1. Large roofs and sports stadiums
Wind loading and structural response
Lecture 20 Dr. J.D. Holmes
Large roofs and sports stadiums

2. Large roofs and sports stadiums
Entertainment centres, exhibition centres, sports arenas etc
Quasi-steady approach is not applicable
Resonant effects can be significant
Bending moments in arches and domes are sensitive to distribution of wind load

3. Large roofs and sports stadiums
General flow characteristics :
Separation “bubble”
Stagnation Point
Fluctuating re-attachment point
Shear layer positions:
High turbulence
Low turbulence
Mainly attached flow on large roofs

4. Large roofs and sports stadiums
General flow characteristics :
Separation point
On arched roof, separation occurs downstream of apex

5. Large roofs and sports stadiums
Mean pressure distributions :
U.W.O.
Wind-tunnel tests
Fluctuations in pressure will generate downwards pressures for short times

6. Large roofs and sports stadiums
Mean net pressure distributions (cantilevered stadium roof):
blocked at rear
-1.3
-1.2
-1.1
-1.0
-0.7
-0.6
-0.4
-0.2
-0.1
-0.8
0.0
0.2
0.1
-1.4
C/L
gap at rear reduces net pressures

7. Large roofs and sports stadiums
Arched roof : L S R he
wind loads depend strongly on R/S (rise/span)
less strongly on L/S and he/S

8. Large roofs and sports stadiums
Arched roof (Cp) :
+0.4
-0.4
-0.8
+0.3
+0.2
-0.3
-0.6
+0.5
-0.5
-0.25
R/S = he/R = L/S =  = 0o
increasing L/S  pressures on roof become more negative

9. Large roofs and sports stadiums
Arched roof (Cp) :
-0.3
-0.7
+0.2
-1.0
-0.4
-0.5
+0.4
+0.3
-0.2
-0.6
+0.1
-0.45
-0.9
higher negative values

10. Large roofs and sports stadiums
Arched roof (Cp) :
-0.2
-0.25
-0.3
-0.4
-0.5
-0.7
-0.9
+0.4
+0.2
+0.5
-0.15
positive
lower negative values
R/S = he/R = L/S =  = 0o

11. Large roofs and sports stadiums
Structural loads - effective static load distributions
Instantaneous pressure distributions vary greatly from time to time due to turbulence, vortex generation etc. Shapes may vary greatly from the mean pressure distribution
Need to identify those distributions which produce maximum load effects

12. Large roofs and sports stadiums
Structural loads - effective static load distributions
Wind-tunnel methods for design wind loads :
1) Direct approach : simultaneous time histories from the whole roof are recorded and stored. Later weighted with structural influence coefficients to obtain time histories of load effects. Instantaneous pressure distributions are identified and averaged.
2) Correlations between pressure fluctuations at different parts of the roof are measured and used to determine effective static load distributions (Lecture 13, Chapter 5)
Correlations for separated parts of a large roof are low: hence potential for significant reduction in peak effective loads and peak load effects (b.m.’s, axial forces etc.)

13. Large roofs and sports stadiums
Structural loads - effective static load distributions
Arch roof (Kasperski,1992) :

14. Large roofs and sports stadiums
Structural loads - effective static load distributions
Sydney Olympics, 2000
Superdome
Stadium Australia

15. Large roofs and sports stadiums
Structural loads - effective static load distributions
Sydney Olympics, /500 wind-tunnel model
Stadium Australia
Superdome

16. Large roofs and sports stadiums
Structural loads - effective static load distributions
Stadium Australia (Sydney Olympics, 2000)
Panel layout for wind-tunnel testing

17. Large roofs and sports stadiums
Structural loads - effective static load distributions
Stadium Australia (Sydney Olympics, 2000)

18. Large roofs and sports stadiums
Structural loads - effective static load distributions
Stadium Australia (Sydney Olympics, 2000)

19. Large roofs and sports stadiums
Structural loads - effective static load distributions
Superdome (Sydney Olympics, 2000)

20. Large roofs and sports stadiums
Structural loads - effective static load distributions
Superdome (Sydney Olympics, 2000)
Effective static load distributions for axial loads in a particular roof member

21. Large roofs and sports stadiums
Structural loads - contribution from resonant modes
Usually not significant for roofs supported all round or on two sides
May be significant for cantilevered roofs :
Time
Vertical upwards
Very large roofs may have several modes below 1 Hertz
- contributions to load effects depend on similarity of mode shapes with influence lines

22. End of Lecture 20 John Holmes 225-405-3789 JHolmes@lsu.edu