Upload
harish-ramachandran
View
50
Download
1
Tags:
Embed Size (px)
DESCRIPTION
Eurocode for Windload
Citation preview
Eurocode 1 Eurocode 1 - Actions on structures - - Actions on structures -
Part 1-4: General actionsPart 1-4: General actions
Wind actionsWind actions
Dr.-Ing. Gerhard ScheuermannDr.-Ing. Gerhard Scheuermann
CONTENTSCONTENTS
GeneralGeneral Design situationsDesign situations Wind velocity and velocity pressure Wind velocity and velocity pressure Wind actionsWind actions Structural factor cStructural factor css c cdd
Pressure and force coefficientsPressure and force coefficients Terrain effectsTerrain effects Procedures for determine the structural factor cProcedures for determine the structural factor css c cdd
Vortex shedding and aeroelastic instabilitiesVortex shedding and aeroelastic instabilities Dynamic characteristics of structuresDynamic characteristics of structures Wind Wind mapmap
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsGeneral General remarksremarks
National Annex (NA)National Annex (NA)
- - values/and or classes where alternatives are givenvalues/and or classes where alternatives are given
in the Eurocodesin the Eurocodes
- - values to be used where a symbol only is givenvalues to be used where a symbol only is given
- country specific data, e.g. snow map or a wind map- country specific data, e.g. snow map or a wind map
- the procedure to be used when alternative procedures are given- the procedure to be used when alternative procedures are given
- decisions on the application of Informative Annexes- decisions on the application of Informative Annexes
- reference to non-contradictory Annexes- reference to non-contradictory Annexes
EUROCODE 1 – Part 1-4: Wind actionsEUROCODE 1 – Part 1-4: Wind actionsGeneral remarksGeneral remarks
This part is applicable to buildings and civil engineering works This part is applicable to buildings and civil engineering works (land-based structures) with heights up to 200 m(land-based structures) with heights up to 200 m
Certain aspects necessary to determine wind actions on a structure Certain aspects necessary to determine wind actions on a structure need to be provided in the National Annex. Default values and need to be provided in the National Annex. Default values and methods are given in the main text, where the National Annex does methods are given in the main text, where the National Annex does not provide information.not provide information.
This part does not give guidance on local thermal effects on the This part does not give guidance on local thermal effects on the characteristic wind, e.g. strong arctic thermal surface inversion or characteristic wind, e.g. strong arctic thermal surface inversion or funnelling or tornadoes funnelling or tornadoes
This part does not give guidance on the following aspectsThis part does not give guidance on the following aspects– wind actions on lattice towers with non –parallel chordswind actions on lattice towers with non –parallel chords
– wind actions on guyed masts and guyed chimneys wind actions on guyed masts and guyed chimneys
– torsional vibrations, e.g. tall buildings with a central coretorsional vibrations, e.g. tall buildings with a central core
– vibrations where more than the fundamental mode needs to be vibrations where more than the fundamental mode needs to be considered. considered.
EN 1993-3-1
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsDesign Design situationssituations
The relevant wind actions shall be determined for each The relevant wind actions shall be determined for each design situation identified in accordance with EN 1990: design situation identified in accordance with EN 1990: Ultimate limit stateUltimate limit state
1 1 ,,0,
""1,1,
"""",,j i ik
QiiQk
PPjk
GjG
1 1 ,,2
""1,
)("""", 1,21,1
j i ikQik
QorAjk
G d
recommended values of factors for buildings:0 = 0,61 = 0,22 = 0,0
Q = 1,5
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsDesign Design situationssituations
Other actions – such as snow, traffic or ice – which will Other actions – such as snow, traffic or ice – which will modify the effects due to wind should be taken into modify the effects due to wind should be taken into account (see also EN 1993-1-3, EN 1991-2 and ISO FDIS account (see also EN 1993-1-3, EN 1991-2 and ISO FDIS 1249412494
The changes of structure during stages of execution – such The changes of structure during stages of execution – such as different stages of the form of the structure, dynamic as different stages of the form of the structure, dynamic characteristics etc - should be taken into account (see EN characteristics etc - should be taken into account (see EN 1991-1-6) 1991-1-6)
Where in design windows and doors are assumed to be shut Where in design windows and doors are assumed to be shut under storm conditions, the effect of these being open under storm conditions, the effect of these being open should be treated as an accidental design situationshould be treated as an accidental design situation
Fatigue due to effects of wind actions should be considered Fatigue due to effects of wind actions should be considered for susceptible structuresfor susceptible structures
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsWind velocity and velocity pressureWind velocity and velocity pressure
Basic valuesBasic values : : the fundamental values of the basic wind velocity the fundamental values of the basic wind velocity vvb,0b,0 is the characteristic 10 minutes mean wind velocity, is the characteristic 10 minutes mean wind velocity,
irrespective of wind direction and time of year, at 10m above irrespective of wind direction and time of year, at 10m above ground level in open country terrain with low vegetation such as ground level in open country terrain with low vegetation such as grass and isolated obstacles with separations of at least obstacle grass and isolated obstacles with separations of at least obstacle heights (category II).heights (category II).
The basic wind velocity shall be calculated with
vb = cdir cseason vb,o
wherevb is the basic wind velocity, 10m above ground, cat. IIvb,0 is the fundamental value of the basic wind velocitycdir is the directionsl factor (recommended 1,0)cseason is the season factor (recommended 1,0)
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsWind velocity and velocity pressureWind velocity and velocity pressure
Return period 50 yearsReturn period 50 years
0 10 20 30 40mittlere Windgeschwindigkeit in m/s
Rangfolgenstatistik
LSQ-Fit
Unterschreitenswahrscheinlichkeit
0.999
0.995
0.990
0.950
0.900
0.500
0.100
0.0010.010
0.9995
0.9999
"Jahresextremwerte"
0.98
vm,50=21.4m/s
= 1,5
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsWind velocity and velocity pressureWind velocity and velocity pressure
Mean wind Mean wind
– Variation with height Variation with height
v vmm(z) = c(z) = crr(z) (z) c c00(z) (z) v vb b
where where
cc00(z)(z) is the orography factoris the orography factor , , taken as 1, taken as 1,
» ccrr(z)(z) is the roughness factoris the roughness factor
ccrr(z)(z) = k= krr ln (z / z ln (z / z00) for z) for zminmin z z
zzmax max ccrr(z)(z) = c= crr(z(zminmin)) for z for z
zzmin min
07,0
,0
019,0
IIr z
zk
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsWind velocity and velocity pressureWind velocity and velocity pressure
Mean wind Mean wind
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsWind velocity and velocity pressureWind velocity and velocity pressure
Wind turbulence intensity IWind turbulence intensity Ivv(z) (z)
minzIzI vv
for z min z z max zv
kvk
zvzI
m
Ibr
m
vv
for z z min
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsWind velocity and velocity pressureWind velocity and velocity pressure
Peak velocity pressure qPeak velocity pressure qpp(z)(z)
bemvp qzczvzIzq 2
2
171
is recommended with 1,25 kg/m³
2
2
1bebep vzcqzcq
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsWind velocity and velocity pressureWind velocity and velocity pressure
Peak velocity pressure qPeak velocity pressure qpp(z)(z)
2
2
1bebep vzcqzcq
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsWind actionsWind actions
calculation procedures calculation procedures
– peak velocity pressure qpeak velocity pressure qpp
– wind pressures w, e.g. for cladding , fixings and structural partswind pressures w, e.g. for cladding , fixings and structural parts
– wind forces Fwind forces Fww on structures, e.g. for overall wind effects on structures, e.g. for overall wind effects
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsWind actionsWind actions
wind pressure on surfaceswind pressure on surfaces
we = qp(ze) cpe wi = qp(zi) cpi
ze,i is the (decisive) reference height for the external/internal pressure
cpe is the pressure coefficient for the external/internal pressure
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsWind actionsWind actions
Wind forcesWind forces
Fw,e = cs cd we Aref
Fw,i = wi Aref
Ff,e = cfr qp(ze) Aref
where.cs cd is the structural factorcfr is the friction coefficient Aref is the reference area of the structure or structural element
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsWind actionsWind actions
Wind forcesWind forces
Fw = cs cd cf qp(ze) Aref resp. Fw = cs cd cf qp(ze) Aref
where.cs cd is the structural factorcf is the force coefficient for the structure or structural elementAref is the reference area of the structure or structural element
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsStructural factor cStructural factor cs s ccdd
Determination of cDetermination of css c cdd
– For buildings with a height less than 15 m, the value of cFor buildings with a height less than 15 m, the value of css c cdd may be taken may be taken
as 1 as 1
– For facade and roof elements having a natural frequency greater than 5 Hz , For facade and roof elements having a natural frequency greater than 5 Hz , the value of cthe value of css c cdd may be taken as 1 may be taken as 1
– For framed buildings which have structural walls and which are less than For framed buildings which have structural walls and which are less than 100m high and whose height is less than 4 times the in-wind-depth, the 100m high and whose height is less than 4 times the in-wind-depth, the value of cvalue of css c cdd may be taken as 1 may be taken as 1
– For chimneys with circular cross-sections whose height is less than 60 m For chimneys with circular cross-sections whose height is less than 60 m and 6,5 times the diameter, the value of cand 6,5 times the diameter, the value of css c cdd may be taken as 1 may be taken as 1
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsStructural factor cStructural factor cs s ccdd
Determination of cDetermination of css c cdd
sv
svpds zI
RBzIkcc
71
21 22
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsPressure and force coefficientsPressure and force coefficients
GeneralGeneral Choice of aerodynamic coefficientChoice of aerodynamic coefficient
– Pressure coefficients for buildings and circular cylinders for Pressure coefficients for buildings and circular cylinders for internal and external pressuresinternal and external pressures
– Net pressure coefficients for canopy roofs, free-standing Net pressure coefficients for canopy roofs, free-standing walls, parapets and fenceswalls, parapets and fences
– Friction coefficientsFriction coefficients
– Force coefficients for signboards, structural elements with Force coefficients for signboards, structural elements with rectangular cross section, structural elements with sharp edged rectangular cross section, structural elements with sharp edged section, structural elements with regular polygonal section, section, structural elements with regular polygonal section, flags etc. flags etc.
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsPressure and force coefficientsPressure and force coefficients
GeneralGeneral Asymmetric and counteracting pressures and forcesAsymmetric and counteracting pressures and forces
Effects of ice and snow
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsPressure coefficients for buildingsPressure coefficients for buildings
Vertical walls of rectangular plan buildingsVertical walls of rectangular plan buildings
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsPressure coefficients for buildingsPressure coefficients for buildings
Vertical walls of rectangular plan buildingsVertical walls of rectangular plan buildings
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsPressure coefficients for buildingsPressure coefficients for buildings
Flat roofsFlat roofs
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsPressure coefficients for buildingsPressure coefficients for buildings
Monopitch roofsMonopitch roofs Duopitch roofs
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsPressure coefficients for buildingsPressure coefficients for buildings
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsPressure coefficients for buildingsPressure coefficients for buildings
Multispan roofsMultispan roofs
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsPressure coefficients for buildingsPressure coefficients for buildings
Vaulted roofs and domesVaulted roofs and domes
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsPressure coefficients for buildingsPressure coefficients for buildings
Internal pressureInternal pressure
•The internal pressure depends on the size and distribution of the openings•It should be taken into account if the openings are larger than 0,1% and not larger than 30% of the face area•In certain cases the internal pressure may be handled as an accidental load
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsPressure coefficients for buildingsPressure coefficients for buildings
Pressure on walls or roofs with more than one skinPressure on walls or roofs with more than one skin
– The wind force is to be calculated separately on each skinThe wind force is to be calculated separately on each skin
– The permeability The permeability of a skin is defined as the ratio of the total of a skin is defined as the ratio of the total area of the opening to the total area of the skin. A skin is area of the opening to the total area of the skin. A skin is defined as impermeable if defined as impermeable if is less than 0,1 % is less than 0,1 %
– If only one skin is permeable, then the wind force on the If only one skin is permeable, then the wind force on the impermeable skin should be determined from the difference impermeable skin should be determined from the difference between the internal and the external wind pressurebetween the internal and the external wind pressure
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsForceForce coefficients for canopy roofs coefficients for canopy roofs
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsForceForce coefficients for canopy roofs coefficients for canopy roofs
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsFree Free standing walls, parapets, fences and signboardsstanding walls, parapets, fences and signboards
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsFriction coefficientsFriction coefficients
l = 2b or 4h
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsStructural elementsStructural elements
Structural elements with rectangular sectionsStructural elements with rectangular sections
Structural elements with sharp edged sectionsStructural elements with sharp edged sections
Structural elements with regular polygonal sectionStructural elements with regular polygonal section
cf = cf,0 · r · A
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsCircular cylindersCircular cylinders
External pressure coefficientsExternal pressure coefficients
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsCircular cylindersCircular cylinders
Force coefficientsForce coefficients
Force coefficients for vertical cylinders in a row arrangementForce coefficients for vertical cylinders in a row arrangement
cf = cf,0 ·
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsSpheresSpheres
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsLattice structures and scaffoldingsLattice structures and scaffoldings
cf = cf,0 ·
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsFlagsFlags
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsEffective slenderness Effective slenderness and end-effect and end-effect
= A/Ac
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsAnnex A (informative) – Terrain effectsAnnex A (informative) – Terrain effects
Illustrations of the upper roughness of each terrain categoryIllustrations of the upper roughness of each terrain category
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsAnnex A (informative) – Terrain effectsAnnex A (informative) – Terrain effects
Illustrations of the upper roughness of each terrain categoryIllustrations of the upper roughness of each terrain category
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsAnnex A (informative) – Terrain effectsAnnex A (informative) – Terrain effects
Numerical calculation of orography coefficientsNumerical calculation of orography coefficients
vm: mean wind velocity at height z above terrainvmf: mean wind velocity above flat terrainco = vm/vmf
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsAnnex A (informative) – Terrain effectsAnnex A (informative) – Terrain effects
Numerical calculation of orography coefficientsNumerical calculation of orography coefficients
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsAnnex A (informative) – Terrain effectsAnnex A (informative) – Terrain effects
Neighbouring structures – Displacement heightNeighbouring structures – Displacement height
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsProcedures for determining the structural factor cProcedures for determining the structural factor cssccdd
Spectrum of the responseSpectrum of the response
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsProcedures for determining the structural factor cProcedures for determining the structural factor cssccdd
Detailed procedureDetailed procedure
sv
svpds zI
RBzIkcc
71
21 22
sv
svs zI
BzIc
71
71 2
2
22
71
21
BzI
RBzIkc
sv
svpd
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsProcedures for determining the structural factor cProcedures for determining the structural factor cssccdd
Background factor B²Background factor B²
conservative: B² = 1conservative: B² = 1
63,02
9,01
1
szLhb
B
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsProcedures for determining the structural factor cProcedures for determining the structural factor cssccdd
Resonance response factor R²Resonance response factor R²
Peak factor kPeak factor kpp
bhL RRSR
2
22
22
2
,1 RB
Rn x
sec600T
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsProcedures for determining the structural factor cProcedures for determining the structural factor cssccdd
Number of loads for dynamic responseNumber of loads for dynamic response
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsProcedures for determining the structural factor cProcedures for determining the structural factor cssccdd
ccssccdd values for different types of structures values for different types of structures
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsVortex shedding and aeroelastic instabilitiesVortex shedding and aeroelastic instabilities
Kraftwerk Ferrybridge, GB, am 5. Nov. 1965: Einsturz von 3 Schalenkühltürmen aus Stahlbeton
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsVortex shedding and aeroelastic instabilitiesVortex shedding and aeroelastic instabilities
Criteria for vortex sheddingCriteria for vortex shedding
vcrit,i 1,25 vm
wherevcrit,i is the critical wind velocity for mode i
vm is the characteristic 10 minutes mean wind velocity at the cross section where vortex shedding occurs
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsVortex shedding and aeroelastic instabilitiesVortex shedding and aeroelastic instabilities
Vortex shedding actionVortex shedding action
Fw(s) = m(s)·(2··ni,y)² · i,y(s) · yF,max
wherem(s) is the vibrating mass of the structure per unit length
ni,y is the natural frequency
I,y(s) is the mode shape of the structure normalised to 1 at the point with the max. displacement
yF,max is the maximum displacement over time of the point with I,y(s) equal to 1
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsVortex shedding and aeroelastic instabilitiesVortex shedding and aeroelastic instabilities
GallopingGalloping
Interaction effectsInteraction effects
vCG 1,25 vm
with
vCG = 2 · Sc · n1,y · b / aG
5,17,0 crit
CG
V
V
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsDynamic characteristics of structuresDynamic characteristics of structures
GeneralGeneral
– natural frequenciesnatural frequencies
– modal shapesmodal shapes
– equivalent massesequivalent masses
– logarithmic decrements of dampinglogarithmic decrements of damping
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsDynamic characteristics of structuresDynamic characteristics of structures
Fundamental frequencyFundamental frequency
11 2
1
x
gn
][46
1 Hzh
n for multi-storey buildings with a height larger than 50m
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsDynamic characteristics of structuresDynamic characteristics of structures
Logarithmic decrement of dumpingLogarithmic decrement of dumping
= s + a + d
e
smfa mn
zvbc
12
)(
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsWWind mapind map
Historische Orkane :
1976 Capella1984 Münchener Hagelsturm1990 Winterstürme Daria (Jan), Vivian (Febr), Wiebke (Febr), Gesamtschaden in Preisen von 1990: 25 Mrd. DM 1999 Lothar
Modell für einen Europa Orkan zur Prognose des Sturmrisikos in Deutschland und den Benelux-Staaten (Münchner Rück)
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsWWind mapind map
EUROCODE 1 – Part 1-4: Wind EUROCODE 1 – Part 1-4: Wind actionsactionsWWind mapind map