VE0310 | Eurocode Rectangular Cuboid – Wind Pressure Calculation Using Cp,1 and  Cp,10

Description

In the current validation example, we investigate wind pressure value for both general structural design (C_p,10) and cladding or façade design (C_p,1) of EN 1991-1-4 rectangular plan buildings. [1]. There are three-dimensional cases that we will explain more about them in the next part.

Finding the most accurate and compatible configurations regarding input data, such as turbulence models, wind velocity profiles, turbulence intensities, boundary layer conditions, order of discretization, and other factors, is one of the key aspects of CFD simulation. The important point is the Eurocode does not cover the required information for numerical simulation, such as CFD simulation. We provided here compatible RWIND settings in relation to the example of Eurocode cubic shape. Several formulas and diagrams are used for the static calculation of wind load, which is demonstrated in the following sections.

Analytical Solution and Results

There are three dimensional categories for rectangular cuboid due to the ratio of h/d as shown in figure 1 (EN 1991-1-4 Table 7.1). The input data and assumptions for each dimensional case are illustrated in the next part.

Figure 1: Rectangular Cuboid Dimensional Categories in Eurocode

For the first case (figure 2), the high-rise rectangular plan building (h/d=5) is considered regarding the defined zones (figure 3) for each elevation and input data. Also, the terrain category two is considered to create wind velocity and turbulence profile, which is shown in the following table; at the same time, constant values of turbulence intensity are investigated to calculate wind pressure values.

Figure 2: High-Rise Rectangular Cuboid Shape (h/d=5)

Figure 3: Zones Defining for Each Elevations of High-Rise Rectangular Cuboid

The results of the wind pressure value for C_p,1 and C_p,10 are obtained regarding different zones, dimensional ratios, and turbulence intensities. For the first case, which is high rise cube shape (h/d=5), the results are shown in figure 4 and 5. The results show that there is a good agreement when the real or high turbulence profile (such as 25%) is considered.

Figure 4: Wind Pressure Value for Different Zones Based on Cp,1 and Cp,10 (Case h/d=5)

Figure 5: Wind Simulation Results for 25% Turbulence Intensity and Real Turbulence Profile in Eurocode (Case h/d=5)

For each zone, it is possible to obtain a maximum pressure value which can be equivalented wind pressure value using Cp,1 for cladding or façade design, and an average pressure value which can be equivalented wind pressure value using Cp,10 for general structural design (figure 6).

Figure 6: How to Get Average and Maximum Wind Pressure Values for each Zone in RWIND

For the next case, middle-rise rectangular plan building (h/d=1) is considered regarding the input data and defined zones (figure 7 and 8), which are shown in the following picture and table:

Figure 7: Middle-Rise Rectangular Cuboid (h/d=1)

Figure 8: Defining Zones and Wind Direction for Middle-Rise Rectangular Cuboid (h/d=1)

For the second case, which is the middle rise cube shape (h/d=1), the value of C_p,10 and C_p,1 are demonstrated in the figure 9, 10. The results show that there is a good agreement when the real as well as high turbulence profile (such as 25%) is considered.

Figure 9: Wind Pressure Value for Different Zones using Cp,10 (Case h/d=1)

Figure 10: Wind Pressure Value for Different Zones Based on Cp,1 (Case h/d=1)

Figure 11: Wind Pressure Value for Different Zones Based on Cp,1 and Cp,10 (Case h/d=1)

For the last case, short-rise rectangular plan building is considered (h/d=0.25) regarding the input data and defined zones (figure 11 to 13), which are shown in the following pictures and table:

Figure 12: Short Rise Rectangular Cuboid (h/d=0.25)

Figure 13: Defining Wind Zones and Direction for Low Rise Cube (h/d

For the last case, which is a low-rise rectangular plan building (h/d=0.25), the value of C_p,1 and C_p,10 are shown in the figure 14 to 16. The results show that there is the good agreement when the real or high turbulence profile (such as 25%) is considered.

Figure 14: Wind Pressure Value for Different Zones using Cp,10 (Case h/d=0.25)

Figure 15: Wind Pressure Value for Different Zones Based on Cp,1

Figure 16: Wind Pressure Value for Different Zones Based on Cp,1 and Cp,10 (Case h/d=0.25)

Conclusion

The results show a good agreement for both general structural designs (C_p10) and cladding or façade design (C_p1) of rectangular plan buildings. Based on the results, generally, the recommended value of turbulence intensity is better to consider as a real Eurocode turbulence profile or choosing higher values (such as I=25%) for different zones and dimensional ratios. It can be seen by increasing the height of the rectangular cuboid and Reynolds numbers of the flow, the results would be more accurate. So specially for high-rise structures, we can expect very good predictions for wind pressure calculation for general structural and façade design.

Also, the rectangular cuboid model with recommended settings is available to download here:

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Eurocode Cube Shape – Verified Wind Pressure Value (with Cp,10 and Cp,1)