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Class
Advanced Building Skins
Table 2: Explosion scenarios (vehicles bombs) of the ISO 16933, Annex C1 [4]
Peak
reflected
overpressure
p ˆ r
Reflected
Impulse
i r
Length of
overpressure
phase (linear)
- 4 -
Stand-off 100 kg
TNT in front of
small mockup
(3,15m x 3,15m)
Stand-off
[m]
Equivalent explosion
scenario in front of
large facade
0
t d,
lin
[kPa] [Pa s] [ms]
EXV 45 30 180 12 45 30
EXV 33 50 250 10 33 30
EXV 25 80 380 9,5 25 40
EXV 19 140 600 8,6 19 64
EXV 15 250 850 6,8 15 80
EXV 12 450 1200 5,3 12 100
EXV 10 800 1600 5,0 10 125
3 Safety Requirements for explosive Loads
Even slight pressure wave generated by small bombs or large bombs at a great distance (e.g. in a
neighboring street), can lead to major damage if the facade is not properly constructed. To protect
persons behind the facade from major injuries, an explosion-resistant function of the facade is
frequently specified. Most specifications refer to a classification of the performance condition
according to the US GSA standard [7]. The GSA method classifies facades into six protection and risk
classes (protection and hazard levels, Figure 2). For the highest protection class 1 the glass must not
break. In the other protection classes it is defined how far glass splinters are allowed to fly into a
standardized test box. Most commonly the protection class 3B is specified in which the splitters may
fly in maximum 10 ft. (3.05 m) into the test box.
The GSA protection classes are developed for window glazing spanning in maximum from floor to
ceiling. The direct use of the GSA protection classes would therefore be inappropriate for multi-story
high cable net facades. The key factors for the protection of individuals are: firstly, that the pressure
wave is considerably damped to protect ears and lungs and, secondly, that glass splinters do not act as
projectiles that cause heavy injuries. Therefore, a definition of the permitted flight distance of glass
splinters in relation to the height of the glazing would be more logical and could be used for all types
of facades. For numerical evidence, the speed of the glass splinters at the moment when the breaking
strength of the glass is reached could be defined as a protection class. For this method it needs to be
considered that the fracture stress significantly depends on the glass product and the load duration due
to the effects of the surface pre stress and the crack growth of flaws in the glass surface. For very short
impact loads, such as under explosions, much higher breakage strength is known compared to the
breakage strength for wind loads.
Figure 2: GSA/ISC performance conditions for window glazing according [7]
TNT
[kg]