Application of a generalised engineering methodology for thermal analysis of structural members in fire

Abstract

The GeniSTELA code has been developed as a generalised CFD-based approach for thermal analysis of protected steelwork in fire. This is a quasi-3D approach with computation of a "steel temperature field" parameter in each computational cell. The methodology accommodates both uncertainties in the input parameters and possible variants to the specification by means of simultaneous calculations. A framework for the inclusion of temperature/time-dependent thermal properties, including the effects of moisture and intumescence, has been established. GeniSTELA has been implemented as a submodel within the SOFIE RANS CFD code. This paper presents the full-scale application of the method for two full-scale scenarios: standard tests in fire resistance furnaces and the post-flashover BRE large compartment fire test. Comparison with test results permits model validation whilst model capabilities are demonstrated by simultaneous calculations for consideration of a range of parameters of interest, including member size and protection material properties. The computational requirements are also addressed, with the efficient use of the method being assessed considering aspects such as number of parametric variants and the frequency of GeniSTELA call compared to flowfield solution, i.e. the balance between fluid and solidphase analyses. The results enable identification of the critical parameters which affect the thermal performance. Ultimately, the steel temperature field prediction provided by GeniSTELA provides far more flexibility in assessing the thermal response of structures to fire than has been available hitherto, demonstrating the potential practical use of the method.