Helping the tallest building in Hong Kong efficiently withstand typhoons
The International Commerce Centre (ICC) is a 118-storey, 484m skyscraper in Hong Kong’s West Kowloon Cultural District. Situated atop Kowloon Station, the ICC is the tallest building in Hong Kong.
Wind is a major engineering consideration – and a major driver of construction costs – in high-rise buildings, especially in typhoon-prone areas like Hong Kong.
The ICC’s designers knew that the tower’s location on the South China Sea would subject it to extremely strong wind forces. They needed to develop a design that would have adequate strength for the demands imposed by the wind pressures, limit wind-induced vibration to ensure occupant comfort, while also ensuring that the tower’s design not be prohibitively expensive to construct. They approached our team for detailed intelligence about the wind effects the ICC would face and guidance on efficient aerodynamic mitigation strategies.
It was clear from the outset that the project called for boundary layer wind tunnel testing, which provides engineers with accurate information about their buildings’ performance in high winds. This information enables design teams to achieve the right balance between the structures’ safety and comfort on one hand, and the economical use of materials on the other.
To ensure the reliability of the design information derived from the wind tunnel testing, we needed to ensure that we accurately modeled two key aspects of the ICC’s environment: typhoons and topography.
Typhoons dominate Hong Kong’s wind climate. These extreme wind events are variable by nature: their timing, direction, and intensity can all vary substantially. To help the ICC’s designers develop an optimal design for the structure and building envelope, we needed to help them account for the full range of extreme windstorms the ICC would need to withstand, so we developed a statistical model of Hong Kong wind conditions. We gathered historical wind speed records from a local weather station, and in combination with a “Monte Carlo” simulation of future storms generated by Applied Research Associates, created a statistical model of the wind climate. Monte Carlo simulations are probability-based mathematical models that forecast future events. In this case, the Monte Carlo model was based on many randomly generated samples of possible future typhoons in the Pacific Ocean – with myriad combinations of wind intensity and directionality. In effect, using the output from this model allowed us to account for the impact of 100,000 years of tropical storms to ensure the ICC would be capable of withstanding whatever conditions it might face.
Hong Kong’s unique topography was another important factor to consider. The dramatic landscape of mountains and valleys that surround the dense harbor city can produce varying effects on wind velocity and turbulence intensity, depending on the direction the wind is coming from. So in order to ensure the validity of our wind tunnel testing process, we had to capture the effects of Hong Kong’s topography on the proposed tower. To provide truly accurate modeling of the wind characteristics at the ICC project site, we constructed a 1:3000 scale model, including all major topographical features within a 7.3 km radius of the center of the project site. The tests were specifically used to identify the effects of the surrounding topography on the speed and turbulence intensity of the winds as they approached the building from different directions.
Together, the rich intelligence we were able to deliver on both the characteristics of typhoons and the effects of the surrounding topography helped the ICC’s designers maximize structural efficiency and minimize construction costs while ensuring that the tower would perform well in the windstorms it was expected to face.
The ICC has been operating successfully since its completion in 2010. It has earned a number of awards, including a 2015 International Building Performance Award, a 2014 Council on Tall Buildings and Urban Habitat Performance Award, a Merit Award for Architecture from the American Institute of Architects in Hong Kong (2010), and a Gold award in 2011 from MIPIM Asia, a real estate association.
In 2012, the tower performed well as Typhoon Vicente made landfall, recording 10-minute mean wind speeds of 140 km/h and provoking the Hong Kong Observatory to issue a Hurricane Signal, No. 10, the first one it had issued since 1999.