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Construction : Web Exclusive | August 2016 | Source : CW-India

How wind tunnel testing can be best done for high-rises!

Wind pressure plays a major role in designing tall and super tall buildings. Structural wind load study allows designers to examine complex load effects in detail by providing loading results in a format that is ready-to-use in most structural design applications. A wind-induced motion and structural load review may be used to provide preliminary estimates of the overall structural wind loads, and building motion for human comfort and cost analysis. “It not only reduces the cost but optimises in establishing the design criteria, thus having minimum impact on the environment as well,” shares Nayan Raheja, Executive Director, Raheja Developers.
Wind loading parameters recommended by Indian Standard Codes serve as simple guidelines, which can be safely adopted for buildings of moderate height and broad base. “However, for buildings beyond 120 m height and having an aspect ratio of more than five, it is necessary to get a wind tunnel testing done. If such a specialised agency is appointed right from the concept design stage, valuable suggestions received from them can save overall cost of construction,” shares Kamal N Hadker, Managing Director, Sterling Engineering Consultancy Services
Before the construction of tall buildings, at the preliminary design stage, wind pressures on glass facades, wind loads on structural frames and building motions can be determined with local codes or standards. “But this provides only a first cut number for preliminary design; later, the scaled model of the building should be tested in a wind tunnel to determine the various wind-induced responses accurately,” says senior wind engineering consultant K Suresh Kumar, Principal and Managing Director, RWDI Consulting Engineers (India). Wind tunnels are long boxes with a fan at one end and instrumented model at the other; when the wind blows, the building’s response parameters are measured and analysed to come with recommended design loads. The wind tunnel-derived loads supersede code-derived loads and are used for the final design. “Once constructed, the pressures and motion of the building can be monitored using equipment. But at this stage, these measured quantities are only useful to compare with wind tunnel-derived numbers and for the betterment of wind tunnel simulation,” adds Kumar.
Wind tunnel test allows you to design a building for optimum and for its type, simulating extreme conditions. “In Omkar 1973, in case of a particular wind velocity, there will be an alarm, asking for windows to be closed,” shares Raman Sapru, President-EPC, Omkar Realtors & Developers.
Indeed, wind tunnel test is a prerequisite for any high-rise.
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