some normative and some informative. The normative annexes have the same status as the sections to which they relate. (18) The characteristic value of isotherms of National minimum and maximum shade air temperatures shall be provided in the form of maps or otherwise (see Annex A) by the competent authority. The value provided for characteristic loads shall conform with the definitions given in ENV Clause 4.2.

6 Page 6 (19) Allowance shall be made in the NAD for local effects which are unlikely to have been considered in the statistical analysis for national loads. (20) Where there is doubt about the validity of the recommended minimum and maximum shade air temperatures, the procedure to consult the competent authority should be given in the NAD.

7 Page 7 Section 1 General 1.1 Scope Scope of ENV 1991 Eurocode 1 (1)P ENV 1991 provides general principles and actions for the structural design of buildings and civil engineering works including some geotechnical aspects and shall be used in conjunction with ENV (2) It may also be used as a basis for the design of structures not covered in ENV and where other materials or other structural design actions are involved. (3) ENV 1991 also covers structural design during execution and structural design for temporary structures. It relates to all circumstances in which a structure is required to give adequate performance. (4) ENV 1991 is not directly intended for the structural appraisal of existing construction, in developing the design of repairs and alterations or, for assessing changes of use. (5) ENV 1991 does not completely cover special design situations which require unusual reliability considerations such as nuclear structures for which specific design procedures should be used Scope of ENV Thermal Actions (1)P This Part gives rules and methods of calculating thermal actions on buildings, bridges and other structures including their structural components. Principles needed for cladding and other appendages of the buildings are also provided. (2) This Part of the Eurocode on Actions on Structures describes the changes in the temperature of structural elements. Characteristic values of thermal actions are presented for use in the design of structures which are exposed to daily and seasonal climatic changes. (3) Structures in which thermal actions are mainly a function of their use (e.g. chimneys, cooling towers, silos, tanks, warm and cold storage facilities, hot and cold services) are treated in section 7. (4) The following subjects are dealt with: Section 1 - General Section 2 - Classification of actions Section 3 - Design situations Section 4 - Representation of actions Section 5 - Temperature changes in buildings Section 6 - Temperature changes in bridges Section 7 - Temperature differences in industrial chimneys and pipelines

8 Page Further Parts of ENV 1991 (1) Further Parts of ENV 1991 which, at present, are being prepared or are planned are given in Normative references This European Prestandard incorporates by dated or undated reference, provisions from other standards. These normative references are cited at the appropriate places in the text and publications listed hereafter. ISO Basis of design for structures Notations. General symbols NOTE: The following European Prestandards which are published or in preparation are cited at the appropriate places in the text and publications listed hereafter. ENV ENV ENV ENV ENV ENV ENV ENV ENV ENV ENV 1992 ENV 1993 ENV 1994 ENV 1995 ENV 1996 ENV 1997 Eurocode 1: Basis of design and actions on structures Part 1 : Basis of design Eurocode 1: Basis of design and actions on structures Part 2.1 Densities, self-weight, imposed loads Eurocode 1: Basis of design and actions on structures Part 2.2 Actions on structures exposed to fire Eurocode 1: Basis of design and actions on structures Part 2.3: Snow loads Eurocode 1: Basis of design and actions on structures Part 2.4: Wind actions Eurocode 1: Basis of design and actions on structures Part 2.6: Actions during execution Eurocode 1: Basis of design and actions on structures Part 2.7: Accidental actions due to impact and explosions Eurocode 1: Basis of design and actions on structures Part 3: Traffic loads on bridges Eurocode 1: Basis of design and actions on structures Part 4: Actions in silos and tanks Eurocode 1: Basis of design and actions on structures Part 5: Actions induced by cranes and machinery Eurocode 2: Design of concrete structures Eurocode 3: Design of steel structures Eurocode 4: Design of composite steel and concrete structures Eurocode 5: Design of timber structures Eurocode 6: Design of masonry structures Eurocode 7: Geotechnical design

9 ENV 1998 Eurocode 8: Earthquake resistant design of structures ENV 1999 Eurocode 9: Design of aluminium alloy structures 1.3 Distinction between principles and application rules Page 9 (1) Depending on the character of the individual clauses, distinction is made in this Part 2-5 of ENV 1991 between principles and application rules. (2) The principles comprise: general statements and definitions for which there is no alternative, as well as; requirements and analytical models for which no alternative is permitted unless specifically stated. (3) The principles are identified by the letter P following the paragraph number. (4) The application rules are generally recognised rules which follow the principles and satisfy their requirements. (5) It is permissible to use alternative rules different from the application rules given in this Eurocode, provided it is shown that the alternative rules accord with the relevant principles and have at least the same reliability. (6) In this Part of ENV 1991 the application rules are identified by a number in brackets e.g. as this clause.

10 Page Definitions For the purposes of this prestandard, a basic list of definitions is provided in ENV , and the additional definitions given below are specific to this Part Thermal actions: Thermal actions on a structure or a structural element are the ranges of temperature fields within a specified time interval Shade air temperature: The shade air temperature is the temperature measured by thermometers placed in a white painted louvred wooden box known as a Stevenson screen. The object of the screen is to shield the thermometers from (i) radiation by day from the sun, the ground or neighbouring objects, (ii) loss of heat by radiation at night, and (iii) precipitation, while at the same time allowing free passage of air. This is achieved by the use of louvres in the sides and door, a double roof with an air space and a floor consisting of three partially overlapping boards separated by an air space. The screen in mounted on a stand so that the thermometer bulbs are about 1,20 m above the ground, which can be taken as level, covered with short grass and well away from trees, buildings, walls or other obstructions. The dry bulb thermometer gives the air temperature at the time of observation and the maximum and minimum thermometers are read once or more daily, according to the type of station, and set immediately after they are read Maximum shade air temperature T max : annual value of maximum shade air temperature with return period 50 years, based on the maximum hourly values recorded Minimum shade air temperature T min : annual value of minimum shade air temperature with return period 50 years, based on the minimum hourly values recorded. 1.5 Symbols (1) For the purposes of this Part of Eurocode 1, the following symbols apply. NOTE: The notation used is based on ISO 3898:1987 (2) A basic list of notations is provided in ENV , and the additional notations below are specific to this Part. Latin upper case letters T max annual value of maximum shade air temperature with return period 50 years, based on the maximum hourly values recorded T min annual value of minimum shade air temperature with return period 50 years, based on the minimum hourly values recorded R return period of maximum (minimum) shade air temperature [years] T max,r annual value of maximum shade air temperature with return period R T min,r annual value of minimum shade air temperature with return period R T e.max maximum effective bridge temperature minimum effective bridge temperature T e.min

11 Page 11 T 0 datum effective structural element temperature when is restrained T 1,T 2, T 3,T 4 T K T 1 ' T 1 T 2 T N,pos T N,neg T N T M,pos T M,neg T E o C A E J B H values of positive (negative) temperature difference profile characteristic value of thermal action infrequent value of thermal action frequent value of thermal action quasi-permanent value of thermal action maximum range of positive effective bridge temperature maximum range of negative effective bridge temperature overall range of effective bridge temperature positive linear temperature differences negative linear temperature differences non-linear part of the temperature differences degree used for temperature values e.g. shade air temperature, datum temperature, effective bridge temperature, temperature differences area of the cross-section Young s modulus of elasticity moment of inertia width of the cross-section height of the cross-section Latin lower case letters d wall thickness of the chimney or pipeline u, c location and scale parameters of annual maximum (minimum) shade air temperature distribution k 1, k 2 coefficients for calculation of maximum (minimum) shade air k 3, k 4 temperature with return period other than 50 years surfacing factor for linear temperature differences k sur Greek lower case letters α T coefficient of linear expansion (1/ C) ω N reduction factor of uniform temperature component for combination with linear temperature differences ω M reduction factor of linear temperature differences for combination with uniform temperature component

12 Page 12 ψ 0 ψ 1 ' ψ 1 ψ 2 Coefficient for combination value of thermal action Coefficient for infrequent value of thermal action Coefficient for frequent value of thermal action Coefficient for quasi-permanent value of thermal action

13 Page 13 Section 2 Classification of actions (1)P Thermal actions are classified as variable, free actions, see ENV (2)P Thermal actions are indirect actions, see ENV (3) Characteristic values of thermal actions as given in this Part are 50 years return values, unless stated otherwise.

14 Page 14 Section 3 Design situations (1)P The relevant thermal actions shall be determined for each design situation identified in accordance with ENV and ENV (2)P The temperature distribution within a cross-section of any element leads to deformation of the element. When the deformation is restrained, stresses occur in the element. These stresses shall be considered for both persistent and transient design situations (e.g. during execution or repair) according to ENV (3)P The elements of the loadbearing structure shall be checked to ensure that thermal movement will not cause overstressing of the structure, either by the provision of expansion joints or by including the effects in the design. (4) In special cases accidental design situations should be considered, see section 7.1.

15 Page 15 Section 4 Representation of actions (1)P Daily and seasonal changes in shade air temperature, solar radiation, re-radiation, etc., will result in variations of the temperature distribution within individual elements of a structure. (2)P The magnitude of the thermal effects will be dependent on local climatic conditions, together with the orientation of the structure, its overall mass, finishes (e.g. cladding in buildings), and in the case of building structures, heating and ventilation regimes and thermal insulation. (3) The temperature distribution within an individual structural element may be split into the following four essential constituent components, as illustrated in figure 4.1: a) A uniform temperature component, T N; b) A linearly varying temperature component about the z-z axis, T MZ; c) A linearly varying temperature component about the y-y axis, T MY; d) A non-linear temperature distribution, T E. This results in a system of selfequilibrated stresses which produce no net load effect on the element. y y z z x Center of gravity (a) (b) (c) (d) Τ MY Figure 4.1: Constituent components of a temperature profile (4)P The strains and therefore any resulting stresses, are dependent on the geometry and boundary conditions of the element being considered and on the physical properties of the material used. When materials with different coefficients of linear expansion are used compositely see annex C5.

16 Page 16 Section 5 Temperature changes in buildings 5.1 General (1)P This Section deals with the effects of thermal actions on building structures and cladding where the temperature within the envelope normally varies by less than 20 o C during normal use. (2)P This section only deals with thermal actions arising from climatic effects due to the variation of shade air temperature and solar radiation. The possible effects of shading by adjacent buildings should be taken account in the design. Thermal actions arising from internal unfavourable heating, effects of plant or industrial processes shall be covered in the project specification. (3) The allowances required in assessing the behaviour of the structure and its cladding are dependent on the type of structure, the cladding employed and the expected internal and external temperature history. Accordingly specific rules cannot be provided. (4) The following rules are a guide to the matters which should be considered in the design; appropriate detailed assessments for each structure should be considered in the design. (5) To define the effects of thermal actions on buildings, three definitions are required: building envelope; the part of structure providing either or both the weather resistant membrane or the structural skin to the building; cladding: the part of the building not carrying load other than self weight or wind which provides a weatherproof membrane; load bearing structure: those elements which carry the actions applied to the building; permanent finishes and internal structural walls are included. (6)P The effects of thermal actions shall be considered where there is a possibility of the ultimate or serviceability limit states being exceeded due to thermal movement. In particular the differential movement between components formed from differing materials shall be taken into account in the design. NOTE: The provision of movement joints may also be influenced by moisture and other environmental factors Building structures (1)P The elements of the load bearing structure shall be checked to ensure that thermal movement will not cause exceedance of limit states of the structure, either by the provision of expansion joints or by including the thermal effects in the design. Allowance shall be made for any differential movement between the structure and the cladding. (2)P Structural elements not protected from the external environment by cladding shall be checked to ensure that there is no increase in risk due to higher thermal variations. Where critical (e.g. slabs of environmental protection structures) the effects of solar radiation and uneven temperature distribution shall be considered.

17 Page Cladding elements (1)P The effects of temperature variations shall be considered on cladding elements and the effective length between movement joints shall be determined on the performance of the materials employed in the construction. Where different forms of cladding are used on the structure then account shall be taken of the variations, such as expansion and rate of heat change, between the materials. (2)P The cladding materials shall be fixed to the structure in such a manner as to allow for all differential movement between the various components. (3)P The differential movement due to the variation of the shade air temperature and that due to solar radiation shall be considered in the design of the cladding and its fixings Determination of temperature profiles (1)P The temperature profiles shall be determined on a national basis taking into account the exposure to daily variation of solar radiation and the daily range of the shade air temperature. (2) If specific information on how the effective building temperatures can be correlated with the shade air temperature and solar radiation is available in order to provide reliable effective building temperatures for design, such information should be used to provide characteristic values. (3) For buildings where calculation is needed, a uniform temperature in structural elements may be assumed in most cases. NOTE: Information of shade air temperatures is given in annex A3. The temperatures are applicable to both bridges and buldings.

18 Page 18 Section 6 Temperature changes in bridges 6.1 Bridge decks Bridge deck groupings (1)P A bridge deck shall be considered as one of the following three superstructure groups: Group 1 Steel deck on steel box, truss or plate girders; Group 2 Concrete deck on steel box, truss or plate girders; Group 3 Concrete slab or concrete deck on concrete beams or box girders. NOTE: See also annex B. (2) In the absence of codified values for effective temperatures and temperature differences for other types of bridges, appropriate values should be derived from first principles, specialist data or test results Consideration of thermal actions (1) The following rules apply to bridge decks that are exposed to daily and seasonal climatic effects. Bridges not so exposed may not need to be considered for thermal actions. (2) For bridges, all representative values of thermal actions should be assessed by the uniform temperature component (see 6.1.3) and the linear temperature component (see 6.1.4). (3) In cases where non-linear distributions need to be considered in detail That is in cases where sufficient detailing provisions can not be provided (e.g. composite structure) appropriate temperature differences should be applied. Values are given in annex B Uniform temperature component - characteristic values General (1) The uniform temperature component depends on the minimum and maximum effective bridge temperature which a bridge will achieve over a prescribed period of time. This results in a range of uniform temperature changes which, in an unrestrained structure would result in a change in element length. (2) The following effects can however be produced within a structure due to: Restraint of associated expansion or contraction due to the type of construction (e.g. portal frame, arch, elastomeric bearings); Friction at roller or sliding bearings; Non-linear geometric effects (2nd order effects); For railway bridges the interaction effects between the track and the bridge due to the variation of the temperature of the deck and of the rails induce supplementary horizontal forces in the bearings (and supplementary forces in the rails). For more information, see ENV

19 Page 19 (3)P Minimum and maximum effective bridge temperatures shall be derived from isotherms of minimum and maximum shade air temperatures (see and ). T e.max T e.min maximum 50 Group 1 Group 2 Group Group 3 Group 2 Group minimum T max T min NOTE: For steel truss and plate girders the maximum values given for group 1 may be reduced by 3 o C. Figure 6.1: Correlation between minimum / maximum shade air temperature (T min / T max ) and minimum / maximum effective bridge temperature (T e.min / T e.max ) (4) The effective bridge temperature may be calculated from the shade air temperature using Figure 6.1. The values in Figure 6.1 have been based on daily temperature ranges of 10 o C. Such a range may be considered appropriate for most Member States. If specific data are available to justify a different temperature range the values obtained from Figure 6.1 should be adjusted Shade air temperature (1)P Characteristic values of minimum and maximum shade air temperatures shall be obtained at the site location with reference to the maps of isotherms shown for each Member State in annex A. These shade air temperatures are appropriate to mean sea level in open country with a return period of 50 years. Adjustments for other return periods, height above sea level and local conditions e.g. frost pockets are included in annex A.

20 Page 20 (2) For circumstances where a 50 year return period is deemed inappropriate, the minimum shade air temperatures and the maximum shade air temperatures should be modified in accordance with annex A Range of effective bridge temperatures (1)P The characteristic values of minimum and maximum effective bridge temperatures for restraining forces shall be derived from the minimum (T min ) and maximum (T max ) shade air temperatures by reference to Figure 6.1. The likely effective bridge temperature T o at the time that the structure is effectively restrained shall be taken from annex A as the datum in calculating contraction down to the minimum effective bridge temperature and expansion up to the maximum effective bridge temperature. (2) Thus the characteristic value of maximum range of negative effective bridge temperature, T N,neg should be taken as T N,neg = T e.min - T o (6.1) and the characteristic value of maximum range of positive effective bridge temperature, T N,pos should be taken as T N,pos = T e.max - T o (6.2) NOTE: The overall range of effective bridge temperature T N = T e.max - T e.min (3)P For the design of range of movements (e.g. in the design of bearings and expansion joints), the maximum range of positive effective bridge temperature shall be taken as ( T N,pos + 20 ) o C, and the maximum range of negative effective bridge temperature shall be taken as ( T N,neg - 20 ) o C, if no other provision is required. If the temperature at which the bearings and expansion joints are set is known, then the 20 o C figure in the ranges above can be reduced to 10 o C Linear temperature component - characteristic values Vertical component (1) Over a prescribed period heating and cooling of a bridge deck's upper surface will result in a maximum positive (top surface warmer) and a maximum negative (bottom surface warmer) temperature variation. When materials with different coefficients of linear expansion are used compositely, see annex C. (2) This will produce effects within a structure due to: Restraint of free curvature due to the form of the structure (e.g. portal frame, continuous beams etc.); Friction at rotational bearings; Non-linear geometric effects (2nd order effects).

21 (3) These effects shall be represented by the equivalent positive and negative linear temperature differences as given in Table 6.1. Page 21 Table 6.1: Characteristic values of linear temperature differences for different groups of bridge superstructures Groups of Superstructure (see Annex B) Positive Temperature Difference road bridges Negative Temperature Difference Positive Temperature Difference railway bridges Negative Temperature Difference T M,pos ( o C) T M,neg ( o C) T M,pos ( o C) T M,neg ( o C) Group 1: Steel deck on steel box, truss or plate girders Group 2: Concrete deck on steel box, truss or plate girders Group 3: Concrete deck on concrete box girder concrete T-girder concrete slab [18] [-13] [18] [-13] [15] [-18] [15] [-18] [10] [15] [15] [-5] [-8] [-8] [10] [15] [15] [-5] [-8] [-8] NOTE: Table based on upper bound of linearly varying temperature component for representative sample of bridge geometries. (4) For major bridges (e.g. spans greater than 100 m or where it is considered appropriate) a numerical simulation of the temperature differences considering the method described in annex C may be developed. (5) The temperature differences given in Table 6.1 should be applied between the top and the bottom of superstructure. (6) The values of temperature differences given in Table 6.1 are based on a depth of surfacing of 50 mm for road and railway bridges. For other depths of surfacing these values should be multiplied by factor k sur as given in Table 6.2.

22 Page 22 Table 6.2: Factors k sur to account for different surfacing thickness Road and railway bridges Surface concrete steel composite Thickness top warmer top warmer top warmer than bottom than bottom than bottom bottom warmer than top bottom warmer than top bottom warmer than top (mm) k sur k sur k sur k sur k sur k sur 0 1,5 1) 1,0 1,6 1) 0,6 1,1 0,9 50 1,0 1,0 1,0 1,0 1,0 1, ,7 1,0 0,7 1,2 1,0 1, ,5 1,0 0,7 1,2 1,0 1,0 ballast (60 cm) 0,6 1,0 0,6 1,4 0,8 1,2 NOTE 1: Values represent upper bounds Horizontal component (1) The linear temperature distribution should in general only need to be considered in the vertical direction. In particular cases however, a horizontal temperature gradient may need to be considered. In such cases if no other information is available and no indications for higher values exist 5 o C may be taken as the temperature difference to be used Simultaneity of uniform and linear temperature components (1) If it is necessary to take into account both the temperature difference T M and the uniform temperature component T N assuming simultaneity (e.g. in case of frame structures) the following expression may be used: T M + ω N T N (6.3) or ω M T M + T N (6.4) where the most adverse effect should be chosen and where: ω N = 0,35 ;

23 Page 23 ω M = 0, Differences in effective temperature between different structural elements (1) In certain structures, differences in effective temperature between element types may cause adverse load effects. In addition to the effects resulting from a uniform effective temperature in all elements, the effects resulting from a difference in effective temperature of 15 o C between main structural elements (e.g. tie and arch, suspension / stay cables and deck girder) should be considered. 6.2 Bridge Piers Consideration of thermal actions (1)P Linear temperature differences between the outer faces of bridge piers, hollow or solid, shall be considered in design. (2) Overall temperature effects of piers should be considered, when these can lead to restraining forces or movements in the surrounding structures Temperature differences - characteristic values (1) Characteristic values of the linear temperature differences between opposite outer faces should be taken as 5 o C for concrete piers, hollow or solid, in the absence of detailed information and in the absence of indication of higher values. (2) Characteristic values of the linear temperature differences between the inner and outer faces of the wall should be taken as 15 o C. (3) When considering linear temperature differences for steel columns specialist advice should be obtained.

24 Page 24 Section 7 Temperature changes in industrial chimneys and pipelines 7.1 General (1)P This section only provides quantifiable values for thermal actions from climatic effects, due to the variation of shade air temperature and solar radiation. (2)P Values of operating process temperature shall be obtained from the project specification. (3)P Structures which are in contact with heated gas flow or heated material (e.g. chimneys, pipelines and silos), shall be designed where relevant for the following thermal actions: temperature distribution for normal process conditions; accidental temperature distribution from failures in operation. 7.2 Temperature components characteristic values Shade air temperature (1)P Characteristic values of minimum and maximum shade air temperature shall be obtained at the site location with reference to the maps of isotherms shown for each Member State in annex A. These values of shade air temperature are generally appropriate to mean sea level and local conditions e.g. frost pockets are included in annex A. (2) For circumstances where a 50 year return period is deemed inappropriate, as for transient situations, the values of minimum (maximum) shade air temperature should be modified in accordance with annex A Solar radiation (1)P Chimneys and pipelines which are exposed to daily and seasonal climatic effects will be subjected to solar radiation which will affect the appropriate temperature to be used in design. Characteristic values of solar radiation shall be provided either by National Meteorological Stations or in the project specification Flue gas temperature (1)P Characteristic values (50 year return period) of maximum and minimum flue gas temperature shall be obtained from the project specification Effective element temperature (1) The derivation of characteristic values of effective element temperature will depend on the material configuration, orientation and location of the element and will be a function of the maximum and minimum shade air temperature and the solar radiation. Rules cannot be provided in this Code and recourse will need to be made either to specialist advice or to the use of the indicative values given in Thermal actions to be considered

25 Page 25 (1)P Both the uniform temperature component of the temperature distribution (see Figure 4.1 (a)) and the linearly varying temperature component (see Figure 4.1 (b)) shall be considered. (2)P Solar radiation causing a stepped temperature distribution round the structure s circumference shall be considered. (3)P Uniform and linearly varying temperature components due to process temperature shall be considered. 7.4 Determination of temperature components (1)P The uniform and linearly varying temperature profiles due to climatic effects shall be determined on a national basis taking into account the exposure to the daily variation of the solar radiation and the daily range of the shade air temperature. (2) If specific information on how the effective element temperature can be correlated with the solar radiation and shade air temperature is available in order to provide characteristic values of effective element temperature for design, such information should be used to provide design values. (3)P Characteristic values of the uniform temperature component from liquids or flue gases shall be taken from the project specification. (4)P Linearly varying temperature component from liquids or the gases shall be taken as arising from the difference between the minimum (or maximum) shade air temperature and the characteristic value of the liquid or flue gas temperature, taking into account insulation effects. 7.5 Characteristic values of temperature components (indicative values) (1) In the absence of any specific information on characteristic values of the element temperature the following indicative values may be used. NOTE: These values are based on current experience and they should be checked against any available data to ensure that they are likely to be upper bound values, for the location and type of element under consideration. (2) Characteristic values of the maximum and minimum uniform temperature component should be taken as those of the maximum and minimum shade air temperature (see 7.2.1). (3) For concrete chimneys and concrete pipelines characteristic values of the linear temperature differences between the inner and outer faces of the wall should be taken as 15 o C. (4) For concrete chimneys and concrete pipelines a stepped temperature distribution round the structure s circumference (causing both overall and local thermal effects) should be considered on the basis that one 90 o quadrant of its curcumference has a mean temperature 15 o C higher than that of the remainder of the circumference.

26 Page 26 (5) When considering steel chimneys and steel pipelines, the linear temperature difference and stepped temperature distribution round the structure s circumstance should be set down in the project specification or specialist advice should be obtained. 7.6 Simultaneity of actions (1) When considering thermal actions due to climatic effects only, the following components should take account of simultaneity: a) uniform temperature component (see 7.5 (2) and Figure 7.1 (a)); b) the stepped distribution (see 7.5 (4) and Figure 7.1 (b)); c) linear temperature differences between the inner and the outer faces of the wall (see 7.5 (3) and Figure 7.1 (c)). (2) When considering a combination of thermal actions due to climatic effects with those due to process effects (liquids or flue gases) the following components should take into account simultaneity: uniform temperature component due to flue gas temperature (see 7.4 (3)); linear temperature differences (see 7.4 (4)); the stepped distribution (see 7.5 (4)). (3) Where stepped temperature distribution is considered, it should be combined with wind effects (including vortex shedding and ovalisation) at the appropriate wind speed to cause maximum response from these effects.

27 Page 27 (a) Uniform temperature component T N 90 o 15 o C (b) Stepped temperature distribution round the circumference outer face warmer T M (c) Linear temperature differences between the inner and the outer faces of the wall inner face warmer T M Figure 7.1: Relevant temperature components for industrial chimneys and pipelines

28 Page 28 Annex A (Informative) Isotherms of national minimum and maximum shade air temperatures A.1 General (1) This annex contains maps of isotherms of both annual minimum and annual maximum shade air temperatures for Member States. (2) The maps represent 50 year return period values. These values may need to be adjusted for height above see level according to A.3. However in the absence of this information the values of shade air temperature should be adjusted for height above sea level by subtracting 0,5 o C per 100 m height for minimum shade air temperature and 1,0 o C per 100 m height for maximum shade air temperature. (3) There are locations where the minimum values diverge from the values given as, for example, frost pockets and sheltered low lying areas where the minimum may be substantially lower, or in large conurbations and coastal sites, where the minimum may be higher, than that indicated in the relevant figures. These divergences should be taken into consideration using local meteorological data. (4) The datum temperature T 0 should be taken from the information provided by each Member State in this annex. In the absence of specific values, T 0 should be taken as 10 o C. A.2 Maximum and minimum shade air temperature values for return periods other than 50 years (1) If T max,r (T min,r ) is value of maximum (minimum) shade air temperature with mean return period R other than 50 years the ratio T max,r /T max (T min,r /T min ) may be determined from Figure A2.1, based on UK data. (2) In general T max,r (T min,r ) may be found using the following expressions based on a type I extreme value distribution: for maximum: T max,r = T max {k 1 - k 2 ln[-ln(1-1/r) ] } (A.1) for minimum: T min,r = T min {k 3 + k 4 ln[-ln(1-1/r) ] } (A.2) where: T max (T min ) is the value of maximum (minimum) shade air temperature with return period 50 years; k 1 = (uc) / { (uc) + 3,902 } (A.3) k 2 = 1 / { (uc) + 3,902 } (A.4) where: u, c are location and scale parameters of annual maximum shade air temperature distribution;

29 Page 29 k 3 = (uc) / { (uc) - 3,902 } k 4 = 1 / { (uc) - 3,902 } (A.5) (A.6) where: u, c are location and scale parameters of annual minimum shade air temperature distribution. Coefficients k 1, k 2, k 3 and k 4 should be based on values of u and c given by national responsible authorities. In the absence of specific data the following values based on U.K. data may be used: k 1 = 0,781; k 2 = 0,056; k 3 = 0,393; k 4 = - 0,156. The ratios T max,r /T max and T min,r /T min respectively may then be taken from Figure A.1. R maximum minimum Ratios Figure A.1: Ratios T max,r / T max and T min,r / T min

30 Page 30 A.3 List of national maps of isotherms of minimum and maximum shade air temperatures A.3.1 A.3.2 A.3.3 A.3.4 A.3.5 A.3.6 A.3.7 A.3.8 A.3.9 Map of Austria Map of Belgium Map of Czech Republic Map of Denmark Map of Finland Map of France Map of Germany Map of Greece Map of Iceland A.3.10 Map of Ireland A.3.11 Map of Italy A.3.12 Map of Luxembourg A.3.13 Map of Netherlands A.3.14 Map of Norway A.3.15 Map of Portugal A.3.16 Map of Slovakia A.3.17 Map of Spain A.3.18 Map of Sweden A.3.19 Map of Switzerland A.3.20 Map of United Kingdom

31 Page 31 A.3.2 Belgium (1) Isotherms of minimum shade air temperature in o C

32 Page 32 A.3.2 Belgium (2) Isotherms of maximum shade air temperature in o C

33 Page 33 A.3.3 Czech Republic (1) Isotherms of minimum shade air temperature in o C

34 Page 34 A.3.3 Czech Republic (1) Isotherms of maximum shade air temperature in o C

35 Page 35 A.3.5 Finland (1) Isotherms of minimum shade air temperature in o C

36 Page 36 A.3.5 Finland (2) Isotherms of maximum shade air temperature in o C

37 Page 37 A.3.7 Germany (1) Isotherm of minimum shade air temperature In general the minimum shade air temperature may be taken as -24 C. (2) Isotherm of maximum shade air temperature In general the maximum shade air temperature may be taken as +37 C.

38 Page 38 A.3.10 Ireland (1) Isotherms of minimum shade air temperature in o C k 3 = 0,500 k 4 = - 0,130

39 Page 39 A.3.10 Ireland (2) Isotherms of maximum shade air temperature in o C k 1 = 0,800 k 2 = 0,052

40 Page 40 A.3.11 Italy (UNOFFICIAL MAP) (1) Isotherms of minimum shade air temperature in o C

41 Page 41 A.3.11 Italy (UNOFFICIAL MAP) (2) Isotherms of maximum shade air temperature in o C

42 Page 42 A.3.12 Luxemburg (1) Isotherm of minimum shade air temperature In general the minimum shade air temperature may be taken as -24 C. (2) Isotherm of maximum shade air temperature In general the maximum shade air temperature may be taken as +37 C.

43 Page 43 A.3.13 Netherlands (1) Isotherm of minimum shade air temperature In general the minimum shade air temperature may be taken as -22 C. For coastal provinces N -Holland, Z -Holland and Zeeland the minimum shade air temperature may be taken as -17 C. (2) Isotherm of maximum shade air temperature In general the maximum shade air temperature may be taken as +38 C. For coastal provinces N -Holland, Z -Holland and Zeeland the maximum shade air temperature may be taken as +35 C.

44 Page 44 A.3.16 Slovakia (1) Isotherms of minimum shade air temperature in o C

45 Page 45 A.3.16 Slovakia (2) Isotherms of maximum shade air temperature in o C

46 Page 46 A.3.17 Spain (1) Isotherms of minimum shade air temperature in o C Values have been determined using the following method: temperature data from 1961 to 1990; adjustments have been made using an extreme value distribution function. Maximum likelihood; 50 years return period; 90 per cent confidence level; the map has been developed using Kriging linear method.

47 Page 47 A.3.17 Spain (2) Isotherms of maximum shade air temperature in o C Values have been determined using the following method: temperature data from 1961 to 1990; adjustments have been made using an extreme value distribution function. Maximum likelihood; 50 years return period; 90 per cent confidence level; the map has been developed using Kriging linear method.

48 Page 48 A.3.18 Sweden (1) Isotherms of minimum shade air temperature in o C Data represent calculated 50 year observation period modal values of annual minimum observed temperatures. Significant local deviations are to be expected in response to topography and urban development.

49 Page 49 A.3.18 Sweden (2) Isotherms of maximum shade air temperature in o C Data represent calculated 50 year observation period modal values of annual maximum observed temperatures. Significant local deviations are to be expected in response to topography and urban development.

50 Page 50 A.3.19 Switzerland (1) Isotherm of minimum shade air temperature In general the minimum shade air temperature may be taken as: North of the Alps -28 C; South of the Alps -20 C. (2) Isotherm of maximum shade air temperature In general the maximum shade air temperature may be taken as: North of the Alps +38 C; South of the Alps +36 C.

51 Page 51 A.3.20 United Kingdom (1) Isotherms of minimum shade air temperature in o C

52 Page 52 A.3.20 United Kingdom (2) Isotherms of maximum shade air temperature in o C

53 Page 53 Annex B (Normative) Models for the assessment of non-linear thermal actions in bridges NOTE: The content of this annex may be brought into the main text at the EN stage in the light of use by the Member States. B.1 General (1) This annex contains tables of positive and negative temperature difference profiles. (2) Temperature difference profiles are presented for each of the three basic superstructure groups shown in Figure B.1 for a variety of surfacing conditions. (3) The temperature difference profiles presented are defined in the following tables and figures. B.2 Effect of surfacing depths (1) The values of the temperature differences given in Figure B.1 may be used. The values are valid for 40 mm surfacing depths for superstructure group 1 and 100 mm surfacing depths for groups 2 and 3. For other depths of surfacing, the values given in tables B.1 to B.3 should be used. Table B.1: Values of T for superstructure group 1 Surfacing thickness mm Positive temperature difference profile Negative temperature difference profile T 1 T 2 T 3 T 4 T 1 o C o C o C o C o C unsurfaced [30] [27] [24] [16] [15] [14] [6] [9] [8] [3] [5] [4] [8] [6] [6]

54 Page 54 Figure B.1: Temperature difference for different groups of superstructure

55 Table B.2: Values of T for superstructure group 2 Page 55 Depth of slab (h) Surface thickness Positive temperature difference m mm Negative temperature difference T 1 T 1 o C o C 0,2 unsurfaced waterproofed [16,5] [23,0] [18,0] [13,0] [10,5] [8,5] [5,9] [5,9] [4,4] [3,5] [2,3] [1,6] 0,3 unsurfaced waterproofed [18,5] [26,5] [20,5] [16,0] [12,5] [10,0] [9,0] [9,0] [6,8] [5,0] [3,7] [2,7]

56 Page 56 Table B.3: Values of T for superstructure group 3 Depth of slab (h) Surfacing thickness Positive temperature difference Negative temperature difference m mm 0,2 unsurfaced waterproofed T 1 T 2 T 3 T 1 T 2 T 3 T 4 o C [12,0] [19,5] [13,2] [8,5] [5,6] [3,7] o C [5,0] [8,5] [4,9] [3,5] [2,5] [2,0] o C [0,1] [0,0] [0,3] [0,5] [0,2] [0,5] o C [4,7] [4,7] [3,1] [2,0] [1,1] [0,5] o C [1,7] [1,7] [1,0] [0,5] [0,3] [0,2] o C [0,0] [0,0] [0,2] [0,5] [0,7] [1,0] o C [0,7] [0,7] [1,2] [1,5] [1,7] [1,8] 0,4 unsurfaced waterproofed [15,2] [23,6] [17,2] [12,0] [8,5] [6,2] [4,4] [6,5] [4,6] [3,0] [2,0] [1,3] [1,2] [1,0] [1,4] [1,5] [1,2] [1,0] [9,0] [9,0] [6,4] [4,5] [3,2] [2,2] [3,5] [3,5] [2,3] [1,4] [0,9] [0,5] [0,4] [0,4] [0,6] [1,0] [1,4] [1,9] [2,9] [2,9] [3,2] [3,5] [3,8] [4,0] 0,6 unsurfaced waterproofed [15,2] [23,6] [17,6] [13,0] [9,7] [7,2] [4,0] [6,0] [4,0] [3,0] [2,2] [1,5] [1,4] [1,4] [1,8] [2,0] [1,7] [1,5] [11,8] [11,8] [8,7] [6,5] [4,9] [3,6] [4,0] [4,0] [2,7] [1,8] [1,1] [0,6] [0,9] [0,9] [1,2] [1,5] [1,7] [1,9] [4,6] [4,6] [4,9] [5,0] [5,1] [5,1] 0,8 unsurfaced waterproofed [15,4] [23,6] [17,8] [13,5] [10,0] [7,5] [4,0] [5,0] [4,0] [3,0] [2,5] [2,1] [2,0] [1,4] [2,1] [2,5] [2,0] [1,5] [12,8] [12,8] [9,8] [7,6] [5,8] [4,5] [3,3] [3,3] [2,4] [1,7] [1,3] [1,0] [0,9] [0,9] [1,2] [1,5] [1,7] [1,9] [5,6] [5,6] [5,8] [6,0] [6,2] [6,0] 1,0 unsurfaced waterproofed [15,4] [23,6] [17,8] [13,5] [10,0] [7,5] [4,0] [5,0] [4,0] [3,0] [2,5] [2,1] [2,0] [1,4] [2,1] [2,5] [2,0] [1,5] [13,4] [13,4] [10,3] [8,0] [6,2] [4,3] [3,0] [3,0] [2,1] [1,5] [1,1] [0,9] [0,9] [0,9] [1,2] [1,5] [1,7] [1,9] [6,4] [6,4] [6,3] [6,3] [6,2] [5,8] 1,5 unsurfaced waterproofed [15,4] [23,6] [17,8] [13,5] [10,0] [7,5] [4,5] [5,0] [4,0] [3,0] [2,5] [2,1] [2,0] [1,4] [2,1] [2,5] [2,0] [1,5] [13,7] [13,7] [10,6] [8,4] [6,5] [5,0] [1,0] [1,0] [0,7] [0,5] [0,4] [0,3] [0,6] [0,6] [0,8] [1,0] [1,1] [1,2] [6,7] [6,7] [6,6] [6,5] [6,2] [5,6]