This is an explanation how to input wind load data in the warehouse with gable hip roof(Two-way).
Information of the example model is given as follows.
Figure1. Warehouse Example Model
The velocity pressure should be calculated in order to get the value of the wind load.
It usually applies ' 1.0 ' on the Ground Elevation Factor, Ke, if there is no exceptional case caused.
It applies ' 0.85 ' since the wind directionality factor is based on the structure.
Kzt = (1+K1K2K3)2
Assumed ValuesHill Type : 2S Escarpment
H = 20m, Lh = 40m, x = 40m → H/Lh = 20/40 = 0.5, x/Lh = 40/40 = 1.0
The following is a table that indicates the final value of the velocity pressure after calculating values for all variables. To calculate wind pressure, qh value for the roof level is applied.
Applying the pressure value depending on levels is more exact, but, it is okay to put the load value by using only the value of qh instead.
Velocity Pressure : qz = 0.613KzKztKdKeV2 ≈ 490N/㎡ =qh
p = qGCP - qi(GCpi)
Case 1) Wind Pressure = External Wind Pressure - Internal Wind Pressure (Positive)
Case 2) Wind Pressure = External Wind Pressure - Internal Wind Pressure (Negative)
Two coefficient values for external pressure and internal pressure are needed in order to satisfy the formula. Basically, wind pressure has two values depending on the direction of internal pressure. If internal pressure is larger than the external pressure, positive internal pressure is generated. In the opposite case, negative internal pressure is generated.
Wind ward wall, leeward wall, and side wall are needed to satisfy the calculation of external wind pressure.
The following is an explanation of the calculation for the x-direction and wall.
• Gust Factor (G) = 0.85 (Assumed Value)
* You can get the gust factor as per 26. 11. 4
• Wall Pressure Coefficients (Cp)
* L/B =14.4/ 18.6 = 0.774
q_wind = qzGCP = 490 * 0.85 * 0.8 = 333.2 N/m2
Blue Box : Wind load for Leeward wall (Wx(+ or -)_Leeward)
q_lee = qhGCP = 490 * 0.85 * - 0.5 = -208.3 N/m2
Yellow Box : Wind load for Side wall (Wx(+ or -)_Side)
q_side = qhGCP = 490 * 0.85 * - 0.7 = -291.6 N/m2
The following is an example of the calculation for the roof in X-Direction.
• Gust Factor (G) = 0.85 (Assumed Value)
* You can get the gust factor as per 26. 11. 4
• Roof Pressure Coefficients, Cp, for use with qh
Red Box : Wind load for windward roof (Wx(+ or -)_Windward)
q_wind = qzGCP = 490 * 0.85 * -0.392 = -163.27 N/m2
q_wind = qzGCP = 490 * 0.85 * -0.071 = -29.58 N/m2
Blue Box : Wind load for Leeward wall (Wx(+ or -)_Leeward)
q_lee = qhGCP =490 * 0.85 * - 0.6 = -249.94N/m2
The following is an example of the calculation for the roof in X-Direction for the side area.
• Gust Factor (G) = 0.85 (Assumed Value)
* You can get the gust factor as per 26. 11. 4
• Roof Pressure Coefficients, Cp, for use with qh
Red Box : Wind load for windward roof (Wx(+ or -)_Windward)
q_wind = qzGCP = 490 * 0.85 * -0.972(Apply Max.Cp)= -404.9 N/m2
q_wind = qzGCP = 490 * 0.85 * -0.18= -75.0 N/m2
Blue Box : Wind load for Leeward wall (Wx(+ or -)_Leeward)
q_lee = qhGCP =490 * 0.85 * - 0.6 = -249.94N/m2
The following is an explanation of the calculation for the y-direction. The wall pressure for the y-direction can be calculated as the x-direction way.
• Gust Factor (G) = 0.85 (Assumed Value)
* You can get the gust factor as per 26. 11. 4
• Wall Pressure Coefficients (Cp)
Red Box : Wind load for windward wall
q_wind = qzGCP = 490* 0.85 * 0.8 = 340 N/m2
Blue Box : Wind load for Leeward wall
q_lee = qhGCP = 500 * 0.85 * -0.3 = -127.5N/m2
Yellow Box : Wind load for Side wall
q_side = qhGCP = 500* 0.85 * -0.7 = -297.5N/m2
The following is an example of the calculation for the roof in Y-Direction.
• Gust Factor (G) = 0.85 (Assumed Value)
* You can get the gust factor as per 26. 11. 4
* h = 8.5m, Lx = 18.6m → h/L = 0.457
q_wind = qzGCP = 490 * 0.85 * -0.266 = -110.81N/m2
q_wind = qzGCP = 490 * 0.85 * -0.217 = -90.39N/m2
Blue Box :Wind load for leeward roof (Wx(+ or -)_Leeward)
q_lee = qhGCP = 490 * 0.85 * -0.6 = -249.94N/m2
• Roof Pressure Coefficients, Cp, for use with qh
Figure 21. Roof Pressure Coefficients
The following is an example of the calculation for the roof in Y-Direction for the side area.
• Gust Factor (G) = 0.85 (Assumed Value)
* You can get the gust factor as per 26. 11. 4
* h = 8.5m, Lx = 18.6m → h/L = 0.457
q_wind = qzGCP = 490 * 0.85 * -0.9 = -374.90N/m2
q_wind = qzGCP = 490 * 0.85 * -0.18 = -74.98N/m2
• Roof Pressure Coefficients, Cp, for use with qh
Figure 23. Side Roof Pressure Coefficients
Partially enclosed buildings in enclosure classification would be applied in this example. Therefore, the value of the internal pressure coefficient can be assumed as +0.55 and -0.55.
Wind pressure in the x-direction is given as follows. The values of each case in the wind pressure are calculated by applying the values of the external pressure and internal pressure.
The final values for cases 1 & 2 are as follows.
• Sign (+) : Direction to the inside of the building
• Sign (-) : Direction to the outside of the building
* Tips : you can easily distinguish each case if you put the name above.
Considered Factors
- Case : Case 1 & Case 2
- Wind Direction : X-Direction & Y- Direction
- Wind Sign : (+) & (-)
• Sign (+) : Direction to the inside of the building
• Sign (-) : Direction to the outside of the building
When inputting the wind load into the model, the sign must be corrected according to the direction of the load.
It also creates a floor load type for the opposite direction.
Table 9. Case 2 Values for Wall and Roof
• Sign (+) : Direction to the inside of the building
• Sign (-) : Direction to the outside of the building
When inputting the wind load into the model, the sign must be corrected according to the direction of the load.
It also creates a floor load type for the opposite direction.
Before performing analysis and design, we recommend you make load combinations with a wind load. Even if it is not automatically generated, you can easily create it by using a table for the load combination or copying it from excel.