Modelling real fire by FDS and 2-zone model for structural post-fire assessment

Abstract

Post-fire resistance assessment of industrial structures is of prime importance to companies having to deal with such accidental situations. Most of the time, the structure or at least a major part of it still stands. Being able to quickly assess the temperature it was once submitted to, is very important to reevaluate its load-bearing capacity. The latter is to help take wise decisions regarding its dismantling or replacement and to avoid unnecessary delays during which the industry can no longer carry out its business. This paper describes a quick methodology to do so and demonstrates its accuracy with a case-study. Although full-scale fire experiments are reported in the literature, they are mostly under-instrumented, in such a way that few information is usually available. However, in 2018, a full-scale and fully instrumented fire experiment was conducted by Tongji university on a steel frame single-story building. This case study is simulated in the present paper using two different numerical simulation techniques, namely 2-Zone model using Ozone and Computational Fluid Dynamics using Fire Dynamics Simulator (FDS). Through the FDS model, several features of the test can be thoroughly modeled to increase the accuracy of the results, however increasing the calculation time. While the 2-Zone model delivers quick and accurate results (time versus temperature development) especially if the model can be calibrated by the use of tests or based on visual observations reported by the fire brigade during the fire.