Abstract
While fire-related injuries and deaths decreased in the global north over the past few years, they have increased in the global south. With more than one billion people residing in informal settlements (sometimes known as slums, ghettos or shantytowns), it is necessary that greater effort be placed on addressing and developing means for improving fire safety in these areas. As a result of advances made in computer technologies, emerging performance-based regulations and an increase in building complexity in the global north, the use of computer models simulating enclosure fires have increased dramatically. In this work an experimental investigation is presented for (a) a full-scale corrugated steel sheeting clad informal dwelling experiment and (b) a full-scale timber clad informal dwelling experiment. The experimental results are then compared to numerical models consisting of both simple two-zone (OZone) and computational fluid dynamic models. Currently, there is negligible literature available on Fire Dynamic Simulator (FDS) modelling of informal settlement dwellings (sometimes known as shacks or shanties) fires. This paper evaluates the plausibility of using FDS v6.7 and zonal models to predict certain fire parameters (i.e. ceiling temperatures, heat fluxes, etc.) for Informal Settlement Dwellings (ISDs) and to study the plausibility of using FDS to estimate the probability of fire spread. In this paper an introduction to ISDs is given with details pertaining to construction materials and considerations needed for numerical modelling of informal dwellings (i.e. thin permeable boundaries or combustible boundaries). Models are based upon (a) a prescribed heat release rate per unit area in FDS using data obtained from a Fire Propagation Apparatus test, and (b) an empirical two-zone model using OZone. The FDS validation guide was used to quantify the model uncertainties in order to give a critical separation distance at which fire spread between dwellings will not occur. It was found that at 3 m spacing between ISDs there is a 6% chance (based on the model uncertainties) that fire spread can occur. This is an important finding that highlights the danger associated with these closely spaced dwellings and the hope is that it can guide local government and Non-Governmental Organizations in future decision making. Three meters spacing between dwellings, however, may not be possible due to the socio-cultural-political-economic issues associated with informal settlements. This is one of the first papers to demonstrate FDS models against full-scale ISD experiments.
Highlights
In the world, there are currently an estimated 300,000 fire-related deaths per year with more than 95% of those deaths occurring in middle to lower-income groups [1]
Previous work has focused on results from preliminary single dwellings experiments [5], results from multi-dwelling experiments considering inter-dwelling spread [19], the development of a simplified Fire Dynamic Simulator (FDS) model to describe the aforementioned multi-dwelling experiment [20], analysis of large-scale spread in a real fire disaster that affected over 2000 homes [11], and the appraisal of fire safety interventions to be used in such settlements [21]
The authors conducted a cell sensitivity study in [20], where the model consisted of multiple Informal settlement dwellings (ISDs) with the same cladding materials and cardboard lining and it was found that a cell size of 0.1 m was sufficient to capture the ceiling temperatures, heat fluxes emitted from the dwelling and the cardboard behaviour
Summary
There are currently an estimated 300,000 fire-related deaths per year with more than 95% of those deaths occurring in middle to lower-income groups [1]. The number of people that reside in informal settlements is expected to increase from one billion worldwide to 1.2 billion people in Africa alone by 2050 [6] It is of concern, to see how little work is being done to improve the fire safety in these communities. In 2017, approximately 2200 homes were razed, affecting approximately 9700 people in the Imizamo Yethu informal settlement in Cape Town [11]. These fires do not just cause loss of life in these communities, but significant morbidity with over 10 M disability adjusted life years lost each year due to fire, and loss of belongings (such as official documents, educational material) and livelihoods. Previous work has focused on results from preliminary single dwellings experiments [5], results from multi-dwelling experiments considering inter-dwelling spread [19], the development of a simplified FDS model to describe the aforementioned multi-dwelling experiment [20], analysis of large-scale spread in a real fire disaster that affected over 2000 homes [11], and the appraisal of fire safety interventions to be used in such settlements [21]
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