ABSTRACT
To model the spread of fire through informal settlements (also known as slums, favelas, shantytowns, etc.) it is important to be able to approximate the time at which structural collapse of the dwellings (sometimes referred to as “shacks”) occur. Fire spread models can be an important tool for analyzing how to improve the fire safety of settlements through layout reconfiguration, or for analyzing the influence of different construction types. This paper provides input to fire spread models by developing a methodology for determining the time to the structural collapse of informal dwellings based upon experimental data and methods in the literature. The paper compares theoretical collapse times (based on the effective cross-section method) to experimental collapse times to evaluate whether structural fire engineering principles can be applied to informal structures, which are areas where there is untreated timber, eccentric members, out-of-straight elements, etc. Data from four full-scale experiments consisting of 8 dwellings has been utilized, and this data consists of both timber clad and corrugated steel clad dwellings. The timber clad dwellings experience a sway collapse (i.e. as a result of the cladding burning away) whilst the steel clad dwellings experience roof collapse as a result of the simply supported ceiling beam failing in bending. All timber clad dwellings collapsed approximately 5 minutes after flashover and the steel dwellings collapse approximately 6–8 minutes after flashover. The effective cross section method indicates that for both the timber clad and steel clad dwellings the theoretical time to collapse falls within the range of the experimental collapse times. Even though there are significant uncertainties inherent in analyzing informal settlements this work provides novel insight with regards to how structural fire engineering principles can be applied within sub-models of systems analyzing fire risk and spread, such that the safety of the 1 billion people living in informal settlements can be improved.
