We often take the raw power of wind for granted, considering it a mere nuisance blowing leaves and litter around like some weakling—except, of course, when there is a severe storm that we have to deal with.
However, with tower cranes, the case is entirely different, where even the seemingly humble air currents can cause significant disaster due to “amplified” wind loads.
Effects of Wind on Tower Cranes
Air is a mixture of various gases, where each gas in the mixture has a certain density. When the wind blows, the molecules of the gases in the air gain energy and are moved at different velocities depending on their size and mass. When these molecules encounter a surface in their path, they give some of their energy to the surface and consequently exert pressure onto it. This pressure is defined as:
VP = KVS2, where
VP is the wind pressure
K is the density of a gas, which for design purposes is considered constant at 0.613
VS is the wind speed
As can be seen from the above equation, there exists a squared relationship between win pressure and wind speed. So if you double the wind speed, the wind pressure increases by a factor of four times.
This is a crucial point to note because it underscores how a small increase in wind speed can significantly increase its impact.
Wind speed itself is a function of height, i.e., wind speed increases with height. So the higher you go above the ground, the harder the wind tends to blow.
Since tower cranes are erected at great heights, and sometimes even on top of buildings, the wind can easily reach speed levels where its raw power can become unforgiving and brutal for crane operations. It can destabilize a tower crane or the load on the hook and create potential accident situations. With the center of impact also at a significant distance from the ground, the overturning moment can get further amplified, making the operations even more difficult and dangerous for crane operators.
That’s why it’s recommended that tower cranes should always be operated below maximum permissible speed and crane operators should continuously monitor crane wind speed when performing a lift.
Here, at Crane Warning Systems Atlanta, we sell a variety of crane safety instrumentation systems, including crane Wind Speed Indicator system. Visit our online store to learn more about our crane-exclusive wind speed indicators.