calculation of wind forces on buildings
TRANSCRIPT
Reference Calculation Output
Wind load calculations:
Local Standard For post disaster , wind zone -3 area, for wind Basic wind speed = 38m/sTable 3-1
CP-3 Chapter v
Topography factor S1 = 1Statistical factor S3 = 1
Ground roughness factor S2:Ground roughness : Class 4 (Surface with large and frequent
obstructions)Building class : B ( Neither the greatest horizontal dimension nor the
greatest verticle dimension exceeds 50m.)
Local Standard For Sri Lankafor wind
CP-3 Chapter v b= 30.55 m l/w = 30.55/24.1Table 10 l= 30.55m = 1.27
d= 24.1mw= 24.1m b/d = 30.55/24.1
= 1.27
height/ breadth = 40/24.1= 1.66= 0.98
Specimen calculation for First floor level:
Height = 4.7mHence S2 factor = 0.55
= 38x1x0.55x1= 20.9 m/s
q =
= 257.7F = 0.98x257.7x(3.5x5.9)
= 5.21kN
Similarly wind forces at every floor level could be calculated.
Project : Dahampaya Feature Frame Analysis
DESIGN UNIT Designed Date
Vs= Vx S1 x S2 x S3
Dynamic pressure of the wind (q) = K.Vs2
K=0.59 N/m2
Wind force (F) = Cf . q. Ae
Force coefficient (Cf)
Cf
Vs
0.59x(20.9)2
N/m2
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Reference Calculation Output EPC DIVISION Checked Date
CENTRAL ENGINEERING CONSULTANCY BUREAU Job Code D-676 Page 04 of 08
Wind forces at roof:
CP-3 Chapter vTable 8
h/w = 1.66 ( 3/2 <(h/w)<6)
Cpe facotrs for the roof
Appendix E Assume four faces equally permeable Cpi = 0.3
(Cpe- Cpi) factors
Wind force on roof "A" == 5.05 kN
Wind force on roof "B" == (-10.1) kN
θ
Resultant horizontal force at roof ( R ) = += 10.36kN
HorizontalThe calculated wind forces for the frame could be summarized as force from rooffollows. = 10.4kN
Project : Dahampaya Feature Frame Analysis
DEC
Pressure co-efficents Cpe for pitch roofs:
Roof pitch 40 ْ
The critical condition applies to the frame, when α=0 ْ
Wind force (F) = (Cpe- Cpi). q. Ae
0.1x604.2x (9.152)
(-0.2)x604.2x (9.152)
5.05 cos 40° 10.1sin 40°
-0.2 -0.5
A B
0.1 -0.2
A B
5.05kN 10.1kN
Reference Calculation Output DESIGN UNIT Designed Date
EPC DIVISION Checked Date
CENTRAL ENGINEERING CONSULTANCY BUREAU Job Code D-676 Page 05 of 08
Floor Level H q F(m) (m/s) (KN)
Ground 1.2 0.52 19.76 230.4 17.4 3.93
First 4.7 0.55 20.9 257.7 20.65 5.21
Second 8.2 0.59 22.4 296 20.65 5.99
Third 11.7 0.63 23.94 338.1 20.65 7
Fourth 15.2 0.69 26.22 405.6 20.65 8.2
Fifth 18.7 0.73 27.74 454 20.65 9.19
Sixth 22.2 0.77 29.26 505.1 20.65 10.22
Seventh 25.7 0.8 30.4 545.2 25 13.3
Eighth+roof 30.7 0.84 32 604.2 14.75 8.7 + 10.4= 19.1
Frictional Drag:
h = Height to the eaves = 40m
b = Dimension normal to wind = 30.55m
d = Dimension in wind direction = 24.1m
d/h = (24.1/40) = 0.6 < 4
d/b = (24.1/30.55) = 0.8 < 4
Frictional drag is not neccesary.
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S2 Vs Ae
(N/m2) (m2)
Reference Calculation Output
Project : Dahampaya Feature Frame Analysis
DESIGN UNIT Designed Date
EPC DIVISION Checked Date
CENTRAL ENGINEERING CONSULTANCY BUREAU Job Code D-676 Page 06 of 08
Notional Horizontal loadSpecimen Calculation of Notional horizontal loads for frame 7 (A-K):
Consider first floor level:Weight of beams = 135.3kN(0.3x0.375x(20+26.85)x24) +(0.225x0.4x4.1x24)
Weight of slab = 418kN(0.15x24x(47.2+14.6) +(0.175x24x5.9x7.5) + (0.125x24x2x1.6)
Weight of finishes = 109.3kN(1x(91.5+14.6+3.2))
Weight of Brick walls = 318.3kN(5.2x2.95x(5.9+2.65+8.6+3.6))
Weight of Columns = 112.5kN(0.5x0.5x24x3.5x5)+(0.3x0.3x24x3.5)Total = 1093.4kN
Therefore Notional horizontal load at First Floor level = 0.015x 1094 kN Notinal Load
= 16.4kN = 16.4 kN
Simillarly Notional load for other floor levels also calculated.
Comparison of Horizontal loads:
Floor level Wind Force NHLKN
Ground 3.9 4.68 5.5 24
1 5.2 6.24 7.3 16.4
2 6 7.2 8.4 16.4
3 7 8.4 9.8 16.4 Notional loads
4 8.2 9.84 11.5 16.4 Critical
5 9.2 11.04 12.9 15
6 10.2 12.2 14.3 15
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1.2Wk 1.4Wk
Reference Calculation Output7 13.3 16 18.6 16 Wind
loads8 20.3 24.4 28.5 18.5 Critical
Project : Dahampaya Feature Frame Analysis
DESIGN UNIT Designed Date
EPC DIVISION Checked Date
CENTRAL ENGINEERING CONSULTANCY BUREAU Job Code D-676 Page 07 of 08
After finding verticle and horizontal loading for the frame, frame analysis was done using "Etab" software.Relevant Input and output files are attached here with.
DEC
Reference Calculation Output
Project : Dahampaya Feature Frame Analysis
DESIGN UNIT Designed Date
EPC DIVISION Checked Date
CENTRAL ENGINEERING CONSULTANCY BUREAU Job Code D-676 Page 08 of 08
DEC
1.267634855
1.659751037
1.267634855
1.659751037
Notional
Reference Calculation Outputs
Project Feature DESIGN UNIT Designed Date
DEC
EPC DIVISION Checked Date CENTRAL ENGINEERING CONSULTANCY BUREAU (CECB) Job Code Page of
DEC