Table E-1 F-Scale Classification of Tornadoes Based on Damage (Ref. E-2)

DOE-STD-1020-2002

document are based on F-Scale wind speeds at 33 ft (10 meters) above ground in flat open

country.

Table E-1 F-Scale Classification of Tornadoes Based on Damage (Ref. E-2)

LIGHT DAMAGE 40-72 mph (peak gust wind speed)

(F0)

Some damage to chimneys or TV antennae; breaks branches off trees; pushes over shallow

rooted trees; old trees with hollow insides break or fall; sign boards damaged.

MODERATE DAMAGE 73-112 mph (peak gust wind speed)

(F1)

73 mph is the beginning of hurricane wind speed. Peels surface off roofs; windows broken; trailer

houses pushed or overturned; trees on soft ground uprooted; some trees snapped; moving autos

pushed off the road.

CONSIDERABLE DAMAGE 113-157 mph (peak gust wind speed)

Roof torn off frame houses leaving strong upright wall standing; weak structure or outbuildings

(F2)

demolished; trailer houses demolished; railroad boxcars pushed over; large trees snapped or

uprooted; light-object missiles generated; cars blow off highway; block structures and walls badly

damaged.

SEVERE DAMAGE 158-206 mph (peak gust wind speed)

Roofs and some walls torn off well-constructed frame houses; some rural buildings completely

(F3)

demolished or flattened; trains overturned; steel framed hanger-warehouse type structures torn;

cars lifted off the ground and may roll some distance; most trees in a forest uprooted, snapped,

or leveled; block structures often leveled.

DEVASTATING DAMAGE 207-260 mph (peak gust wind speed)

Well-constructed frame houses leveled, leaving piles of debris; structure with weak foundation

(F4)

lifted, torn, and blown off some distance; trees debarked by small flying debris; sand soil eroded

and gravels fly in high winds; cars thrown some distances or rolled considerable distance finally

to disintegrate; large missiles generated.

INCREDIBLE DAMAGE 261-318 mph (peak gust wind speed)

(F5)

Strong frame houses lifted clear off foundation and carried considerable distance to disintegrate;

steel-reinforced concrete structures badly damaged; automobile-sized missiles carried a distance

of 100 yards or more; trees debarked completely; incredible phenomena can occur.

E-2.1 Wind Pressures

Wind pressures on structures (buildings) can be classified as external or internal.

External pressures develop as air flows over and around enclosed structures. The air particles

change speed and direction, which produces a variation of pressure on the external surfaces of

the structure. At sharp edges, the air particles separate from contact with the building surface,

with an attendant energy loss. These particles produce large outward-acting pressures near the

location where the separation takes place. External pressures act outward on all surfaces of an

E-5