Experimental and numerical modelling of intumescent protected flooring cellular steel beams subjected to extreme fire conditions

Abstract

National regulations require buildings to be stable for a specific period of time in fire. For steel beams, different standards provide limiting temperature tables for different load ratios. Designers must provide adequate fire insulations for steel elements to prevent their temperature from rising above limiting temperatures and hence maintain the stability of buildings. When it comes to perforated beams, no such tables exist. The standards for solid beams do not apply to perforated beams as they behave differently in fire. On a related note, offshore regulations provide a single limiting temperature for all steel members in hydrocarbon fire and do not account for the effect of the applied loads. This research, experimentally and numerically investigates the behaviour of intumescentcoated perforated composite beams exposed to cellulose and hydrocarbon fires under different load ratios. In doing so, it provides an understanding of the structural and thermal behaviour of coated perforated beams and determines their limiting temperatures for different load ratios in standard fire and their limiting temperatures in hydrocarbon fire. To begin with, four unloaded perforated and solid beams with different coating thicknesses in standard fire are examined numerically and experimentally. The results establish the influence of openings on the temperature rise of webs and the effectiveness of the coatings in mitigating this effect. Secondly, the structural performance of a composite perforated beam at room temperature is examined numerically. The Riks and the general static analysis are employed to simulate the local failure of the beam. A finite element model is developed. It is shown that the numerical results are in good agreement with experiments and that the general static analysis is more suitable in simulating the behaviour of beams with local web failure. Next, three loaded and intumescent protected perforated beams are investigated numerically and experimentally. The numerical models are comprised of heat transfer and structural analyses. To estimate the experimental beam temperature in the model, the coating surface is exposed to a standard fire. The validity of numerical model and its results is established as they agree with the experimental outcomes. A comprehensive parametric study is then conducted to define the limiting temperature for the three beams mentioned above. The applied load ratios are changed from 10% to 85% of the ultimate load of the beams. It is shown that the limiting temperatures for load ratios below 30% is around 750°C and it reduces to 450°C by increasing the load ratio to 85%. Finally, protected perforated beams exposed to hydrocarbon fire are modelled. The thermal load of the three beams is altered from standard to hydrocarbon fire. It is shown that the limiting temperature of perforated beams in hydrocarbon fire is slightly higher than that of standard fire. This is considerably higher than current limiting temperatures in offshore regulations. The findings of this research could lead to reductions in costs as well as the weight of offshore facilities.

Date of Award	2018
Original language	English
Supervisor	Faris Ali (Supervisor) & Ali Nadjai (Supervisor)