Effective seismic retrofitting concept for existing car park buildings in moderate seismic regions

Carparks are highly systematic and standardized building typologies. As enduser requirements are almost the same throughout Europe, carpark buildings can be easily categorized according to their geometry and structural system. Split‐level carparks are common practise, especially for city‐centre areas. However, their assembly includes some inherent disadvantages regarding the seismic performance. In the light of the new National Annex in Germany (DIN‐EN‐1998‐1/NA) the seismic performance assessment of existing buildings gains increasing importance in areas of low‐to‐moderate seismicity as well. This paper describes the assessment of the seismic performance of an existing multistorey carpark, built in Aachen (Germany) in the 1980s and proposes an efficient, low‐cost pre‐earthquake strengthening strategy. The investigated structure consists of steel‐concrete‐composite floors and concentrically‐braced frames (CBFs) in both longitudinal and transverse direction. Brace‐to‐beam/column connections represent the weak point of the structure, as their capacity is lower than the tensile/compressive resistance of the braces. An unconventional low‐cost retrofitting strategy by means of “weakening” the existing hollow‐section‐braces is investigated and discussed in this contribution.