CHANNEL 9 NEWS FEATURE
Fierce winds take Australia by storm
Tall buildings are appearing in and around Australian cities at an exponential rate, with rapid population growth and economic development likely the key catalysts. This, combined with an increase in windy weather, is potentially a lethal combination.
To gain a greater insight into this phenomenon, the Channel 9 film crew recently visited Vipac’s laboratories and interviewed Chairman Wendy Smith and their Wind Engineering expert about why the lateral wind load imposed on tall buildings is one of the governing factors in their structural design.
The benefits of tall buildings are palpable. They provide a high ratio of rentable floor space per unit area of land, their centralised HVAC systems enable efficient heating and cooling, and they can be covered by renewable energy or another electricity generation of lower greenhouse gas emissions.
But high-rise buildings are among the more wind-sensitive structures, with many wind-induced comfort and serviceability concerns. For example, the design of high-rise buildings must take into account the comfort criteria due to the wind-induced vibration. While wind that approaches and flows within buildings is widely considered a complex phenomenon, it is the wind flow pattern generated around tall buildings that make predictions all the more complicated.
According to global satellite data analysis, wind speeds have increased 5 per cent on average over the past 20 years, with strong winds caused by storms jumping as much as 10 per cent. The Bureau of Meteorology issued no less than 50 severe weather warnings in Melbourne alone for the month of October, 2016.
As buildings get taller, thinner, lighter and more complex in shape, wind loads even in equatorial zones become significant. To ensure these dynamic loads are well defined and understood, boundary layer wind tunnel testing is used for:
- Total load determination, excitation at lower order structural and torsional modes
- Façade or cladding load levels which will impact directly on curtain wall and glass selections
- Ground level winds around the building and the interaction with automatic entry doors – aspects which often affect the comfort and use of spaces around the base of the building.
Wind tunnel studies can also be used to optimise HVAC systems, cooling tower performance and the building’s ability to capture and direct down-wash winds to flush away pollutants and provide comfortable outdoor spaces.
At Vipac, we provide design evaluations of cities and groups of buildings, including wide area studies, through medium sized public open space to specific buildings, evaluating engineering dynamics aspects including forces, pressures, dynamic response and thermal comfort.
Who we help:
Town Planners: Facilitate building approval by providing reports recommending wind control measures to accompany vital documents submitted to authorities
Building Owners: Test designs prior to construction using to scale models and attaching up to 3,000 sensors to accurately measure the wind flow once it’s placed in a wind tunnel. These results help determine the cladding specifications for the final design.
Architects: Using internationally accepted pedestrian wind criteria and local wind climate information, Vipac’s consultants can facilitate building design conducive to wind, identify wind sensitive locations and create wind mitigation measures such as wind break devices to ensure public safety and comfort.