The influence of changes in the applied wind load since TGB 1955 on existing buildings for additional layers

Abstract

The Netherlands is facing a housing crisis, with a growing shortage due to urbanization and limited available land. An alternative for constructing new buildings is adding levels to existing buildings, but this poses challenges in ensuring structural stability, particularly as existing buildings were designed with older design codes, while new levels must comply with the latest Eurocode. However, an overview of the exact changes in wind loads and what kind of influence this has on adding new levels to an existing building is missing. Additionally, it is unknown what the exact gap is between the building or location specific wind load and the wind load according to the design codes. This research aims to clarify how changes in wind load design codes affect adding levels to existing buildings.
The study analyses the development of design codes from TGB 1955 to the Eurocode, focusing on wind loads. Wind pressure and pressure coefficients are examined through KNMI data and computational fluid dynamics (CFD) simulations. Findings suggest that while overall wind speeds align with design codes, certain coastal locations like Hoek van Holland and Vlissingen show deviations, indicating a need to revise the wind area map. Additionally, pressure coefficients are not constant over building surfaces. Especially the width seems to have an influence and this parameter not considered in the current Eurocode.
Adding levels to an existing building influences the wind load in a twofold manner: extra surface subjected to wind load and a difference in design codes for wind load between the now and past. The structure of the existing building must be used optimally to support the added levels. A case study on the SCYE010 building demonstrates that optimizing the top level's design and geometry can reduce wind pressure and loads, emphasizing the importance of code evolution in such projects. These findings offer critical insights for designing additional levels on existing structures.