Item File 20485 Eurocode 1-4-A-wind

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

QQ

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)


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


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


Mean wind Mean wind


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


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


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


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


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


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


Flat roofsFlat roofs


Monopitch roofsMonopitch roofs Duopitch roofs


Multispan roofsMultispan roofs


Vaulted roofs and domesVaulted roofs and domes


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


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 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


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


Numerical calculation of orography coefficientsNumerical calculation of orography coefficients


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


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


Background factor B²Background factor B²

conservative: B² = 1conservative: B² = 1

63,02

9,01

1

szLhb

B


Resonance response factor R²Resonance response factor R²

Peak factor kPeak factor kpp

bhL RRSR

2

22

22

2

,1 RB

Rn x

sec600T


Number of loads for dynamic responseNumber of loads for dynamic response


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


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


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


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


Fundamental frequencyFundamental frequency

11 2

1

x

gn

][46

1 Hzh

n for multi-storey buildings with a height larger than 50m


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

Item File 20485 Eurocode 1-4-A-wind

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Transcript of Item File 20485 Eurocode 1-4-A-wind