How to perform wind comparison

This guide described the procedure for VIIA workflows to execute the seismic assessment of a structure based on a comparison with the wind loads. In EN1998-1 the code allows for certain building structures to verify the seismic design situation calculated is lower than that due to the other relevant action combinations for which the building is designed on the basis of linear elastic analysis. Refer to art. 4.4.1 (2) of EN1998-1:2004.

To use this approach for a building structure, discuss the importance factor and regularity of the building structure with the lead engineer before proceeding.

In VIIA we often encounter building structures for which the original wind design is not available. In the workflow in this guide we assess based on the highest wind load that has occurred on the structure in the past. Note that the relevant load bearing structure was present at that time (this is important when the load-bearing structure was subject of larger modifications). In other situations the original year of building is considered.

Note

Automation for this procedure has been implemented for the wind part of the comparison, and generates the values in the Haskoning template. User should analyse the seismic part and provide the report in NCG template. Developments in the future will further automate the workflow.

The procedure is based on the maximum highest hourly average wind speed over the lifetime of the structure. The wind load is retrieved from the Royal Netherlands Meteorological Institute KNMI for weather station of Eelde.

The EN1991-1-4 is used to calculate the wind loads. This approach is based on the basic wind velocity. This requires to convert the measured values to the value required for the Eurocode. For this the maximum highest hourly average wind speed is determined during the lifetime, based on measurements of the weather station Eelde. The fundamental value of the basic wind velocity is the characteristic 10 minutes mean wind velocity, irrespective of wind direction and time of year, at 10m above ground level in terrain category II. The measurements in Eelde are at 10m above ground level and is situated in terrain category II. The site is expected to be representative for the average location in Groningen, or conservative. It is assumed that the ratio between 10-minute and hourly average wind speed is 1.10. Conservative estimation based on literature.

To assist the structural engineer with the assessment, the following script can be used to generate a report with the values that can be used in the comparison. This includes determining the relevant wind load, the interpolation of the wind factors on the roof and facades and the calculation of the total value, based on the different loading zones.

# Start project and collect data from MYVIIA
project = viia_create_project(project_name='S1234')

# Execute wind comparison
project.viia_wind_comparison(height=11, width=10, depth=10, year=2010, roof_type='duopitch', roof_angle=32.4)

The values in the report can be used to execute the comparison. As the tool itself is not yet validated, please check the results.

In the VIIA knowledge sharing meeting of January 2026 this procedure was presented. You can find the presentation slides here.