Lifetime of buildingsChurches: 500yearsHarbor facilities: 200 yearsFamily houses: 100 yearsRoad bridges: 100 yearsRailway bridges: 80 yearsShopping malls: 80 yearsOffice buildings: 50 yearsIndustrial buildings: 40 years
What is the max, windspeed which is expected to occur once in the lifetime of the building?
wind statistics 2006 Bp.
0
5
10
15
20
25
30
0 2 4 6 8 10
wind speed m/s
annu
al p
roba
bilit
y %
Órás relatív szélirány- és szélsebességgyakoriság a Budapest, II. kerület, Kitaibel Pál u. OMSZ meteorológiai állomáson a 2005. évben
0
1
2
3
4
5É
ÉÉK
ÉK
KÉK
K
KDK
DK
DDK
D
DDNY
DNY
NYDNY
NY
NYÉNY
ÉNY
ÉÉNY0.0 - 0.5
0.5 - 1.0
1.0 - 1.5
1.5 - 2.0
2.0 - 2.5
2.5 - 3.0
3.0 - 3.5
3.5 - 4.0
4.0 - 4.5
4.5 - 5.0
Sebességosztályok [m/s]
H = 10 m
Gyakoriság [%]
Prediction of design wind speeds
• Return Period (mean recurrence interval) :
Unit : depends on population from which extreme value is selected
A 50-year return-period wind speed has an probability of exceedence of 0.02 in any one year
Return Period, R = exceedenceofyProbabilit1
(U)F11
U
e.g. for annual maximum wind speeds, R is in years
it should not be interpreted as occurring regularly every 50 years
or average rate of exceedence of 1 in 50 years
Wind loading and structural responseLecture 4 Dr. J.D. Holmes
Prediction of design wind speeds• Lifetime of structure, L
Appropriate return period, R, for a given risk of exceedence, r, during a lifetime ?
Assume each year is independent
L
R
)1(1
L
Rr
)1(11
)1(1R
Probability of non exceedence of a given wind speed
in any one year =
Probability of non exceedence of a given wind speed in L years =
Risk of exceedence of a given wind speed in L years,
Prediction of design wind speeds• Example :
L = 50 years
636.0)501(11
50
r
R = 50 years
There is a 64% chance that U50 will be exceeded in the next 50 years
Risk of exceedence of a 50-year return period wind speed in 50 years,
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 200 400 600
Mean reoccurence interval (MRI)
peak
gus
t win
d sp
eed
conv
ersi
on fa
ctor
MRI peak gust wind speed
years conversion factor
5 0.78
10 0.84
25 0.93
50 1
100 1.07
200 1.14
500 1.23
Ceppi, P., Della-Marta, P.M., Appenzeller, C.: 2008, Extreme Value Analysis of Wind Speed Observations over Switzerland, Arbeitsberichte der MeteoSchweiz, 219, 43pp
• T = 4 - 4.5 s link
William Jacobs: Building Periods: moving forward (and backward)STRUCTURE magazine June 2008