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Wacker Ingenieure | Wind EngineeringGewerbestrae 2 | 75217 Birkenfeld |Germany | www.wacker-ingenieure.de
Wind Impact on Textile Structures
J. Wacker
TensiNet Symposium, Newcastle, UK, 26th 28th of October 2016

About Wacker Ingenieure, Wind Engineering
2
Own model fabrication shop
Office in Birkenfeld, Germany 3 own wind tunnels
Codes for numerical flow simulations

Typical structures to be investigated with regard todifferent Wind Engineering Aspects
3
Special constructions
Not covered directlywithin standards
=

Textile Structures = Special Structures
4
Al Bayt Stadium, Al Khor City, Qatar
New Stadium in Caracas, Venezuela

Textile Structures: Wind Engineering Aspects
5
Structural and localwind loads
Wind-inducedvibrations
Natural Ventilation
Wind comfortinside / outside
Smoke extraction in case of fire
Wind-inducednoise
Wind-inducedrain infiltration
Snow loads, driftand accumulation
Structural engineer Fire engineer Architect
Sand loads, driftand accumulation

Textile Structures: Wind Engineering Aspects
6
Structural and localwind loads
Wind-inducedvibrations
Today:

Wind Impact on Typical Textile Structures
7
Examples for shapes not covered in codes
Wind tunnel modelling most appropriatemethod to acquire wind pressure data.
For structural design of textile structures:
realistic wind loads are required including dynamic wind loads

Wacker Ingenieure | Wind EngineeringGewerbestrae 2 | 75217 Birkenfeld |Germany | www.wacker-ingenieure.de 8
Due to
Great variability and complexity of shapes
Geometrically complex eigenmodes, often across-wind vibrations
Membrane structures often attached to bigger structures that complicatethe wind situation and enhance turbulence and dynamic excitation
Wind tunnel testing of textile structures necessary,realistic evaluation of dynamic responses is complicated
no proper code approaches available, wind loads extremely case-dependent!
Wind Tunnel Testing of Textile Structures

PCA D
Filter +
Verstrker
SurroundingsFence
Differential pressure
transducers
Approach flow
Spires
Reference pressure (static pressure of the flow)
Simultaneous measurement
of pressure time series
Pressure taps
Measurement of the reference wind speed
Floor roughness
Fans
Honeycombs
Pitot static tube
Turn table
Test building
Filtering +Amplification
Differential pressure transducer
Voltmeter
Wind tunnel testing - Equipment
Schematic section of boundary layer wind tunnel
Rigid or aeroelasticbuilding model;scale 1:100 to 1:500)
Simulation ofatmosphericboundary layer
Wind pressure time series cp(t)

Formerly:
W = cp,mean * qgust [kN/m2]
Then:
W = (cp,mean +/- k * cp,rms) * qmean [kN/m2]
Today:
Measurement of cp(t) simultaneously within the area of interest Extraction of critical load pattern with regard to different
responses of interest Weighting with influence functions (customized load cases) Calculation of dynamic responses in time domain (several modes) Consideration of added mass and aerodynamic damping effects
Wind Loads on Textile Structures:Development of Methodology
Wind pressure time series cp(t)
Typical influence function
cp = p/ q

Case study 1: Large textile umbrellas
Projects in Medina and Mecca, Saudi Arabia Umbrellas up to 53 m x 53 m
Full-scale tests

Wind tunnel simulation
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Wind pressure distributions on umbrellas
1) maximum bending moment at base2) maximum overall suction (upward wind force)3) maximum overall pressure (downward wind force)
(1) (2) (3)
Simultaneous measurements of wind pressure time series cp(t) on upside anddownside of umbrella membranes allow evaluation of time-varying pressure field;
Time-varying pressure field reveals typical load patterns which are extractedin order to cover typical peak events (load cases)
Blue = upwardRed = downward[cp,net]

Total vertical wind forces on umbrellas
Integration of pressure field results in total (global) forces acting on umbrellas;
The time-series of vertical force Fz shown below exhibits strong upwards anddownwards peaks despite low mean forces, there are pronounced eventsproducing high overall suction and high overall pressure;
pressure events
suction events
time
overalluplift

Wind-induced dynamic response of umbrellas
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time-varying cp,net-distribution on umbrella and dynamic response (see bottom plotfor effective base moment).
Effectivebase moment
time

Conclusion Case Study 1: Large textile umbrellas
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Simultaneous akquisition of time-dependent wind pressure field isimportant to be able to consider different load patterns which result in different load cases for one and the same wind direction
Consideration of of dynamic wind effects is necessary; consideration in time domain and consideration of several modes yields higher accuracy, corresponding inertia forces cause higher effective loads

Case Study 2: Huge flat textile roof structure
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Horizontal flat fabric roof
- Operable (retractable)- Size about 180 x 90 m- exposed to strongly turbulent
wind (built-up surrounding)

Wind tunnel tests: Surface pressure distribution
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Quasi-static time-varying cp,net-distribution obtained from wind-pressure time series (wind tunnel tests) showing both pronounced pressure and suction events:
[cp,net]
overalluplift
time

Dynamic Response: Implementation of 12DOF-model
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Membrane oscillation caused by short-time vertical force pulse in its center shows need of considering more than 1 eigenmode; (animation below based on 12 modes; multimodal representation)
fe,3=0.49 Hz
fe,2=0.42 Hz
fe,3=0.47 Hz
fe,1=0.32 Hz
Eigenmodes

Dynamic Response: Consideration of added massand aerodynamic damping
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very light roof with1st eigemode like horizontal beam
Movement of membrane up anddown caused by wind
Air masses above and beneath moving membrane will be moved, too, andconsequently, damping and eigenfrequencies will be changed.
2D-FSI-simulation of middle section was performed for oscillating roof after initial displacement in order to check effective damping and added mass effects.
Afterwards the original structural parameters, i.e. structural damping and eigenfrequencies, were adapted carefully.

Dynamic response caused by wind
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Wind-induced oscillations (top) and quasistatic and effective vertical force Fz (bottom)
effectiveverticalforce Fz
time
blue = qstatgreen = effective

Final effective load distributions
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cp,net-distribution for load casepressure without dynamic effects(quasi-static wind load):
cp,net-distribution for load case pressureincluding inertial contributions from themoving membrane mass):
Elaboration of representative load cases for respective target variables
Without dynamics With dynamics
[cp,net]

Wacker Ingenieure | Wind E

wind impact on textile structures - newcastle · pdf filewind impact on textile structures j....

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