STOCHASTIC DESCRIPTION OF TURBULENT WIND - Theory of Bridge Aerodynamics - page 55

2

⎡ ⎤

V

1

⎛ ⎞

( ) ( )

s

PV V 1 PV V exp

⎢ ⎥

μ = > = − ≤ = −

⎜ ⎟ r r s r r s

2 V

⎢ ⎥

(3.4)

⎝ ⎠ m

⎣ ⎦

VV 2ln

⇒ = − μ

s m

V is then

Taken from the entire population of observations, independent of direction,

the velocity that has a probability of being exceeded.

μ

Fig. 3.2 The probability density distribution of the mean wind velocity

μ , V may be interpreted as what can be expected to be
representative under severe weather conditions on the site. However, this is usually not
considered the appropriate procedure for singling out a characteristic mean wind velocity
for design checks against ultimate structural failure. For the purpose of structural design,
the mean wind velocity that corresponds to an extreme weather condition with a certain
small probability of occurrence is rather based on a limited data set of annual maxima,
V , as illustrated on the right hand side of Fig. 3.2. This data is usually dealt with in the
form of the mean wind velocity pressure

For a suitably small value of

2 / 2

q

V and fitted to a Fischer - Tippet = ρ

Type I distribution

q ⎡ ⎛ − α ⎞ ⎤

( )

V

Pq q exp exp ≤= − −

⎦ (3.5)

⎢ ⎜ ⎟ ⎥

aV V

a

β

⎣ ⎝ ⎠