Tall columns deflection

Tall columns sway in the wind. The allowable deflection will normally be specified as less than 150 mm per 30 metres of height (6 in. per 100 ft). 

The sway of the tower will produce a maximum velocity as the tower passes through vertical center. Also, the maximum velocity of sway will be at the top of the column with zero velocity at the base. As the column reaches the limit of its deflection, the kinetic energy of motion is transferred to strain enei of the shell, causing reversal of direction. The column will sway back and forth until the energy is dissipated. The total strain energy stored in a tall vertical tower at its point of maximum deflection during sway is given by the equation... 

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