A simplified analysis of catenary action in steel beams in fire and implications on fire resistant design

This paper describes the results of a numerical investigation of the large deflection behaviour of steel beams under fire conditions, taking into consideration the effect of catenary action provided by the surrounding structures. The main focus is on the development, validation and application of a simplified calculation method that may be adopted in design calculations. Because no experimental result is available for validation of the simplified calculation method, the finite element program ABAQUS has been used to simulate the large deflection behaviour of a number of steel beams so as to provide alternative results for validation of the proposed method. Utilising catenary action has the potential of eliminating fire protection to all steel beams without causing structural failure in fire. However, practical application of catenary action will be restricted by concerns over large beam deflection causing integrity failure of the fire resistant compartment and additional cost of strengthening the connections and the surrounding structures to resist the catenary forces in the steel beams. This paper will provide a discussion on practical implications of utilising catenary action in steel beams as a means of eliminating fire protection. A number of examples will then be provided to illustrate the type of steel framed structure that could benefit the most from exploiting catenary action in fire resistant design.