EUROPEAN PRESTANDARD ENV PRÉNORME EUROPÉENNE EUROPÄISCHE VORNORM

Transcription

1 EUROPEAN PRESTANDARD ENV PRÉNORME EUROPÉENNE EUROPÄISCHE VORNORM English version EUROCODE 1 : Basis of design and actions on structures Part 2-7 : Accidental actions due to impact and explosions Final Draft June 1998 CEN European Committee for Standardization Comité Européen de Normalisation Europäisches Komitee für Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels CEN 1998 Copyright reserved to all CEN members Ref.No

2 Page 2 Contents Page FOREWORD GENERAL SCOPE NORMATIVE REFERENCES DISTINCTION BETWEEN PRINCIPLES AND APPLICATION RULES DEFINITIONS SYMBOLS CLASSIFICATION OF ACTIONS DESIGN SITUATIONS DEFINITION OF ACCIDENTAL DESIGN SITUATIONS AND ACCIDENTAL ACTIONS DESIGN FOR ACCIDENTAL SITUATIONS IMPACT FIELD OF APPLICATION REPRESENTATION OF ACTIONS ACCIDENTAL ACTIONS CAUSED BY VEHICLES ACCIDENTAL ACTIONS CAUSED BY RAIL TRAFFIC UNDER BRIDGES OR NEAR OTHER STRUCTURES ACCIDENTAL ACTIONS CAUSED BY SHIPS ACCIDENTAL ACTIONS CAUSED BY HELICOPTERS EXPLOSIONS FIELD OF APPLICATION REPRESENTATION OF ACTIONS EXPLOSIONS IN ROOMS WITH VENTING PANELS...26 ANNEX A (INFORMATIVE) ADVANCED IMPACT DESIGN A.1 GENERAL...28 A.2 IMPACT DYNAMICS...28 A.3 IMPACT FROM TRUCKS AND LORRIES...29 A.4 IMPACT BY TRAINS...32

3 Page 3 ANNEX B (INFORMATIVE) EXPLOSIONS B.1 GENERAL...34 B.2 STRUCTURES IN CATEGORY B.3 DUST EXPLOSIONS...34 B.4 EXPLOSIONS IN TUNNELS...36 ANNEX C (INFORMATIVE) ADDITIONAL GUIDANCE FOR DESIGN C.1 ACCEPTABLE LOCALISED DAMAGE IN BUILDINGS...38 C.2 SIMPLIFIED ANALYSIS FOR CATEGORY 2 STRUCTURES IN BUILDINGS...38 C.3 PREVENTIVE AND PROTECTIVE MEASURES AGAINST RAIL TRAFFIC UNDER BRIDGES... 38

4 Page 4 Foreword Objectives of the Eurocodes (1) The "Structural Eurocodes" comprise a group of standards 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 harmonised technical specifications 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 harmonised technical rules for the design of buildings 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/TC250 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 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 clause and the scope of this Part of Eurocode 1 is defined in clause Additional Parts of Eurocode 1 which are planned are indicated in clause (17) This Part is complemented by three informative annexes. (18) Accidental actions are described in different parts of Eurocode 1. In particular, ENV includes accidental actions due to impact on structural elements of bridges. In the relevant sections of ENV design values are listed, which have to be taken into account for the design situations of impact. This Part and ENV are consistent with regard to the design values.

6 Page 6 (19) Design situations endangered by accidental actions may be categorised. The categorisation may follow national traditions and preferences. The categorisation will be a matter for relevant authorities.

7 Page 7 Section 1 General 1.1 Scope Scope of ENV 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 ENVs (2) It may also be used as a basis for the design of structures not covered in ENVs and where either 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 specified design procedures should be used Scope of ENV Accidental actions due to impact and explosions (1)P This Part describes the possible safety strategies in case of general accidental situations and it covers in detail the accidental actions due to impact and internal explosions. Consideration of accidental actions described in this Part includes actions caused by human activities but excludes actions arising from external explosions, warfare and sabotage. Also, this Part does not refer to some events, which are generally considered as accidents, but which do not result in structural damage (e.g. persons falling through roof claddings). (2) Accidental actions arising from the natural phenomena such as tornadoes, extreme erosion or falling rocks are not included. However, they may be incorporated in design using principles similar to those contained in this Part. (3)P Structures exposed to fire shall be designed in accordance with ENV "Actions on structures exposed to fire" in conjunction with the relevant fire design Parts of ENVs 1992 to 1996 and ENV (4)P Structures exposed to seismic events shall be designed according to ENV 1998 "Earthquake resistant design of structures". (5)P This Part defines the general principles that can be used in the analysis of accidental design situations and describes: the procedure for a risk analysis to identify extreme events, the causes and consequences of undesired events;

8 Page 8 the safety precautions required to maintain a safety level which complies with the acceptance criteria, by using adequate measures to reduce the probability or the consequences of the extreme events. (6) In particular this Part specifies: recommended design models for the most common cases of accidental actions arising from impact and explosions; detailing provisions which may be used as alternatives to design verifications. (7) Accidental actions given in Section 4 are related to impacts and collisions from the following sources: vehicles; derailed trains; ships; the hard landing of helicopters on roofs. (8) Three informative annexes are included : Annex A describes an advanced impact design concept; Annex B includes an advanced explosion design concept; Annex C gives additional guidance for design Further Parts of ENV 1991 (1) Further Parts of ENV 1991 which, at present, either are being prepared or are planned, are given in clause Normative references (1) This European Prestandard incorporates by either dated or undated reference, provisions from other standards. These normative references are cited in the appropriate places in the text and are listed below. ISO Basis of design for structures Notations. General symbols. ISO DP Accidental actions due to human activities. ISO 6184-a Explosion protection systems - Part 1: Determination of explosion indices of combustible dusts in air. UIC SC 7J Report 777/2R (May 1996): Structures built over railway lines.

9 Page 9 NOTE: The following European Prestandards which either are published or are in preparation are cited at the appropriate places in the text and are listed below. ENV ENV ENV ENV ENV ENV ENV ENV ENV ENV ENV 1992 ENV 1993 ENV 1994 ENV 1995 ENV 1996 ENV 1997 ENV 1998 ENV 1999 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 and imposed loads Eurocode1 : 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 loads Eurocode 1 : Basis of design and actions on structures Part 2.5 : Thermal 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 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 Eurocode 8 : Earthquake resistant design of structures Eurocode 9 : Design of aluminium alloy structures

10 Page Distinction between principles and application rules (1) Depending upon the character of the individual clauses, distinction is made in this Part 2-7 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 2-7 of ENV 1991 the application rules are identified by a number in brackets, e.g. as this clause. 1.4 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 of ENV Accidental actions: Action, usually of short duration, which is unlikely to occur with a significant magnitude over a period of time under consideration during the design working life Explosion: Rapid chemical reaction of dust or gas in air. It results in high temperatures and high overpressures. Explosion pressures propagate as pressure waves Deflagration: Explosion where the continuation of the chemical reaction is caused by the transport of heat. The flame front travels through the mixture at a subsonic speed, in the order of 100 m/s. The pressure waves travel with the local speed of sound. Peak pressure values may vary from 10 to 1 500kN/m Detonation: Explosion where the continuation of the chemical reaction is caused by a pressure shock wave travelling at a supersonic speed generally more than m/s. A typical value for the pressure is kn/m 2 but the peak duration is very short (10 ms) Key element: An element of the structure, essential for the overall stability of the structure, the failure of which would cause disproportionate damage and/or collapse of the structure Risk: Risk is expressed in terms of possible consequences of the event and the associated probability.

11 Page Risk reducing measures: Risk reducing measures consist of measures to reduce the probability of the accident and measures to reduce the consequence, including contingency plans, of an accident Hazard scenarios: Events caused by natural phenomena or human activities which may endanger the structural safety. A hazard scenario is characterised by one predominant action. 1.5 Symbols (1) For the purpose of this Prestandard, the following symbols apply. NOTE: The notation used is based on ISO 3898:1987. (2) A basic list of notations is provided in ENV , Basis of design and the additional notations below are specific to this Part. Latin upper case letters A v the area of venting components F impact or collision force F d,x horizontal static equivalent impact load in direction of normal travel F d,y horizontal static equivalent impact load perpendicular to the direction of normal travel V Volume of room W weight of a loaded truck Latin lower case letters d diameter or equivalent diameter f friction coefficient h height l length m mass p probability p d nominal equivalent static pressure p v uniformly distributed static pressure r a multiplication factor s distance Greek lower case letters adjustment factor α Q θ angle of hit

12 Page 12 Section 2 Classification of actions (1)P According to ENV "Basis of design" actions arising from impact and explosions shall be classified as accidental actions. (2) For these accidental actions the representative value is generally a design value. The specifications of the models for determining the design values are given in Section 4 for impacts and Section 5 for explosions respectively.

13 Page 13 Section 3 Design situations 3.1 Definition of accidental design situations and accidental actions (1)P In the accidental design situation, as defined in ENV , the occurrence of exceptional events and corresponding accidental actions shall be considered, in combination with permanent and variable loads. Additionally, in some cases it may be necessary to consider also the period of time shortly after the occurrence of the exceptional event. (2) The actions in the case of accidental design situations are usually actions with a low probability of occurrence, which have severe consequences and are usually of short duration. (3)P The selected design situations shall be sufficiently severe and varied as to encompass all conditions which can be reasonably foreseen to occur during the execution and use of the structure. In this case "which can be reasonably foreseen" shall be interpreted as "which have a low but reasonable probability of occurrence. (4) A severe possible consequence requires the consideration of extensive hazard scenarios, while less severe consequences allow less extensive hazard scenarios. Consequences may be assessed in terms of injury and death to people, unacceptable change to the environment, large economic losses for the society, and so on. NOTE 1: ISO DP "Accidental Actions due to Human Activities" specifies that the representative value of an accidental action should be chosen in such a way that there is an assessed probability less than p = 10-4 per year for one structure that this or a higher impact energy will occur. However, only in some cases can the probability of occurrence of an accidental action and the probability distribution of its magnitude be determined from statistics and risk analysis procedures. Design values in practice are often nominal values. NOTE 2: In some cases accidental actions and variable actions may originate from the same sources of action. For instance, this may be the case for impact from ships, where a ship out of control may be the source of an accidental action, whereas actions from fendering and mooring of ships are variable actions. Similar examples may be found for cars in garages. (5) Sequences of accidental events are not within the scope of this Part. 3.2 Design for accidental situations (1)P Accidental actions shall be accounted for, when specified, in the design of a structure depending on: the possible consequences of damage to the structure; the probability of occurrence of the initiating event; the provisions taken for preventing or reducing the dangers involved and the exposure of the structure; the level of acceptable risk.

14 Page 14 (2)P No structure can be expected to resist all actions that could arise due to an extreme cause, but there shall be a reasonable probability that it will not be damaged to an extent disproportionate to the original cause. NOTE: In practice, the occurrence and consequences of accidental actions can be associated with a certain risk level. If this level cannot be accepted, additional measures are necessary. A zero risk level, however, will only seldom be reached and in most cases it is necessary to accept a certain level of residual risk. This final risk level will be determined by the cost of safety measures weighed against the perceived public reaction after an accident. The risk should also be based on a comparison with risks generally accepted by society in comparable situations. In defining the acceptable risk levels the Relevant and National Authorities play an important role. (3) Localised damage due to accidental actions may be acceptable, provided that it will not endanger the whole structure or that the loadbearing capacity is maintained during an appropriate length of time for necessary emergency measures to be taken, for instance evacuation of the building and its surroundings. (4) Measures to control the risk in the case of accidental actions may pursue as appropriate one or more of the following strategies: preventing the action from occurring or reducing to a reasonable level the probability and/or magnitude of the action; protecting the structure against the effects of an action by reducing the actual loads on the structure (e.g. protective bollards); designing in such a way that neither the whole structure nor a significant part of it will collapse if a local failure (e.g. single element failure) occurs; designing key elements, on which the structure is particularly reliant, with special care, and for appropriate accidental actions; applying minimum prescriptive design/detailing rules which in normal circumstances provide an acceptably robust structure (e.g. three-dimensional tying for additional resistance, or minimum level of ductility of structural elements subject to impact); providing additional prescriptive design/detailing rules in order to obtain the residual stability requisite for a safe evacuation of the occupants; applying the principles of capacity design (examples: limiting strength of parapets on bridges to avoid damage to the main structural system or installing venting components with a low mass and strength to reduce the effect of explosions); providing measures to mitigate the consequences of structural failure. In the structural design the presence of preventive and protective measures should be regarded as design assumptions (see ENV , Basis of design, clause 1.3). NOTE 1: Strategies may be mixed in the same design procedure. Prescriptive rules are provided in the relevant ENVs 1991 to 1999.

15 Page 15 NOTE 2: The limited effect of preventing actions must be recognised; it is dependent upon factors which, over the life span of the structure, are commonly outside the control of the structural design process. The responsibility of the maintenance of the preventive measures is often a matter for the relevant authority. (5) Accidental design situations may be categorized as follows: Category 1 Limited consequences; Category 2 Medium consequences; Category 3 Large consequences. For facilitating the design of certain types of structures it might be appropriate to treat some parts of the structure as belonging to a different category from the overall structure. This might be the case for parts that are structurally separated and differ in exposure and consequences. NOTE: The categorization may follow national traditions and preferences, and the actual categorization will be a matter for the relevant authorities. (6) The different categories may be considered in the following manner: Category 1 : no specific consideration is necessary with regard to accidental actions; Category 2 : depending upon the specific circumstances of the structure in question: a simplified analysis by static equivalent action models may be adopted or prescriptive design/detailing rules may be applied; Category 3 : a more extensive study recommended, using dynamic analyses, non-linear models and load structure interaction if considered appropriate. NOTE: The effect of preventive and/or protective measures is that the probability of damage to the structure is reduced. For design purposes this can sometimes be taken into consideration by assigning the structure to a lower category class. In other a reduction of forces on the structure may be more appropriate. (7) In this standard, Section 4 includes values which may be used in analyses for accidental impacts, and Section 5 deals with gas explosions.

16 Page 16 Section 4 Impact 4.1 Field of application (1) The actions presented in this section should be applied to those structural elements or, if appropriate, to their protection systems where the consequences of failure in the corresponding design situations are considered to be in the categories 2 and 3 as defined in Section 3. NOTE: The design of structures in Category 3 may also consider the use of other more rigorous types of analysis as described in Annex A. These analyses may be expected to give different results. (2) This section defines actions due to impact for: collisions from vehicles; collisions from trains; collisions from ships; the hard landing of helicopters on roofs. (3) Buildings to be considered are parking garages, buildings in which vehicles are driven, warehouses in which forklift trucks are driven and buildings that are located in the vicinity of either road or railway traffic. (4) For bridges the actions due to impact to be considered depends upon the type of traffic under and over the bridge. (5) Actions due to impact from helicopters need to be considered only for those buildings where the roof contains a designated landing pad. 4.2 Representation of actions (1)P The impact process is determined by the mass distribution, deformation behaviour, damping characteristics and initial velocities of both the impacting body and the structure. To find the forces at the interface, the object and the structure shall be considered as one integrated system. (2)P When defining the material properties of the impacting body and of the structure, upper or lower characteristic values shall be used, when appropriate; additionally, strain rate effects shall be taken into account, when appropriate. (3)P Actions due to impact shall be considered as free actions. The areas where actions due to impact need to be considered shall be specified individually depending on the cause. (4) For structural design purposes the actions due to impact may be represented by an equivalent static force giving the equivalent action effects in the structure. This simplified model may be used for the verification of static equilibrium or for strength verifications, depending on the protection aim.

17 Page 17 (5) For structures which are designed to absorb impact energy by elastic-plastic deformations of members, the equivalent static loads may be determined by considering both plastic strength and deformation capacity of such members. (6) For structures for which the energy is mainly dissipated by the impacting body, equivalent static forces may be taken from clauses 4.3 to Accidental actions caused by vehicles Actions from vehicle traffic under bridges or other structures (1) In the case of hard impact, design values for the horizontal actions due to impact on vertical structural elements (e.g. columns, walls) in the vicinity of various types of roads may be obtained from Table 4.1. Table 4.1: Horizontal static equivalent design forces due to impact on supporting substructures of bridges or other structures over roadways Type of road Type of vehicle Force F d,x motorway urban area courtyards truck truck passenger cars only trucks (kn) [1 000] [500] Force F d,y (kn) parking garages passenger cars only [40] [25] NOTE 1: x = direction of normal travel, y = perpendicular to the direction of normal travel. [50] [150] [500] [250] NOTE 2: The values in the table are applicable to normally exposed structural elements; in special cases for category 3 types of structures a more advanced analysis as indicated in Annex A might be more appropriate. In particular Annex A gives information on design velocities, duration of the loads and the effect of the distance from the road to the structural element. (2) The forces F d,x and F d,y need not be considered simultaneously. (3) For car impact on vertical members the resulting collision force F on the structure should be applied at 0,5 m above the level of the driving surface (see Figure 4.1). The force application area may be taken as 0,25 m (height) by 1,50 m (width) or the member width, whichever is the smaller. [25] [75] 1 The statements in this clause are compatible to those in ENV , clause 4.7. It is envisaged that the clauses relating to impact in ENV will be deleted when it is converted to an EN.

18 Page 18 (4) For impact from trucks and lorries on vertical members the resulting collision force F on the structure should be applied at 1,25 m above the level of the driving surface (see Figure 4.1). The force application area is 0,5 m (height) by 1,50 m (width) or the member width, whichever is the smaller. (5) Actions due to impact loads from trucks and lorries on horizontal structural elements above traffic lanes need only be considered, when minimum values for clearances or other suitable protection measures to avoid impact are not provided. (6) In case where verifications of static equilibrium or strength or deformation capacity are required for impact loads from trucks on horizontal structural elements above traffic lanes, the following rules may be applied (see Figure 4.2): on vertical surfaces the design impact loads are equal to those given in Table 4.1, multiplied by a factor r (see Figure 4.3); on the under side surfaces the same impact loads as above with an upward inclination of 10 o should be considered. NOTE 1: The values may depend upon national legal limits and/or other local circumstances such as other bridges above the same road. NOTE 2: Information on the effect of the distance s can be found in Annex A. The force application area may be taken as 0,25 m (height) by 0,25 m (width). (7) For buildings where fork lift trucks are present on a regular basis, a horizontal static equivalent design force F = 5W, where W is the weight of a loaded truck, should be taken into account at a height of 0,75 m above floor level.

19 Page m or member width whichever is the smallest d s Direction of travel Figure 4.1: Collision force on structural elements near traffic lanes F F driving direction h h Figure 4.2: Collision force on horizontal structural elements above traffic lanes

20 Page 20 r F h 0,5 0,0 5,0 m 6,0 m h Figure 4.3: Value of the factor r for collision forces on horizontal structural elements above traffic lanes, depending on the free height h

21 Page Actions from vehicles on the bridge Collision forces on safety barriers 2 (1) For structural design, a horizontal vehicle collision force transferred to the bridge deck by rigid safety barriers 100 kn should be applied acting transversely and horizontally 100 mm below the top of the barrier or 1,0 m above the level of the carriageway or footway, whichever is lower. This force should be applied on a line 0,5 m long. The vertical traffic load acting simultaneously with the collision force should be taken as 50 % of the characteristic axle load, including the adjustment factor α Q, as specified in ENV Collision forces on structural members (1) The vehicle collision forces on vertical structural end members above carriageway levels are the same as specified in (1) and are given in Table Accidental actions caused by rail traffic under bridges or near other structures (1) Design values for the horizontal static equivalent forces due to impact on vertical structural elements (e.g. columns, walls) for various design situations are given in Table 4.2. Table 4.2 : Horizontal static equivalent design forces due to impact on supporting substructures of bridges or other structures over railways Distance s from structural elements to the centreline of the nearest track (m) Force F d,x (kn) Force F d,y (kn) continuous walls s < 3 m [0] [1500] non-continuous walls s < 3 m first element: [10 000] other elements [4 000] first element : [3 500] other elements: [1 500] 3 m s 5 m [4 000] [1 500] s > 5 m [0) [0] NOTE : x = track direction, y = perpendicular to track direction 2 See also, when available, technical approvals or standards established by CEN/TC 226.

22 Page 22 (2) The horizontal static equivalent design forces, given in Table 4.2 are applicable for situations where the maximum permitted line speed is less or equal to 120 km/h. For speeds above 120 km/h, the values of the horizontal static equivalent design forces together with additional preventative and/or protective measures should be determined. (3) If the maximum permitted line speed is lower or equal to 50 km/h, the forces in Table 4.2 may be multiplied by 0,5. (4) The forces F d,x and F d,y should be applied at a level of 1,8 m above track level and need not be considered simultaneously. The impact area should be taken as 1 m high by 2 m wide. (5) For supports which are situated within solid platforms or surrounded by a solid plinth at least 0,55 m above top of the rail, the equivalent loads allocated may be reduced by half. (6) For end walls a design force of F dx = kn for passenger trains and F d,x = kn for shunting and marshalling trains should be taken into account. These forces should be applied at a level of 1,0 m above track level. (7) Impact on the superstructure (deck structure) due to rail traffic under a bridge need not be considered. Rail traffic under a bridge may be assumed to impact the substructure only. 4.5 Accidental actions caused by ships (1) The characteristics to be considered for collisions from ships depend upon the type of waterway, the type of vessels and their impact behaviour and the type of the structures and their energy dissipation characteristics. The types of vessels that can be expected should be classified according to standard ship characteristics, see Tables 4.3 and 4.4. (2) In case more accurate calculations are not carried out and the energy dissipation of the structure can be neglected, the static equivalent forces according to Tables 4.3 and 4.4 may be applied. NOTE: Information on the duration of the load can be found in Annex A.

23 Page 23 Table 4.3: Ship characteristics and corresponding nominal horizontal static equivalent design forces for inland waterways CEMT 1) class Length l Mass m Reference Mass of freight m (ton) Force F d (m) (ton) (kn) I [4 000] II [5 000] III [6 000] IV [7 000] Va [11 000] Vb [15 000] VIa [11 000] VIb [15 000] VIc [22 000] VII [22 000] 1) CEMT : European Conference of Ministers of Transport, classification proposed 19 June 1992, approved by the Council of European Union 29 October Table 4.4: Ship characteristics and corresponding nominal horizontal static equivalent design forces for sea waterways Class of ship Length l (m) Mass m (ton) Force F d (kn) small [15 000] medium [25 000] large [40 000] very large [80 000] NOTE : The forces given correspond to a velocity of about 2,0 m/s. (3) In harbours the forces given in Tables 4.3 and 4.4 may be reduced by a factor of 0,5. (4) Bow, stern and broad side impact should be considered where relevant; for side and stern impact the forces given in Tables 4.3 and 4.4 may be multiplied by a factor of 0,3. (5) Bow impact should be considered for the main sailing direction with a maximum deviation of 30 o. (6) If a wall structure is hit at an angle θ, the following forces should be considered: perpendicular to the wall: F d,y = F d sin θ (4.1) in wall direction: F d,x = f F d sin θ (4.2)

24 Page 24 where: F is the collision force at θ = 90 ; f is the friction coefficient, f = 0,4. (7) The point of impact depends upon the geometry of the structure and the size of the vessel. As a guideline the most unfavourable impact point may be taken as ranging from 0,05l below to 0,05l above the design water levels (see Figure 4.4). The impact area is 0,05l high and 0,1l broad, unless the structural element is smaller (l = ship length). (8) The forces on a structure depend upon the height of the structure and the type of ship to be expected. In general the force on the superstructure of the bridge will be limited by the yield strength of the ships superstructure. A maximum of 10 percent of the bow impact force may be considered as a guideline. Figure 4.4 : Possible impact areas for ship collision (9) Under certain conditions it might be necessary to consider the possibility that the ship is lifted by an abutment or foundation block and collides with columns on top of them.

25 Page Accidental actions caused by helicopters (1) If the roof of a building has been designated as a landing pad for helicopters, a heavy emergency landing force should be considered, the vertical static equivalent design force being equal to: F d = A m (4.3) where: A is 100 kn ton -0.5 ; m is the mass, in tons. (2) The force due to impact should be considered to act on any part of the landing pad as well as on the roof structure within a maximum distance of 7 m from the edge of the landing pad. The area of impact may be taken as 2 2 m 2.

26 Page 26 Section 5 Explosions 5.1 Field of application (1)P Design situations classified as Category 1 : No specific consideration of the effects of an explosion is necessary other than complying with the rules for connections and interaction between components provided in ENV 1992 to ENV (2)P Design situations classified as Category 2 or 3 : key elements of the structure shall be designed to resist actions either using analysis based upon equivalent static load models or by applying prescriptive design/detailing rules. (3) For structures in Category 3 it is recommended to consider the use of dynamic analysis as described in Annex B. 5.2 Representation of actions (1) In this context an explosion is defined as a rapid chemical reaction of dust or gas in air. It results in high temperatures and high overpressures. Explosion pressures propagate as pressure waves. (2) The pressure generated by an internal explosion depends primarily on the type of gas or dust, the percentage of gas or dust in the air and the uniformity of gas or dust air mixture, the size and shape of the enclosure in which the explosion occurs, and the amount of venting or pressure release that may be available. NOTE: In completely closed rooms with infinitely strong walls, gas explosions may lead to pressures up to kn/m² and dust explosions up to kn/m², depending on the type of gas or dust. In practice, pressures generated are much lower due to imperfect mixing and the venting which occurs due to failure of doors, windows, etc. (3) To reduce confined explosion pressures and to limit the consequences of explosions the following guidelines may be applied : use of venting panels with defined venting pressures; separation of sections of the structure with explosion risks from other sections; limiting the area of sections with explosion risks; dedicated protective measures between sections with explosion risks from other sections to avoid explosion and pressure propagation. 5.3 Explosions in rooms with venting panels (1) Generally, there are many variable or unknown parameters, some outside the designer s control, making the effective estimating and modeling of the effects of an explosion complex and inexact.

27 Page 27 (2) In Category 2, for a single room event, an equivalent static load model analysis of key elements of a structure may be carried out using either the procedures described in 5.3(3) or 5.3(4). (3) Each key element and its connections should be designed to withstand a notional accidental static pressure of design value p d = 20 kn/m², applied from any direction, together with any reaction which could be expected to be directly transmitted to the member by an attached building component which is also subjected to the same pressure. (4) Key elements are designed to withstand the effects of an internal natural gas explosion using a nominal equivalent static pressure given by: or p d = 3 + p v (5.1) p d = 3 + p v /2+0,04/(A v /V)² (5.2) whichever is the greater, where: p v A v V is the uniformly distributed static pressure at which venting components will fail, in (kn/m²); is the area of venting components, in square metres; is the volume of room, in cubic metres. The ratio of the area of venting components and the volume are valid as in (5.3): 0,05 (1/m) A v /V 0,15 (1/m) (5.3) The expressions (5.1) and (5.2) are valid in a room up to m³ total volume. The explosive pressure acts effectively simultaneously on all of the bounding surfaces of the room. NOTE 1: Where building components with different p v values contribute to the venting area, the largest value of p v is to be used. (5) Paragraphs 5.3.(3) and 5.3.(4) apply to buildings which have provision of natural gas or which may have this provision in future, on the basis of which a natural gas explosion may be considered the normative design accidental situation. For design of buildings where provision of natural gas is totally impossible, a reduced value of the equivalent static pressure p d may be appropriate. Key elements should have adequate robustness to resist other design accidental situations, see Section 3.

28 Page 28 Annex A (Informative) Advanced impact design A.1 General (1) Advanced design for accidental actions due to impact may include one or several of the following aspects: dynamic effects; non-linear material behaviour; probabilistic aspects; analysis of consequences; economic optimisation of mitigating measures. (2) In the absence of quantification of consequences and economical optimisation, a failure probability of 10-4 per year seems to be appropriate for accidental actions. NOTE: For variable actions the exceedance probability, according to ENV is Φ(-αβ) = Φ(-0,7 3,8) = Φ(-2,7) = 0,003 for a reference period of 50 years. This corresponds to a probability of 0, per year. A.2 Impact dynamics (1) Impact is an interaction phenomenon between the object and the structure. To find the forces at the interface, object and structure should be considered as one integrated system. (2) Approximations, of course, are possible, for instance by assuming that the structure is rigid and immovable and the colliding object can be modelled as a equivalent elastic continuous rod (see figure A.1). In that case the maximum resulting interaction force and the duration of the loading are given by: F = vr k m (A.1) t = m/ k (A.2) where: v r k m l A E ρ is the object velocity at impact; is the equivalent elastic stiffness of the object = EA/l; is the mass of colliding object = ρal; is the length of the rod; is the cross sectional area; is the module of elasticity; is the mass density of the rod.

29 Page 29 The shape of the force due to impact is a block function; if relevant a rise time can be applied (see Figure A.1). (3) Expression (A.1) gives the maximum force value on the outer surface of the structure. Inside the structure these forces may give rise to dynamic effects. An upperbound for these effects can be found if the structure is assumed to behave elastically and the load is conceived as a step function. In that case the dynamic amplification factor ϕ dyn is 2,0. If the pulse nature of the load is taken into account, calculations will lead to amplification factors ϕ dyn ranging from below 1,0 up to 1,8, depending on the dynamic characteristics of the structure and the object. However, in general, it is recommended to use non-linear dynamic analysis to determine with the loads specified in this annex. Figure A.1 : Impact model A.3 Impact from trucks and lorries (1) In the absence of a detailed analysis the probability of a structural element being approached by a truck or lorry which has left its lane may be assumed to be 0,01 per year. The target failure probability for a structural element, given a truck or lorry approaching in its direction, therefore is 10-4 /10-2 = 0,01. (2) Given a truck or lorry approaching a structural element and the target failure probability according to A.3.(1) the design force F d may be derived from: ( ( r )) P mk v 2 2as > Fd 001 =, (A.3) where: a s is the deceleration of the truck after leaving the track; is the distance from the point where the truck leaves its track to the structural element, see Figure 4.1. For the other variables, see (A.1) and (A.2).

30 Page 30 Notional probabilistic information for the basic variables partly based on statistical data and partly on engineering judgement is given in Table A.1. (3) Based on the data and targets in this section the following design value for the force due to impact can be determined: F = F 1 s/ s (A.4) d 0 br where: F 0 s br is the collision force is the braking distance. Values are presented in Table A.2. This table also presents the design values for m and v. A deviation from the lane direction of 30 degrees may be adopted for the truck or lorry after braking. (4) In the absence of a dynamic analysis the dynamic amplification for the elastic response may be put equal to 1,4. Table A.1 : Notional data for probabilistic collision force calculation variable designation probability distribution v vehicle velocity -highway lognormal -urban area lognormal -courtyard lognormal -parking house lognormal mean value 80 (km/h) 40 (km/h) 15 (km/h) 5 (km/h) standard deviation 10 (km/h) 8 (km/h) 5 (km/h) 5 (km/h) a deceleration lognormal 4 (m 2 /s) 1,3 (m/s 2 ) m vehicle mass truck normal 20 (ton) 12 (ton) m vehicle mass car (kg) - k vehicle stiffness deterministic 300 (kn/m) -

31 Table A.2 : Design values for mass, velocity and collision force F 0 Page 31 type of road collision force braking mass m velocity v deceleration a based on (A.1) F 0 distance s br (kg) (km/h) (m/s 2 ) (kn) (m) motorway urban area courtyards only passenger cars also trucks parking garages only passenger cars NOTE: The values in this table are significantly higher than the values in Table 4.1 of the main text; if, however, the structure is analysed using non-linear dynamic models, the required structural dimensions will often be of the same order. 5 5

32 Page 32 A.4 Impact by trains (1) Reference is made to UIC SC 7J report 777/2 R (May 1996) with title : STRUCTURES BUILT OVER RAILWAY LINES (Construction requirements in the track zone) A.5 Impact by ships (1) If data about types of ships, traffic intensities, error probability rates and sailing velocities are known, a design force F d may be found from (see Figure A.2): PF ( F)= nt(1- p ) λ( xpv ) [ ( xy, ) ( km) > F ] f ( y)dxdy = 10 4 Erreur! Les arguments du com > d a r d s where: v r (x,y) k m n T p a λ f s (y) is the impact velocity of the ship, given error or mechanical failure at point (x,y); is the equivalent stiffness of the ship; is the mass of the ship; is the number of ships per time unit (traffic intensity); is the reference period (1 year); is the probability that a collision is avoided by human intervention; is the probability of a failure per unit travelling distance; is the distribution of initial ship position in y direction. (2) As an approximation for expression (A.5) F d may be derived from expression (A.1). In elaborating expression (A.1) it is recommended to use the medium mass value for the relevant ship class defined in Table 4.3 of the main text, a design velocity v rd equal to 3 m/s increased by the water velocity and k = 15 MN/m for sea going vessels and k = 5 MN/m for inland ships. In harbours the velocity may be assumed as 1,5 m/s and at full sea 5 m/s is recommended. (3) The load duration may be derived from expression (A.2). For cases where the rise time is relevant this may be assumed as u e /v rd, where u e is the elastic deformation for which a value of 0,1 m may be taken. (4) In the absence of a dynamic analysis, a frontal impact factor of 1,3 and a lateral impact factor of 1,7 is recommended.

33 Page 33 B Figure A.2 : y Ship collision scenario

34 Page 34 Annex B (informative) Explosions B.1 General (1) Advanced design for explosions may include one or several of the following aspects: explosion pressure calculations, including the effects of confinements and breaking panels; dynamic non linear structural calculations; probabilistic aspects and analysis of consequences; economic optimisation of mitigating measures. (2) In the absence of quantification of consequences and economical optimisation, a failure probability of 10-4 per year seems to be appropriate for accidental actions. NOTE: For variable actions the exceedance probability, according to ENV , is Φ(-αβ) = Φ(-0,7 3,8) = Φ(-2,7) = 0,003 for a reference period of 50 years. This corresponds to a probability of 0, per year. B.2 Structures in category 3 (1) Critical locations where explosions might be initiated should be considered. Explosion pressures on the structural elements should be estimated taking into account, as appropriate, reactions transmitted to the structural elements by non-structural elements. Due allowance should be made for probable dissipation of gas throughout the building, for venting effects, for the geometry of the room or group of rooms under consideration etc. Elements which are not key elements may fail; key elements may be damaged so long as they retain their structural integrity. It is recommended that propane gas be considered for design purposes unless the probability is acceptably low that such gas could ever be present within the building. (2) The estimated peak pressures may be higher than the values presented in the main text of this Part, but these can be considered in the context of a maximum load duration of 0,2 s and plastic ductile material behaviour (assuming appropriate detailing of connections to ensure ductile behaviour). B.3 Dust explosions (1) The type of dust under normal circumstances may be considered by a material parameter K St, which characterises the confined explosion behaviour. K St may be experimentally determined by standard methods for each type of dust. A higher value for K St lead to higher pressures and shorter rise times for internal explosion pressures. The value of K St depends on factors such as changes in the chemical composition, particle size and moisture content. The values for K St given in Table B.1 are examples.