A sample calculation done for determination of wind load according to BS6399:1997 to a rectangular building. This document determines the wind load va...
1 since this building is a framed structure with structural walls
Building Height above ground level = 20 m <300 ; within limits 0.035 <0.25 Dynamic Augmentation Factor = Cr = ; within limits So the assessment of the wind load to this structure is within the scope of the code Choice of Method For majority of simple rectangular shaped building it will be sufficient to use standard method of calculating wind loads with four orthogonal cases. Other than that the code restrict that it must only be used only for UK cli mate condition. So expecting of higher accuracy of using directional method is meaningless So Standard Method of analysis is used
Wind Loading is within the scope of the code
Standard Method is used
Determination of Site Wind Speed Site Wind Speed
=
Altitude Factor Sa Site Contour Map Figure 7
Distance to the Sea = 0.9 km; Altitude of the Site = 4.2 m MSL So Upwind Slope = 4.2/900 = 0.005 <0.05 Hence Topography is not significant
Topography is not significant
DS =
4.2 m Sa = 1 + 0.001xDS
Clause 2.2.2.4
=
1 + 0.001x4.2
=
1.004
Seasonal Factor Ss Since this structure is permanent and exposed to wind for continuous period of more than 6 months Ss = 1 Probability Factor Sp Since partial safety factors are used based on BS 8110 part 01 to the wind load; Sp = 1 Sp = 1.0 Directional Factor, Site Wind Speed, Terrain and building Factor and Effective Wind Speed For the consideration of the directional factor, Four orthogonal wind directions are selected as follows
Building Contour Map
There are four faces consider for the wind analysis NE FACE = Building Face along Grid Line 4 SE FACE = Building Face along Grid Line G SW FACE = Building Face along Grid Line 1 NW FACE = Building Face along Grid Line A
Figure C1
PROJECT STRUCTURE CODES Reference
ELEMENT BS 6399:2 1997 Corrigendum No. 1
DESIGNED BY
Wind Load Calculation CHECKED BY
Calculations
For the determination of the Effective height, Adjacent Building located around the site are as follows Google Earth
1 STOREY BUILDINGS NEARBY
Figure C2
Figure C3
REF 1/24/2017 Output
PROJECT STRUCTURE CODES Reference
ELEMENT BS 6399:2 1997 Corrigendum No. 1
DESIGNED BY
Wind Load Calculation CHECKED BY
Calculations
REF 1/24/2017 Output
The closest distance to the sea and the closest distance in town parameters are required for the determination of the terrain and building factor Sb. The Colombo boundary is selected town. Those parameters are marked in the following figure Google Earth
The applied average values are calculated based on Eq 1 & Eq 2 One sample calculation for joint load at X direction at roof level Mz = 0.59 Ax 2 Fzx = 1.25x0.59 x28.3x3.2x0.5 = 19.7 kN This applied value can be found in the model in section 3.3.2. Similarly for all other levels in both directions are calculated and summary of loads are as follows Level RF 4F 3F 2F 1F GF
Fzx kN 19.7 35.5 34.4 29.2 25.6 16.4
Fzy kN 2.78x2 5.0x2 4.86x2 4.18x2 3.61x2 2.32x2
Figure C4 The wind load for different four directions are tabulated in the following Table
Clau. 1.7.3.3. Table 4 HB-Wind Loading by Nicholas J. Cook HB-Wind Loading by Nicholas J. Cook Figure C3 & Table 3 of BS 6399:2 BS 6399:2 Clau 2.2.2.1. Clau 2.2.3.1. Clau 2.1.2.1.
