Wind Farms Usually Involve Several Wind Turbines

On the other hand, the effect of wind on large structures is something that structural engineers need to analyze in order to ensure the safety of these structures. Some examples of structures that are heavily affected by wind are skyscrapers, towers, cable suspension bridges, and the wind turbines mentioned above. Here, wind is like a curse because structures can fail and collapse under heavy winds if precautions against wind effects are not taken when designing these structures.

For a wind turbine, winds cause a bending moment in the shaft of the turbine. This is because vertical wind speed profiles are not uniform (more so on land than over water), meaning the wind speeds at low elevations and high elevations are different. This difference in wind speed causes a difference in forces at the top and bottom of the wind turbine shaft, which makes the shaft want to bend. Too much bending moment will cause a wind turbine to break and collapse. Engineers have a variety of tools at hand to help them combat this challenge of wind loads, such as building material to use (different materials have different properties against failure), and geometry of the shaft (like the cross-sectional shape and area of the shaft).

For cable bridges, high winds can cause vibrations in the bridge. One famous historical example of a suspension bridge is the Tacoma Narrows Bridge (Wikipedia). Opened in 1940 to traffic in Washington state, it collapsed four months later due to high winds that caused large periodic motions of the bridge. Forces on the bridge from the wind combined with the natural frequency of the bridge to result in large-scale fluttering, which is a phenomenon known as aeroelastic flutter. You can see video footage of the Tacoma Narrows Bridge collapse here (YouTube).

The Tacoma Narrows Bridge collapse serves as a lesson learned in today’s world of engineering. Ways that engineers can safeguard against suspension bridge failure due to high winds include considering stiffness of the bridge and how the bridge deck is constructed, as well as studying the winds themselves (looking at historical wind speed data for a particular area).

Next time you walk outside and experience a heavy wind in your face, know that winds are a necessary evil. Sure, they are something that engineers need to consider when designing large buildings and bridges, but they also serve as a renewable source of energy.

Photo from Wikipedia.