4.10. Computing Wind Loads on Building Components and Cladding

Problem files

weuq-0019/

This examples demonstrated a workflow for evaluating component and cladding loads on buildings. The geometry of the building used for this study is a gable roof low rise building taken from Tokyo Polytechnic University (TPU) aerodynamic database. Fig. 4.10.1 shows the study building in the CFD model. The STL geometry of the building can be found here that can be imported to the workflow. Most of the input parameters used in this example are similar to the example in Section 4.7.

Fig. 4.10.1 Study building with definition of the components.

In this example, the simulation is conducted in model-scale. The geometric and flow properties are given in Table 4.10.1. Please refer to the detailed CFD-based workflow in Workflow.

Table 4.10.1 Import parameters needed for the wind load calculation

Parameter	Description	Value	Unit
\(B\)	Building width	24.0	m
\(D\)	Building depth	16.0	m
\(H\)	Building eave height	8.0	m
\(\lambda_L\)	Geometric scale	1:100
\(\lambda_V\)	Velocity scale	1:3.0
\(\lambda_T\)	Time scale	1:33.33
\(H_{ref}\)	Reference height (mean roof height)	8.8	m/s
\(U_H\)	Reference mean wind speed (model-scale)	7.14822	m/s
\(T\)	Duration of the simulation (model-scale)	19.0	s
\(\theta\)	Wind direction	90.0	degrees
\(z_0\)	Aerodynamic roughness length in (full-scale)	0.30	m
\(\rho_{air}\)	Air density	1.225	kg/m^3
\(\nu_{air}\)	Kinematic viscosity of air	\(1.5e^{-5}\)	m^2/s
\(f_{s}\)	Sampling frequency (rate)	500	Hz

The upwind condition chosen for this example is open exposure type with aerodynamic roughness length of \(z_0 = 0.3\) m for wind direction \(\theta = 90^o\). To represent the effect of the upcoming terrain a turbulent inflow boundary condition is adopted at the inlet.

4.10.1. Workflow

The input to the whole workflow can be found in a JSON file here

In this example, the overall workflow is demonstrated by introducing uncertainty in the design wind speed. The user needs to go through the following procedure to define the Uncertainty Quantification (UQ) technique, building information, structural properties, and CFD model parameters.

Note

This example can be directly loaded from the menu bar at the top of the screen by clicking “Examples”-“E10: Computing Wind Loads on Building Components and Cladding”.

4.10.1.1. UQ Method

Specify the details of uncertainty analysis in the UQ panel. This example uses forward uncertainty propagation. Select “Forward Propagation” for UQ Method and specify “Dakota” for the UQ Engine driver. For specific UQ algorithms, use Latin Hypercube (“LHC”). Change the number of samples to 500 and set the seed to 101.

Fig. 4.10.1.1.1 Selection of the Uncertainty Quantification Technique

4.10.1.2. General Information

Next, in the GI panel, specify the properties of the building and the unit system. For the # Stories use 2 assuming a floor height of approximately 4.0 m. Set the Height, Width and Depth to 8.8, 24.0 and 16.0 with a Plan Area of 384.0. Define the units for Force and Length as “Newtons” and “Meters”, respectively.

Fig. 4.10.1.2.1 Set the building properties in GI panel

4.10.1.3. Structural Properties

Please leave the SIM panel of the workflow as it is, this example does not involve any structural analysis.

4.10.1.4. CFD Model

To set up the CFD model, in the EVT panel, select “CFD - Wind Loads on Isolated Building” for Load Generator. Detailed documentation on how to define the CFD model can be found in the user manual.

1. Specify the path to the case directory in Start tab, by clicking Browse button. Use version 10 for Version of OpenFOAM Distribution.

Fig. 4.10.1.4.1 Setting up the case directory and OpenFOAM version in the Start tab

2. In the Geometry tab, first set the Input Dimension Normalization to Relative to put the size of the domain relative to the building height. For Geometric Scale of the CFD model use 100.0 as the simulation is conducted at model scale. Set the Shape Type to Complex and import the building geometry by clicking Import STL from here. Set the Wind Direction to 90.0 to simulate wind incidence normal to the building width. See Fig. 4.10.1.4.2 for the details.

Fig. 4.10.1.4.2 Defining the domain dimensions and the building geometry.

2. Define the computational in Mesh tab with Background Mesh, Regional Refinements, Surface Refinements, Edge Refinements and Edge Refinements as shown bellow.

   

   Fig. 4.10.1.4.3 Define the computational grid in the Mesh tab

   

   Fig. 4.10.1.4.4 Create regional refinements

   

   Fig. 4.10.1.4.5 Create surface refinements

   

   Fig. 4.10.1.4.6 Apply further refinements along the building edges

   Run Mesh

   To generate the computational grid with all the refinements applied, click the Run Final Mesh button in the Mesh tab. Once meshing is done, in the side window, the model will be updated automatically displaying the generated grid.

   

   Fig. 4.10.1.4.7 Breakout View of the Mesh

4. To define initial and boundary conditions, select Boundary Conditions tab.

   • Based on the values given in Table 4.10.1, set the boundary conditions as shown in the following figure. Here the Wind Speed Scaling Factor is defined as a random variable and the uncertainties will be propagated in the wind load calculation. At the Inlet of the domain use TInf with the specified inflow generation method (DFM). Then, select Table for the Wind Profile and import the wind characteristics from here

   

   Fig. 4.10.1.4.8 Setup the Boundary Conditions

5. Specify turbulence modeling, solver type, duration and time step options in the Numerical Setup tab as shown bellow.

Fig. 4.10.1.4.9 Edit inputs in the Numerical Setup tab

6. Monitor wind loads from the CFD simulation in the Monitoring tab. Leave this tab options as shown bellow.

   

   Fig. 4.10.1.4.10 Select the outputs from CFD in the Monitoring tab

4.10.1.5. Finite Element Analysis

Please leave this panel to the default values, since no structural analysis is needed. We are mainly interested in evaluating wind loads on components and cladding.

4.10.1.6. Engineering Demand Parameter

Next, specify Engineering Demand Parameters(EDPs) in the EDP panel. Select Component and Cladding EDP option which allows the user to define the geometry of components. In the current workflow this is done using JSON file, which is provided in here.

Fig. 4.10.1.6.1 Select the EDPs to measure

Once specifying the path to this file in Component Geometry JSON Path, click Map Component Geometry onto Building Surface. This will map the comonent geometries on to the building surface as shown in the following figure.

Fig. 4.10.1.6.2 Map components to the building geometry.

4.10.1.7. Random Variables

Since the wind speed scaling factor is defined as a random variable, it will show up this panel. Now for the radom variable wsF set Normal for its probability Distribution with \(1.0\) Mean value and \(0.2\) Standard Dev.

Fig. 4.10.1.7.1 Define the Random Variable (RV)

4.10.1.8. Running the Simulation

The CFD simulation for this example is already run, and results are collected. The users can run the remain part of the workflow locally by clicking RUN button.

4.10.1.9. Results

Once the example is run, the results will aromatically show up . Then, the results will be displayed in the RES tab. The responses qualitative reported for Standard EDP include statistics of floor displacement, acceleration and inter-story drift, e.g.,

• 1-MP-zone1: represents mean pressure on a cladding/component element named zone1

• 1-RP-zone2: represents root-mean-square pressure on a cladding/component element named zone2

• 1-PP-zone1: represents peak pressure on a cladding/component element named zone1

• 1-MF-dr1: represents mean force on a component element named dr1

• 1-RP-wd1: represents root-mean-square force on a component element named wd1

• 1-PF-wd1: represents peak force on a component element named wd1

The Summary tab of the panel shows the four statistical moments of the EDPs which include Mean, StdDev, Skewness and Kurtosis.

Fig. 4.10.1.9.1 Summary of the recorded EDPs in RES panel

By switching to the Data Values tab, the user can also visualize all the realizations of the simulation. The figure below shows the variation of the peak pressure variation with the wind speed used in the simulation.

Fig. 4.10.1.9.2 (scatter-plot) Peak pressure vs wind speed, (table) Report of EDPs for all realizations

Franke2007

Franke, J., Hellsten, A., Schlünzen, K.H. and Carissimo, B., 2007. COST Action 732: Best practice guideline for the CFD simulation of flows in the urban environment.