Reliable assumptions for structural fire design of steel car parks

PurposeThis study aims to analyze and discuss the key design assumptions needed for design of car parks in steel, to highlight the impact that the increased fire loads introduced by modern cars and changes in the fire dynamics have on the design, such as fire spread leading to non-localized fires.Design/methodology/approachIn particular, a reliable fire load density to be used for structural design of car park structures is assessed, based on investigations of the fire loads of modern cars. Based on knowledge of fire load and fire performance of cars, the consequences on the fire safety design of steel structures are presented.FindingsDesign recommendation about fire load density and fire protection of common steel profiles are given. Finally, the proposed design is compared with a design practice that has been applied in many instances for car parks constructed with unprotected steel, and recommendations for a reliable design process are provided.Originality/valueNumerous car park buildings have recently been designed of steel structures without passive or active fire protection. The key assumptions that makes possible such design are local fire scenarios, outdated values of the car fire load and utilization of the ultimate steel strength. This paper identifies the shortcomings of such key assumptions, indicating the need for revisiting the methods and possibly even checking the analyses carried out for some already-built car parks.