Fire protection of composite beams with large web openings is an important design issue, especially when using intumescent coatings. This is due to higher web slenderness and differential thermal heating through the web openings in fire. Previous tests on composite beams, however, have involved simple support conditions and were performed under a standard fire temperature–time regime.
As performance-based design of fire-protected steel structures becomes more prevalent, it is important to investigate the behaviour of protected beams with web openings in complete frames under natural fires. This paper outlines the technical background before considering the development of more realistic performance within the design of optimised fire-protection systems of composite floor plates.