extreme wind and snow loads for structural design
TRANSCRIPT
Extreme Wind and Snow loads for structural design
WG 4 Meeting in Delft, 17-18 November 2006
D. LunguC. Arion
COST Action C26Urban habitat constructions under catastrophic events
Technical University of
Civil Engineering
Bucharest
WG 4 Meeting in Delft, 17-18 November 2006
WG 4 Meeting in Delft, 17-18 November 2006
The meteorological database comprises the maximum annual wind velocity (at 10 m, averaged on 1 min) at more than
140 National Institute of Meteorology and Hydrology locations in Romania, at which wind speed measurements were made.
The period of records for these locations is between 20 to 60 years, up through the 2005.
Wind action in Romania
WG 4 Meeting in Delft, 17-18 November 2006
The extreme value distribution used for the estimation of the characteristic wind velocity is the Gumbel distribution for maxima.
The coefficient of variation of the maximum annual wind velocity is in the range VU = 0.15÷0.3 with mean 0.23 and standard deviation 0.06.
Romanian Code for Wind Loads, 2004 was prepared by UTCB.
WG 4 Meeting in Delft, 17-18 November 2006
Romania – Meteorological database of wind record (example)
T=25ani T=50ani T=100ani1 Adamclisi 27 24 17 0.21 0.37 25 27 29
2 Adjud 27 40 22 0.21 2.58 31 34 36
3 Alexandria 27 40 26 0.29 0.81 41 45 49
4 Apa Neagra 27 17 11 0.28 0.39 18 20 21
5 Avrameni 27 40 25 0.19 1.22 35 37 40
6 Bacau 27 40 18 0.35 1.73 32 35 39
Viteza caracteristica (m/s)
Coef.asim.NR STATIA
Nr.ani Viteza max (m/s)
Viteza medie (m/s)
Coef.var.
PARAMETRII DE VANT
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0 0.1 0.2 0.3 0.4 0.5
Coefficient of variation
Rel
ativ
e fre
quen
cy Maximum annual wind speed
Mean 0.23
Cov 0.26
WG 4 Meeting in Delft, 17-18 November 2006
Romania – Maximum recorded wind velocity
WG 4 Meeting in Delft, 17-18 November 2006
Romania - Characteristic wind velocity averaged on 1 min having 2% annual probability to be exceeded
WG 4 Meeting in Delft, 17-18 November 2006
WG 4 Meeting in Delft, 17-18 November 2006
WG 4 Meeting in Delft, 17-18 November 2006
Test site – Tg. Jiu (Romania)The statistical indicators for the maximum annual wind velocity averaged on 1 min in Tg. Jiu are as follows:
- Maximum observed wind velocity, 35 m/s- Mean of the annual maxima, 17 m/s- Standard deviation, 5.1 m/s- Coefficient of variation, 0.30 - Skewness coefficient, 1.65.
34 m/s100 yr
31m/s50 yr
28 m/s10 yr
Wind velocity in Gumbel largest extreme distribution
Mean recurrence interval
1min mean wind velocity at 10meters abovethe ground in Tg. Jiu
= 0.83⋅ 31 = 25.7 m/s = Vref
min1050 yrTV =
The statistic indicators for maximum annual wind velocity averaged on 10 min in Tg. Jiu are:
m1 = 0.83⋅17m/s = 14.5 m/sσ1 = 4.35 m/s (since V1 = 0.3).
11N 282.1Nln
mm σ⋅+=
1
1
11
1
N
NN
V282.1Nln1
V
282.1Nlnmm
V⋅+
=⋅+
==σ
σσ
σN = σ1
the mean, standard deviation and coefficient of variation of maximum wind velocity in N years in Gumbel distribution
WG 4 Meeting in Delft, 17-18 November 2006
Wind turbulence
POWER SPECTRAL DENSITIES FOR ALONG-WIND GUSTINESS
Karman (1948), Panovski (1964), Davenport (1967), Harris (1968), Flicht (1970), Kaimal (1972), Simiu (1974,1975), ESDU (1976, 1985), Naito (1978, 1983), Kareem (1985), Solari (1987,1993).
Solari and von Karman spectral densities are compared.
WG 4 Meeting in Delft, 17-18 November 2006
x=Lu n / V(z)where Lu is eitherLu
C=300(z/300)0.46+0.074lnz0 orLu
old_ESDU =25z0.35z0-0.063
x=LuC n / V(z),
where:Lu
C=300(z/300)0.46+0.074lnz0
von Karman inJCSS and CIB codes
Solari inEurocode 1
Power spectra of the along-wind gust velocity
nGu(n)/σu2 is the normalized spectrum (i.e. unit area)
n the frequency in HzV(z) the mean velocity at height z
u
u2 5
3
nG (n)=
6.868x
(1+10.32x )σu
u2
256
nG (n)=
4x
(1+ 70.8 x )σ
WG 4 Meeting in Delft, 17-18 November 2006
Lu is the integral length scale (after Couniham or ESDU)
0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 00
5 0
1 0 0
1 5 0
2 0 0
2 5 0
3 0 0
z [m ]
Inte
gral
leng
th s
cale
C o un iha m a nd E S D U in te g ra l le ng th s c a le s
C o un iha m
O ld _ E S D U
WG 4 Meeting in Delft, 17-18 November 2006
10-1
100
101
102
0
0.1
Frequency [Hz]
Nor
mal
ized
spe
ctru
m
vref=30m/s, z0=0.05m, z=10m
10-2
100
0
0.2
Frequency [Hz]
Nor
mal
ized
spe
ctru
m
vref=30m/s, z0=0.05m, z=100
10-1
100
101
102
0
0.1
0.2
Frequency [Hz]
Nor
mal
ized
spe
ctru
m
vref=30m/s, z0=0.3m, z=10m
10-2
100
0
0.2
Frequency [Hz]
Nor
mal
ized
spe
ctru
m
vref=30m/s, z0=0.3m, z=100
Solari spectrum with Couniham integral length scale (SC), the Von Karman spectrum with Couniham integral length scale (KC),the von Karman spectrum with old ESDU integral length scale (KE).
For every combination of input values (Vref=30m/s, z0=0.05..0.3m, and z=10..100m), the same ordering in spectra
is found (from high to low): KE, SC, KC.
van Gelder & Lungu, 1998
WG 4 Meeting in Delft, 17-18 November 2006
Comparison between various spectral densities over the whole frequency range at z=100m, vref=30m/s and z0=0.05m.
1 0-4
1 0-2
1 00
0
0 .0 5
0 .1
0 .1 5
0 .2
0 .2 5
0 .3
F r e q u e n c y [H z ]
Nor
mal
ized
spe
ctru
m
v r e f= 3 0 m /s ; z 0 = 0 .0 5 m ; z = 1 0 0 m
Solari spectrum with Couniham integral length scale (SC), the Von Karman spectrum with Couniham integral length scale (KC),the von Karman spectrum with old ESDU integral length scale (KE).
van Gelder & Lungu, 1998
WG 4 Meeting in Delft, 17-18 November 2006
The meteorological database comprises the maximum annual snow height and water equivalence at more than
110 National Institute of Meteorology and Hydrology locations in Romania, at which the measurements were made.
The period of records for these locations is between 20 to 60 years, up through the 2005.
Snow action in Romania
WG 4 Meeting in Delft, 17-18 November 2006
The distribution used for the estimation of the characteristic snow load is the lognormal distribution for maxima.
The coefficient of variation of the maximum annual snow weight has the mean value VU = 0.57 and maximum value close to 1.
Romanian Code for Snow Loads, 2005 was prepared by UTCB.
WG 4 Meeting in Delft, 17-18 November 2006
0
0.05
0.1
0.15
0.2
0.25
0 0.2 0.4 0.6 0.8 1 1.2 1.4
Coefficient of variation
Rel
ativ
e fre
quen
cy
Maximum annual ground snow119 meteo stations
Mean 0.57Cov 0.25
WG 4 Meeting in Delft, 17-18 November 2006
Romania - Characteristic snow load s0,k , kN/m2
WG 4 Meeting in Delft, 17-18 November 2006
( ) ( )2V1ln054.2C
k,0
N ess +⋅−=
0.6
0.7
0.8
0.9
1.0
1.1
1.2
10 20 30 40 50 60 70 80 90 100
Interval mediu de recurenta IMR , ani
s N/s
0,k
V=0,1V=0,3V=0,5V=0,7
2.326100
2.05450
1.75125
1.28210
CMean recurrence interval, MRI=N years
Ratio of characteristic values defined by variousrecurrence intervals (lognormal distribution)