Impact of high-rise morphology on gas temperatures during fires
With the development and use of fire sensitive construction materials and furnishings,and with the growing demand for high-rise development, there is an increasing need forimproved fire safety measures. Modern high-rise policies within the UK and USArequire a minimum fire safety standard. Current techniques employed to achieve thiswhich includes performance based approaches are the "passive" built-in approach e.g.compartmentation etc, and "active" approach e.g. Sprinklers etc. Considering thediversity of building morphologies of modern high-rises buildings made possible byimproved construction techniques and materials, this research investigates thepossibility of the building morphology becoming an additional consideration in the"passive" strategy for high-rise fire protection. The focus of this research is ongas/atmospheric temperatures while proposing the smoke element as a subject forfuture studies. The aim of this study is to explore the impact of the morphology(geometry) of a "central core" high-rise floor on fire within a real life context withfocus on peak gas temperatures and its development during the fire growth stages. Inorder to achieve this aim, a set of objectives were developed based on critical analysisof existing literature. To reduce the scope of work the study focuses on central corehigh-rise types.The research methodology adopted for this study was based on the need for acontextual approach resulting in a robust ontological standpoint. To achieve theresearch aim, the study was designed to have an exploratory positivist experimentalapproach set within an interpretivist real life context. The case study method wasselected to meet the contextual and in-depth requirements of this study. Due to theimpracticality of erecting and burning a high-rise building for fire data extraction, thecase study was divided into two phases; a descriptive and exploratory phase to providethe contextual physical and thermal information respectively. Descriptive data wasextracted from selected real high-rise buildings and multiple case methods which consisted of World Trade Centre New York and One Canada Square London wereadopted for data triangulation. The two cases were selected for their morphologicaldisposition and the extent to which they represent the wider high-rise population. Twoadditional morphologies selected from survey statistics were generated which resultedin four morphological cases used in this study. The exploratory data which attempted topredict the thermal process within the high-rise was acquired using pre-validatedcomputational fluid dynamics (CFD) and zone model simulations. In order to furtherinform the simulation results, data from two past small scale experiments (InformingCase Studies [ICS]) were analyzed. Interviews were carried out with fire fighters & fireengineers and findings discussed with that of ICS and literature to put the quantitativefindings within a qualitative context.The result of the study revealed some key findings; firstly, when a central core high-risemorphologies are dimensionally transformed, three morphological dynamics actuallytake place. The morphological dynamics are as follows: boundaries are reconfigured,regions at the sides of the central core are rearranged in relation to each other andorifices from the central core edges to the boundaries are redimensioned. Secondly, itwas also revealed that temperature development and peaks are higher in the regionadjacent to the ignition region when these regions relate to each other in a flushedmanner (rectilinear) than when there is a set back. Thirdly, further investigation wascarried out on simplified representation of the "flushed" and "setback" arrangementwhich revealed that for the adjacent regions, when the distance between the edge of thecore and boundaries exceeds 50% of the region width, the presence of a setback willresult in lower peak temperatures than when a setback is absent. From the study, regionrearrangement and orifice redimensioning, though they are effects of high-risemorphology changes, were also found to be active morphological drivers whenconsidering gas temperatures during high-rise fires. The effect of the boundaryreconfiguration was not studied but was identified as the third morphological driver andwas proposed for further studies. These simulation findings were corroborated byinterview findings that suggested similarities between observation of real fires andsimulation findings in terms of fire development. However, ignited dislodged fuel according to ICS and interview findings, tend to fall close to original fuel hence has nosignificant implication in terms of causing random remote ignition not accounted for insimulation.
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