# Wind Loads on High Building

## Technical Article on the Topic Structural Analysis Using Dlubal Software

### Technical Article

The following study compares the wind pressure on a high building obtained by RWIND Simulation with the results published by Dagnew et al. at the 11th Americas Conference on Wind Engineering in June, 2009. In this paper, the Commonwealth Advisory Aeronautical Council (CAARC) building is used as a model, and the results of several different numerical methods are compared with experimental data obtained from wind tunnels.

The RWIND Simulation program is primarily designed to quickly calculate results even for relatively complex and large models. Default settings were used for a quick calculation, which subsequently took only 5 minutes on a standard PC. The results obtained are in relatively close agreement with those published in the above article [1], and are discussed in more detail below.

#### Computational Domain and Mesh

The CAARC building is a rectangular prismatic shape with dimensions of 150 ft by 100 ft by 600 ft in height. The wind tunnel dimensions are 4,950 ft in the streamwise direction, 3,000 ft in the spanwise direction, and the total height is equal to 1,200 ft.

The finite volume mesh was locally refined near the building model with the total number of mesh cells at 540,180. Although RWIND Simulation allows calculations on significantly finer meshes (up to 50 million cells), a relatively coarse mesh was selected for a quick calculation.

#### Simulation Setup

The simulation parameters and the inlet wind velocity profile are defined according to Dagnew et al. [1], and are displayed in Image 02.

The model boundary conditions are described in Table 1.

ParametersTop, Left, and Right FacesInletOutletBuilding Walls and Ground
Turbulence Intensity-0.15%--

The k‑epsilon turbulence model was used, and the inlet turbulent intensity was set to 0.15%.

#### Calculation

The calculation was performed with the RWIND Simulation Solver, which is relative to the OpenFOAM-SIMPLE family of solvers. It is a steady-state solver for incompressible, turbulent flow. The entire simulation, including mesh generation and result preparation, was completed in 5 minutes on a PC with 8 cores (Intel i9‑9900K). The residual pressure convergence criterion was set to 0.001, which is the standard value for the quickest calculation, and was achieved after 350 iterations. The minimum residual pressure is 0.0001, and it could be reached after 700 iterations while continuing the calculation. However, the results were not significantly affected.

#### Results

Image 05 trough Image 07 show the pressure distribution on the building surface and the velocity field. For validation and comparison purposes, the calculated pressure coefficient cp is compared to the data obtained from [1] in Image 9 trough Image 11. The cp coefficient is calculated as follows:

$$cp = p - p∞12 · ρ · vH2$$

The RWIND Simulation results and experimental results according to Dagnew et al. [1] on the windward face are in close comparison. On the sidewall and leeward faces, 10% - 20% differences between the measured and the calculated data are observed, which can be explained by the turbulence model (k-epsilon) used and the coarse computational mesh. The result accuracy can be improved by using more accurate turbulence models (LES), which will be available in future versions of RWIND Simulation.

RWIND Simulation Results:

Comparison with the data and results published in [1]:

#### Dipl.-Ing. (BA) Andreas Niemeier, M.Eng.

Mr. Niemeier is responsible for the development of RFEM, RSTAB, and the add-on modules for tensile membrane structures. Also, he is responsible for quality assurance and customer support.

#### Reference

 [1] Dagnew, A. K., Bitsuamalk, G. T., & Merrick, R. (2009). Computational evaluation of wind pressures on tall buildings. 11th Americas Conference on Wind Engineering | International Association for Wind Engineering.

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• Updated 11/09/2021

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