1. 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

2. 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

3. 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

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

5. 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.

6. Ronan Point

7. Piped Gas – very severe explosions

8. Vehicle Impacts
Very Severe

9. World Trade Center
USA, 2001

10. Design strategies

11. 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.

12. 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).

13. Accidental Actions and Hazards on Structures

14. Impact on walls and supporting structures

15. Annex B: scenario model

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

18. Design example: Bridge column in motorway

19. Resistance: Bending moment: MRdx = 0.8  h2 b fy=
= 1200 kNm > 940 kNm

20. 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 recommended value is 5 m)

21. 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

22. 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
2 000
1 000 II
50-60
3 000
1 500
III
“Gustav König”
60-80
4 000 IV
Class „Europe“
80-90
5 000
2 500 Va
Big ship
90-110
8 000
3 500 Vb
Tow + 2 barges
10 000
Vla
Vlb
Tow + 4 barges
14 000
Vlc
Tow + 6 barges
17 000
VII
Tow + 9 barges
300
20 000
aCEMT: European Conference of Ministers of Transport, classification proposed 19 June 1992, approved by
the Council of European Union, 29 October 1993.

23. 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
Very large
300
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.

24. 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.

25. 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)

26. 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

27. Impacts from Fork Lift Trucks
EN 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.

28. 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.

29. Internal Explosions
EN 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
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

30. 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
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.

31. Internal Explosions – Advanced Design
For advanced design for explosions EN 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.

32. INTERNAL NATURAL GAS EXPLOSIONS
The design pressure is the maximum of:
pd = 3 + pv
pd = 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

33. 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

34. explosion pressure:
pEd = 3 + pv/2 + 0,04/(Av/V)2
= / = 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
= *2.00 = kN/m2

35. Be careful for upper floors and columns

36. 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

37. Annex A: Classification of buildings

38. Annex A: Measures to be taken

39. Class 2a (lower group)

40. 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

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

42. 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.

43. Class 2 higher class – walls

44. 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 = ns 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

45. 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

46. Effect of tyings in walls

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

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

50. 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

51. 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

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

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

54. THANK YOU FOR YOUR ATTENTION