Design of a portable bushfire attenuation fence

Fell, Bradley (2016) Design of a portable bushfire attenuation fence. [USQ Project]

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Abstract

Bushfires are natural disasters that occur frequently in Australia, and are associated with substantial economic and human costs. Currently, methods of combating bushfire
propagation rely predominantly on containment through the use of firebreaks; large open areas devoid of fuel to sustain the fire. However, ignited embers (firebrands) are often carried via wind across these spaces, leading to the fire spreading to the other side. Additionally, accumulation of these firebrands around buildings are responsible for a vast majority of homes destroyed in a bushfire event.

In this project, a novel new approach to preventing firebrand transmission is investigated. Fine aperture wire mesh screen barriers have been demonstrated in laboratory experiments to reduce the transmission of firebrand particles and prevent the subsequent accumulation
on and ignition of flammable fuel beds. Therefore, the concept of constructing a large, portable fence comprising of this mesh material is investigated; with determination of
required parameters and specifications carried out before a prototype computational design was developed and validated through the use of Finite Element Analysis.

In addition to the development of a preliminary design, an assessment criterion was developed in which the performance of a bushfire attenuation fence design could be evaluated, leading to the ability to qualitatively rank and refine designs based upon factors such as weight per unit length; cost per unit length and assembly time per unit length.

Investigation into the conditions associated with both close proximity to bushfires and the mechanics of their propagation lead to the selection of a maximum design wind speed of 28 m/s (100.8 km/h), a peak design temperature of 500oC and a required fence height of 10 metres.

Feasibility analysis on various assembly and grounding methods lead to the selection of a combination of temporary ground screw anchors and guy wires as method of securing the
fence, with the maximum fence span with this configuration being 10 metres.

Detailed design of individual fence components was then carried out, with the final design subjected to FEA validation under the imposed loads and conditions. The results of the final design specified was then evaluated against the assessment criteria developed, with the
estimated results being 2.64 tonnes per 100 metres and assembly time estimates of between 25.5 to 38.7 metres per hour depending upon the assumptions used.


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Item Type: USQ Project
Item Status: Live Archive
Additional Information: Bachelor of Engineering (Honours) Major Mechanical Engineering project.
Faculty / Department / School: Current - Faculty of Health, Engineering and Sciences - School of Mechanical and Electrical Engineering
Supervisors: Sharifian, Ahmad
Date Deposited: 20 Jul 2017 02:14
Last Modified: 07 Aug 2018 23:55
Uncontrolled Keywords: firebrand transmission; finite element analysis; portable bushfire attenuation
Fields of Research : 09 Engineering > 0913 Mechanical Engineering > 091399 Mechanical Engineering not elsewhere classified
URI: http://eprints.usq.edu.au/id/eprint/31403

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