SCALE + FORM
Normalised spectral energy of across-wind modal force
5.6 Wind tunnel testing 5.7 Reduction of wind forces 5.8 Wind tunnel test result: model frequency related to the recurrence interval for wind events. The vertical axis is proportional to the resonant dynamic forces divided by the square of the wind velocity. a Original building configu ration b Configuration after several refinements of the architectural massing 5.9 Burj Khalifa 5.10 Tianjin CTF Financial Centre, Tianjin (CN), anticipated completion 2018 5.11 Wind tunnel workshop, Tianjin CTF Financial Centre, BMT Wind Tunnel 5.12 Wind tunnel tested schemes, Tianjin CTF Financial Centre
Initial scheme Base moment Acceleration 5.6
wind tunnel testing was undertaken, during which the structural and architectural teams refined the tower’s shape to increase its performance. Wind tunnel testing was performed in Rowan Williams Davies and Irwin Inc.’s (RWDI) boundary layer wind tunnels in Guelph, Ontario. The wind tunnel programme included rigidmodel force balance tests, full multi-degree of freedom aeroelastic model studies, measurements of localised pressures, pedestrian wind environment studies and wind climatic studies (Fig. 5.6). Using the wind tunnel to understand and optimise wind performance was crucial to the tower’s design. Several rounds of force balance tests were undertaken as the tower’s geometry evolved and became refined.
1.6
Nose A Tail A Nose B Tail B Nose C Tail C
1.4 1.2 1.0
Intermediate scheme
Final scheme
65 % 0
100 %
0
100 %
76 % 0
60 % 0
100 %
0
100 %
Tallest tested scheme
100 %
72 % 0
66 % 0
100 %
100 % 45 %
0
100 % 5.7
After each round of wind tunnel testing, the data were analysed, the building was reshaped to minimise wind effects and the building’s harmonics were refined (Fig. 5.7). In general, the number and spacing of the setbacks changed, as did the shape of the wings – originally, the setbacks were arranged in a spiralling counter-clockwise manner, which was reversed during testing to clockwise. Wind directionality was also studied, with respect to considering the direction of the frequent and strongest winds. As a result, the tower orientation was changed so as to better accommodate the most frequent strong wind directions for Dubai: northwest, south and east. Through wind-tunnel testing, the tower’s struc-
1000 yr 4.21 Hz 100 yr 4.90 Hz 10 yr 5.69 Hz 1 yr 6.8 Hz
0.8 0.6 0.4 0.2 0 1.00
Normalised spectral energy of across-wind modal force
a
2.00
3.00
4.00
5.00
6.00
7.00
8.00
1.6
9.00 10.00 Frequency [Hz] 1000 yr 4.04 Hz 100 yr 4.69 Hz 10 yr 5.58 Hz 1 yr 6.80 Hz
1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 1.00
b
2.00
3.00
4.00
5.00
6.00
7.00
8.00
9.00 10.00 Frequency [Hz] 5.8
60
5.9