Can any one explain about gust factor?

What is the definition of the gust factor?
When we apply it in the column calculation?

What is the effect of the gust factor in the column calculation?

Explanation and definition of Gust Factor is available in IS-875. Formula for calculation is also available.

Dear Pradeep,

Gust factor is the ratio of the “maximum gust speed” within a specified period to the “mean wind speed”. Basically the gust means the sudden impact of wind on the structure, which can cause vibration i.e. dynamic deflection of the structure, will increases.

This factor has higher significance where slenderness ratio is high. As per PVElite if L/D ratio is greater than 5, then effect of gust factor should have to take into account.

For the case of the columns, they have high L/D ratio, which can cause maximum deflection of the whole structure. With respect to their height they should be able to sustain the effect of the gust.
As it is the factor, it increases the element wind load (IS 875). Also “maximum gust velocity” is the function of the gust factor & if it is less than the critical wind velocity then structure becomes free from vibration.
Maximum gust velocity is the relation between “maximum wind velocity” & “Gust factor”. As high as the height of the vessel, “maximum wind velocity” will also be high.



Thanks,
Makrand.