WIND INTRODUCTION
For K2 Refer Table 2 of IS:875-3
Category 1 No obstructions available to the building ex : Sea
coasts and flat tree less Plains where other structure if
:
any have heights less than 1.5 m
Category 2 : Open terrain with well scattered obstructions of 1.5 m to 10 m height
Category 3 : Refer to area of closely spaced buildings of heights upto 10 m
Category 4 : Refer to area with highly closed buildings of large heights
Factor K2 also depends on the dimensions of the building under consideration.
The structures are classified as
Class A : max l,b,h : <20 m
Class B : max l,b,h : 20 to 50 m
Class C : max l,b,h : > 50 m
For K3 Wind motion depends on topography of the area
if upward wind slope Theta <=3 : K3=1 Refer code
Theta > 3 : K3=1.0 to 1.36
Step 1 : Design Wind Speed (Vz) :
Vz = Vb X K1 X K2 X K3
Where Vb = Basic Wind Speed
K1 = Risk Coefficient
K2 = Terrain height and structure size factor
K3 = Topography Factor
Step 2 : Design Wind Pressure pz' (6.2.1)
The Design wind pressure at any height above mean Ground level shall be obtained by the
pz = 0.6 Vz2
Where pz = Design wind Pressure in N/m2 at height Z
Vz = Design wind speed in m/sec
Wind Loads on Buildings :
Wind Load : Net pressure acting on the surface and the surface area.
Net Pressure : Algebraic sum of external and internal wind pressure acting on the surface.
external pressure coefficient,depends on the dimensions,roof angels and
Cpe : shape of the building.
Cpi : internal pressure or internal suction.
F= (Cpe-Cpi)A X pd
Where Cpe : External presure Coefficient
Cpi : Internal pressure Co-efficient
A : Surface area of the structural element or cladding unit
pd : Design Wind Pressure.
Note :
For Symmetrical Buildings : Wind Loads are calculated in X & Y Directions.
It may be necessary to investigate the
forces due to wind from all directions.
For Unsymmetrical Buildings :
Page 1
Wind Analysis
Wind Data :
Location = MALKARAM
Wind zone = -
Basic Wind speed , Vb = 44 m/sec (33 to 55 m/sec)
Terrain category = 2
Class of Structure = A
Flat That is upward
= FOR k3 factor
Topography slope< 3 Deg
Life of structure = 100 Years
Design Wind Speed
Vz = Vb X K1 X K2 X K3
K1 = 1.07
K2 = Varies With height
K3 = 1
Vz = 44 X 1.07 X K2 X 1
Vz = 47.08 K2
Design Wind Pressure :
pd or pz = 0.6 Vz2
= 0.6 X 47.08 X 47.08 X K2 X K2
= 1329.92 K2 X K2 N/Sq.m
= 1.33 K2 X K2 Kn/m2
Elevation K2 K22 pz or pd (Kn/m2)
8.53 0.853 0.72761 0.968
7.62 0.762 0.58064 0.772
4.32 0.432 0.1866 0.248
3.3 0.330 0.1089 0.145
0 0.000 0.0000 0.000
Wind Load = 2.750 x 3.3
Frontal area of Room = 2.750 x 3.3 = 2.26875 Sq.m
4
Load = 2.26875 x 0.145 = 0.32857815 kn
Wind Load on each column = 0.968 x 0.3 = 0.29029762 Kn/m
Wind load on grid beams = 2.44 X 1.06 X 0.772 = 1.00
2
Load on security room = 2.75 x 3.3 x 0.150 = 0.3403125 Kn/m
2 2
Page 1
For K2 Refer Table 2 of IS:875-3
Category 1 : No obstructions available to the building e
Category 2 : coaststerrain
Open and flat
withtree
wellless Plainsobstructions
scattered where otherofst1
Category 3 : Refer to areaany
of closely spacedless
have heights buildings of heigh
than 1.5 m
Category 4 : Refer to area with highly closed buildings of large
Factor K2 also depends on the dimensions of the building under consideration.
The structures are classified as
Class A : max l,b,h :
Class B : max l,b,h :
Class C : max l,b,h :
For K3 Wind motion depends on topography of the area
if upward wind slope Theta <=3 :
Theta > 3 :
Step 1 : Design Wind Speed (Vz) :
Vz = Vb X K1 X K2 X K3
Where Vb = Basic Wind Speed
K1 = Risk Coefficient
K2 = Terrain height and structure siz
K3 = Topography Factor
Step 2 : Design Wind Pressure pz' (6.2.1)
The Design wind pressure at any height above mean Ground level shall be ob
pz = 0.6 Vz2
Where pz = Design wind Pressure in N/m2
Vz = Design wind speed in m/sec
Wind Loads on Buildings :
Wind Load : Net pressure acting on the surface and the surfac
Net Pressure : Algebraic sum of external and internal wind press
external pressure coefficient,depends on the dim
Cpe : and shape of the building.
Cpi : internal pressure or internal suction.
F= (Cpe-Cpi)A X pd
Where Cpe : External presure Coefficient
Cpi : Internal pressure Co-efficient
A : Surface area of the structural element or cladding
pd : Design Wind Pressure.
Note :
For Symmetrical Buildings : Wind Loads are calculated in X
For Unsymmetrical Buildings: It may be necessary to invest
forces due to wind from all di
available to the building ex : Sea
llless Plainsobstructions
scattered where otherofstructure if m height
1.5 m to 10
ely spacedless
e heights buildings of heights
than 1.5 m upto 10 m
ghly closed buildings of large heights
consideration.
<20 m
20 to 50 m
> 50 m
K3=1 Refer code
K3=1.0 to 1.36
asic Wind Speed
sk Coefficient
rrain height and structure size factor
pography Factor
ean Ground level shall be obtained by the
esign wind Pressure in N/m2 at height Z
esign wind speed in m/sec
on the surface and the surface area.
ernal and internal wind pressure acting on the surface.
oefficient,depends on the dimensions,roof angels
and shape of the building.
nternal suction.
tructural element or cladding unit
nd Loads are calculated in X & Y Directions.
t may be necessary to investigate the
orces due to wind from all directions.
Wind Analysis
DATA
Wind Basic Wind speed ,
Location Terrain category Class of Structure
zone Vb m/sec
HYDERABAD - 44 2 A
Topography for k3 factor Terrain Category Life of structure in years
Flat That is upward slope< 3 Deg 2 100
Design Wind Speed and Design Wind Pressure
K1 K2 K3 Vz pd or pz
Vb X K1 X K2 X K3 0.6 Vz2
Varies
1.07 With 1 47.08 K2 1.330 K2*K2
height
Final Wind Pressure
Elevation K2 K22 pz or pd (Kn/m2)
12.5 1.025 1.050625 1.397
11.5 1.015 1.030225 1.370
8.5 0.850 0.7225 0.961
5.5 0.550 0.3025 0.402
2.5 0.000 0.0000 0.000
