3. Wind load is the load placed by the wind speed and it is
air density onto a building, with high velocity winds, low
pressure areas are created on the building which creates
section pressure. Some are so strong that they can pull of
the corner of a roof.
The effect of wind on the structure as a whole is
determined by combined action of external and internal
pressures acting upon it .
We can use wind load analysis the structure having more
then 10 to 30 meters.
It is design as per IS code :875(part 3) -1987
5. Wind flow pressures that create a strong lifting effect, much
like the effect on airplane wings . Wind flow under a roof
pushes upward ; wind flow over a roof pulls upward.
6. Horizontal wind pressure that could cause racking of walls
making a house tilt .
7. Horizontal pushing and pulling pressure on walls that
could make a house slide off the foundation or overturn.
8. “Wind effects on structures can be classified as static and
dynamic .
Static :-
Static wind effect primarily causes elastic bending and
twisting of structure.
Dynamic :-
For tall , long span and slender structures a Dynamic
analysis of the structure is essential wind gusts cause
fluctuating forces on the structure which induces large
dynamic motions , including oscillations .”
9. In the majority of structures , it is satisfactory to treat wind
as a static load . The factors which determine the proper
equivalent static pressure(p e) are best understood through
the following equation presented by Davenport (1960 ):
Pe = C S .C a .C g . q
10. C a = a coefficient depending upon nearby
topographic features
C g = a gust coefficient dependent upon the
magnitude of gust velocities and size of the structure
q = dynamic-pressure intensity ,given by
q =1/2 𝜌 𝜐h
2
12. Design wind speed as per IS 875-1987
The design wind speed is obtained by multiplying the basic
wind speed(Vb) by the factor k1, k2, k3:
Vz = Vb k1 k2 k3
K1= probability factor
K2=terrain height and structure size factor
K3=topography factor
