Dr-Ing. Nikolaos E. Malakatas Eurocode 1: Actions on structures – Part 1-1: General actions – Accidental actions Dr-Ing. Nikolaos E. Malakatas Director of Design and Studies of Road Projects Ministry of Infrastructures, Transports and Networks - GREECE Chairman of CEN/TC250/SC1

Eurocode EN 1991-1-7 1. General 2. Classification 3. Design situations   1. General 2. Classification 3. Design situations 4. Impact 5. Explosions Annexes Design for localised failure Risk analysis C. Dynamics D. Explosions

EN 1990 Section 2.1 Basic Requirements (4)P A structure shall be designed and executed in such a way that it will not be damaged by events like - explosion - impact and - consequences of human errors to an extent disproportionate to the original cause Note: Further information is given in EN 1991-1-7

EN 1990 guidance: reducing hazards low sensitive structural form survival of local damage sufficient warning at collapse tying members

Definitions from EN 1990 Accidental action An action, usually of short duration, but of significant magnitude, that is unlikely to occur on a given structure during the design working life. Note: An accidental action can be expected in many cases to cause severe consequences unless appropriate measures are taken. Progressive collapse A chain reaction of failures following damage to a relatively small portion of a structure. The damage resulting from progressive collapse is disproportionate to the damage that initiated the collapse. Robustness The ability of a structure to withstand events like fire, explosions, impact or the consequences of human error, without being damaged to an extent disproportionate to the original cause.

Ronan Point - 1968

Piped Gas – very severe explosions

Vehicle Impacts Very Severe

World Trade Center USA, 2001

Design strategies

Strategies for Identified Accidental Design Situations In the design of a structure, design situations involving identified accidental actions are considered with account taken of: the measures taken for preventing or reducing the risk from the accidental action; the probability of occurrence of the identified accidental action; the consequences of the identified accidental action ; the level of acceptable risk.

Strategies for limiting the extent of Localised Failure Consideration should be given to minimising the potential damage to the structure arising from an unspecified cause, taking into account its use and exposure, by adopting one or more of the following strategies. designing the structure with enhanced redundancy so that neither the whole structure nor a significant part of it will collapse if a local failure (e.g. single element failure or damage) occurs; designing key elements, on which the structure is particularly reliant, to sustain a notional accidental action Ad; applying prescriptive design/detailing rules that provide acceptable robustness for the structure (e.g. three-dimensional tying for additional integrity, or minimum level of ductility of structural elements subject to impact).

Accidental Actions and Hazards on Structures

Impact on walls and supporting structures

Annex B: scenario model

Annex C: force model F=v(km) model and experiment

Design example: Bridge column in motorway

Resistance: Bending moment: MRdx = 0.8  h2 b fy = 0.8 0.01 1.002 0.50 300 000 = 1200 kNm > 940 kNm  

Impacts from vehicles on building and bridge superstructures Recommended minimum equivalent static design forces due to impact on members of the bridge superstructure Category Minimum Force Fd,x a [kN]   Motorways and country national roads 500 Country Roads in rural area 375 Roads in Urban area 250 Court yards and parking garages 75 a x = direction of normal travel to the direction of normal travel. These values for Fd,x are applicable for h  h0 (h0 is given in the National Annex – EN 1991-1-7 recommended value is 5 m)

Impacts from vehicles on U/S of buildings and on bridge superstructure Reduction factor r for impact force F on members of superstructure depending on free height [h0 ≤ h ≤ (h0 + b)] rF : reduction coefficient Indicative values : b = 1,0 m h0 = 5,0 m h1 = 6,0 m

IMPACT FROM SHIPS - Ship characteristics and dynamic design forces due to ship impact on inland waterways CEMTa Class Reference type of ship Length  (m) Mass m (ton) b Force Fdx c (kN) Force Fd yc I 30-50 200-400 2 000 1 000 II 50-60 400-650 3 000 1 500 III “Gustav König” 60-80 650-1 000 4 000 IV Class „Europe“ 80-90 1 000-1 500 5 000 2 500 Va Big ship 90-110 1 500-3 000 8 000 3 500 Vb Tow + 2 barges 110-180 3 000-6 000 10 000 Vla Vlb Tow + 4 barges 110-190 6 000-12 000 14 000 Vlc Tow + 6 barges 190-280 10 000-18 000 17 000 VII Tow + 9 barges 300 14 000-27 000 20 000 aCEMT: European Conference of Ministers of Transport, classification proposed 19 June 1992, approved by the Council of European Union, 29 October 1993.

Ship Impact for Sea Watres Class of ship Length = (m) Mass ma (ton) Force Fd xb,c (kN) Force Fd y b, c Small 50 3 000 30 000 15 000 Medium 100 10 000 80 000 40 000 Large 200 240 000 120 000 Very large 300 100 000 460 000 230 000 a The mass m in tons (1ton = 1000kg) includes the total mass of the vessel, including the ship structure, the cargo and the fuel. It is often referred to as the displacement tonnage. It does not include the added hydraulic mass. b The forces given correspond to a velocity of about 5,0 m/s. They include the effects of added hydraulic mass. c Where relevant the effect of bulbs should be accounted for.

Impact from sea going vessels The point of impact is applicable between - 0,05L and + 0,05L above the design water levels. The area of impact is 0,05L height and 0,1L width. In harbour areas the forces may be reduced by 2. In the absence of a dynamic analysis dynamic amplification factors should be applied. Indicative values are 1,3 for frontal impact and 1,7 for lateral conditions of impact.

Impacts from derailed rail traffic Classes of structures subject to impact from derailed traffic Class A - Structures that span across or near to the operational railway that are either permanently occupied or serve as a temporary gathering place for people or consist of more than one storey. Class B - Massive structures that span across the operational railway such as bridges carrying vehicular traffic or single storey buildings that are not permanently occupied or do not serve as a temporary gathering place for people. (Guidance in National Annex or for Individual Project)

x is the track direction y is perpendicular to track direction Class A Structures - Recommended horizontal static equivalent design forces due to impact or alongside railways Distance “d” from structural elements to the centreline of the nearest track (m) Force Fdx (kN) x is the track direction Force Fdy (kN) y is perpendicular to track direction d < 3 m To be specified for the individual project. Further information is set out in Annex B 3 m  d  5 m 4,000 1,500 d > 5 m

Impacts from Fork Lift Trucks EN 1991-1-7 gives information on Accidental Actions caused by Fork lift trucks The equivalent accidental design force F, should determined according to advanced impact design for soft impact.. Alternatively, F may be taken as F = 5W, where W is the sum of the net weight and hoisting load of a loaded truck applied at a height of 0,75 m above floor level depending on the local situation higher or lower values may be more appropriate.

Accidental actions caused by helicopters For roofs of a building, designated as a landing pad for helicopters, a heavy emergency landing force Fd (a vertical static equivalent design force) should be taken into account. Fd = C(m)0,5 where: C is 3 kN [kg-0.5 ] m is the mass of the helicopter [kg]. 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 m  2 m.

Internal Explosions EN 1991-1-7 defines actions due to internal explosions due to. dust explosions in rooms, vessels and bunkers ; natural gas explosions in rooms; gas and vapour/air explosions in road and rail tunnels. The influence on the magnitude of an explosion of several connected rooms filled with explosive dust, gas or vapour is not treated in EN 1991-1-7. Principles of Design to resist progressive collapse : Structural elements may be allowed to fail provided they are not key elements and do not result in overall collapse or loss of structural integrity of the structure

Internal Explosions – Principles of Design to resist progressive collapse To reduce confined explosion pressures and to limit the consequences of explosions the following guidelines are given by EN 1991-1-7 design the structure to resist the maximum explosion overpressure; use venting panels with defined venting pressures; separate adjacent sections of the structure containing explosive material; limit the area of structures exposed to explosion risks; provide dedicated protective measures between adjacent structures exposed to explosion risks to avoid pressure propagation.

Internal Explosions – Advanced Design For advanced design for explosions EN 1991-1-7 specifies the use of one or several of the following aspects: explosion pressure calculations, including the effects of confinements and venting panels ; dynamic non linear structural calculations ; probabilistic aspects and analysis of consequences ; economic optimisation of mitigating measures.

INTERNAL NATURAL GAS EXPLOSIONS The design pressure is the maximum of: pd = 3 + pv pd = 3 + 0.5 pv+0,04/(Av/V)2 pd = nominal equivalent static pressure [kN/m2] Av = area of venting components [m2] V = volume of room [m3] Validity: V < 1000 m3 ; 0,05 m-1 < Av / V < 0,15 m-1 Annex B: load duration = 0.2 s

Design Example: Compartment in a multi story building Compartment: 3 x 8 x 14 m Two glass walls (pv =3 kN/m2) and two concrete walls

explosion pressure: pEd = 3 + pv/2 + 0,04/(Av/V)2 = 3 + 1.5 + 0.04 / 0.1442 = 6.5 kN/m2 self weight = 3.0 kN/m2 live load = 2.0 kN/m2 Design load combination (bottom floor): pda = pSW + pE + 1LL pLL = 3.00 + 6.50 + 0.5*2.00 = 10.50 kN/m2

Be careful for upper floors and columns

Dynamic increase in load carrying capacity t = 0.2 s = load duration g = 10 m/s2 umax = 0.20 m = midspan deflection at collapse psw = 3,0 kN/m2 and pRd =7.7 kN/m2 pREd = d pRd = 1.6 * 7.7 = 12.5 kN/m2 > 10.5 kN/m2 Conclusion: bottom floor system okay

Annex A: Classification of buildings

Annex A: Measures to be taken

Class 2a (lower group)

Class 2a (lower group) Ti= 0.8 (gk+ qk)sL = 0.8{3+0.5*3}x4x5=88 kN>75 kN FeB 500: A = 202 mm2 or 2 Ø12mm

Example structure, Class 2, Upper Group, Framed   L =7.2 m, s =6 m, qk=gk=4 kN/m2, =1.0

Example structure   Internal horizontal tie force Ti = 0.8 (gk +  qk) s L = 0.8 {4+4} (6 x 7.2) = 276 kN FeB 500: A = 550 mm2 or 2 ø18 mm. Vertical tying force: Ti = (gk +  qk) s L = {4+4} (6 x 7.2) = 350 kN FeB 500: A = 700 mm2 or 3 ø18 mm.

Class 2 higher class – walls

Class 2 higher class – walls Tyings Horizontal: Ti = Ft (gk + yqk) /7,5 × z/5 kN/m > Ft Periphery: Tp= Ft Vertical: T = 34 A / 8000 × (H/t)² in N > 100 kN/m Ft = 20 + 4ns kN/m < 60 kN/m ns = number of storeys z = span A = horizontal cross section of wall [mm²] H = free storey height t = wall thickness

Class 2 higher class – walls Design Example: L = 7,2 m, H = 2,8 m en t = 250 mm T = 34×7200×250/8000 × (2800/250)² = = 960 ×10³ N = 960 kN > 720 kN maximal distance 5 m maximal distance from edge: 2.5 m Result: 2 tyings of 480 kN

Effect of tyings in walls

Guidance can be found in Annex B: Class 3: Risk analysis Guidance can be found in Annex B:

Points of attention in risk analysis list of hazards irregular structural shapes new construction types or materials number of potential casualties strategic role (lifelines)

Step 1: identification of hazard Hi Step 2: damage Dj at given hazard  Risk calculation:   Step 1: identification of hazard Hi Step 2: damage Dj at given hazard Step 3: structural behavour Sk and cpmsequences C(Sk)   Take sum over all hazards and damage types

Annex C - Dynamic design for impact Impact dynamics Hard Impact, where the impact is mainly dissipated by the impacting body Soft Impact, where the structure is designed to deform in order to absorb the impact energy Annex C gives advanced design methods to determine considering the interaction between the moving object and a structure Impact from aberrant road vehicles Impact by ships Impact by river and canal traffic Impact by seagoing vessels

gas explosions in buildings Annex D: gas explosions in buildings gas explosions in tunnels dust explosions

Annex D - Internal explosions Dust explosions in rooms, vessels and bunkers Natural gas explosions Explosions in road and rail tunnels

THANK YOU FOR YOUR ATTENTION