BEng/MEng – 2017 fire theses

The Bachelor (Honours) and Master of Engineering, 5-year full-time program (80 units) combines Civil Engineering with additional courses in Fire Safety Engineering. To obtain their degrees, students are required to undertake a one-year long Fire Research Project (FIRE7500). Photos below were taken during an oral seminar presentation held at the end of the second semester. Also, a brief description of the 2017 fire research theses is also shown below.

 

Proof-Of-Concept For A Fire Safe Timber-FRP Composite Load-Bearing System

by Harrison Wall

With the increased interest and use of large engineered timber members within major structures (ie. tall timber buildings), comes the increase need for understanding the fire performance to ensure these structures can be used with confidence. Aim at improving the structural fire performance of glue laminated timber, it is proposed that the member be reinforced with carbon Fibre Reinforced Polymer (FRP) between the two bottom lamellas. The inclusion of the carbon fibre is expected to increase stiffness and capacity of the system; however, it is hypothesised that the carbon will maintain structural capacity after the loss of the adhesive layer, therefore increasing the structural fire performance of the member.

To investigate the impact of the FRP, a numerical and experimental investigation was undertaken. The numerical modelling assessed the performance from first principle approach and utilised a section analysis. From the numerical modelling, it was concluded that the inclusion of the FRP resulted in a significant increase in section capacity at both ambient and fire simulated conditions. The experiment investigation conducted three series of structural four-point bending tests, one at ambient and two at fire loading conditions. The first test series assessed the ambient performance the timber which found that it achieved a bending strength of 62.8 MPa.

The results from the experimental investigation evidenced that a glulam-FRP composite will achieve maintain structural capacity for a longer duration, achieved a large failure deflection, and will fail in a pseudo-ductile manner in lieu of the brittle failure that is characteristic of timber. While pseudo-ductile failure has been observed within glulam-FRP composite within ambient studies, until now it has not been observed during fire loading conditions. Furthermore, the results suggest that carbon fibre was able to maintain capacity after the loss of the adhesive, therefore supporting the research hypothesis. Overall the outcomes of this investigation suggest that the inclusion of carbon fibre within glulam lamellas can improve the structural fire performance.

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Design Fires for Large Artificial Christmas Trees

by Luke Thompson

Christmas trees are common seasonal decorations that are popular to install in homes, offices, commercial areas and public spaces. Although Christmas trees have this seasonal usage around the Christmas period, 20% of residential Christmas tree fires were found to occur from February to November. Currently, research into the fire safety hazard of Christmas trees has focused on the ignition of natural trees. However, design fires for artificial Christmas trees have received little attention.

This work investigated the formulation of a design fire for commercial-scale artificial Christmas trees. The burning behaviour of the artificial Christmas trees is dependent on the material and geometry/scaling effects. This research explored scaling of results towards the development of design fire that may be used to assess the risk posed by artificial Christmas trees. Bench-scale experiments were used to investigate the fundamental burning behaviour of the material tested. Medium and large-scale tests of 1 m, 1.5 m, and 3.75 m were undertaken to assess the full system behaviour.

The experiments were used to obtain fundamental fire parameters for quantities such as the effective heat of combustion, mass loss rate per unit area, flame spread rate, among others. Results in combination with data analysis were used to develop and validate empirical correlations describing the growth of the fire and its peak heat release rate. Tree height was observed to be the most important geometrical variable controlling the growth and size of the fire in the proposed correlations.

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Fire Exposure of Façades in Cross-Laminated Timber Buildings

by Teagan MacDonald

Engineered wood products such as Cross-Laminated Timber (CLT), which consists of layers glued perpendicularly to each other, are gaining attention as they are advantageous for this type of construction due to their strength to weight ratio, aesthetics, sustainability, and cost to produce and construct with.

A major cause of flame spread within mid- and high-rise construction has been attributed to vertical flame spread along the façade. Vertical flame spread is most commonly observed when flashover occurs in a ventilation controlled compartment, whereby the temperatures and heat fluxes are high enough such that the combustible materials within the compartment pyrolyse resulting in large quantities of flammable gases. Within ventilation-controlled compartment fires, the openings are small such that the oxygen in the compartment is limited the resultant pyrolysis gases will flow out of any opening resulting in external combustion and potential vertical flame spread. Exposed CLT within compartments will likely result in an increase in pyrolysis gases thus additional threat to the façade.

The intent of this study is to develop a design methodology in which the threat to the façade as a result of a CLT-lined compartment can be quantified. In order to investigate this, a series of medium-scale compartment tests were carried out. Using a compartment box with a mock-façade fixed at the opening of the façade, the incident radiant heat flux to the façade was measured as a result of varied areas of exposed CLT within the compartment. Within each experiment, the configuration of exposed CLT walls within the compartment was varied (including a series of experiments in which no CLT was exposed, i.e. baseline), which allowed for characterisation of dependency of the heat flux to the façade. Using the ideal fire plume and the experimental results an empirical relationship was developed to correlate the incident radiant heat flux to the façade with the area of exposed CLT within the compartment.

Given the experiments were carried out using a medium-scale compartment, a scaling analysis was pursued, such that the relationship could be validated and applied to full-scale scenarios. This was carried out using the Law Model and fluid dynamics between the results of a Large-Scale experiment previously carried out.

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Behaviour of intumescent coatings under a range of fire conditions

by Jupiter Segall-Brown

To investigate the influence of the heating conditions on the performance and behaviour of intumescent coatings, a series of tests were conducted utilising a Heat-Transfer Rate Inducing System (H-TRIS). The fire test method permitted a wide range of heating conditions to be tested. The samples used for testing were a series of steel plates with a commercially available thin intumescent coating applied.

The results of testing utilising different heating conditions was compared against a simple heat transfer model, calibrated to represent the sample before the coating had undergone the intumescent process. The results obtained from the experiments conducted were visual observations, in addition to the experimental temperature at the back face of the intumescent sample. Modelling was conducted to approximate the temperatures of the intumescent coating and net energy heat fluxes.

An analysis of the results indicated the intumescent coating behaviour, in relation to the heating curve, was highly dependent on the chemical properties of the coating and underwent three main events during heating: Pre-Activation, Local Activation, and Global Activation. The chemical reaction was found to commence at Pre-Activation, with the intumescing of the sample occurring at the Global Activation stage. For the coating tested, Pre-Activation was found to occur at approximately between 160 and 180 °C, based upon modelled temperatures and the results of the thermal expansion coefficient and thermogravimetric analysis of the intumescent. The effectiveness of the paint was found to depend on the energy absorbed between Pre- Activation and Global Activation, with the heating curve before Pre-Activation having no discernible impact on the effectiveness of the coating.

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Fire Performance of ACP Panels

by Joshua Ogilvie

This work describes a methodology to characterise the fire performance of Aluminium Composite Panel (ACP) façade systems. This methodology is based on material characterisation and both qualitative and quantitative assessment of fire performance of combustible cladding products. The current testing methodology involves a series of pass/fail criteria relating to the combustible nature of building materials, components and structures. It is considered that a more performance-based methodology should be developed to better understand the how these products behave during a fire.

In order to better understand and characterise the fire performance of ACP products, a fire testing methodology was developed. A series of small-scale experimental programmes were carried out, in order to initially identify the material chemistry and then start to develop more of a holistic understanding by focusing on aspects such as the thermochemistry, ignitability and flame spread.

Results from this work provide a preliminary understanding of the behavioural characteristics and performance of ACP product during a fire. Additional work is required to expand on the fire testing methodology, and also demonstrate key fire performance outcomes using series of large-scale experiments.

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Mechanical Properties of Bamboo at Elevated Temperatures

by Joshua Madden

With the increasing awareness of climate change, governments, industry, and academia around the world are constantly striving for sustainable alternative renewable materials with lower environmental impacts. Laminated bamboo is an alternative building construction material that possesses remarkable overall characteristics. It has a high growth rate (3 to 5 years) and is prominent throughout the world. Structural timber has a growth rate of up to 20 years and combines with the effects of deforestation, is no longer seen as a long-term alternative. Modern laminated bamboo products can exceed the mechanical performance of laminated timber products.

Despite the above-mentioned advantages, the reduction in mechanical properties at elevated temperature of bamboo and the structural performance of bamboo structures during or after fire is not understood. These limits the use of bamboo to applications where fire safety considerations are not relevant; i.e. low – rise and relatively simple buildings. Structural performance during and after fire enables engineers to design key aspects of the fire safety strategy.

Results presented herein allow understanding the reduction in the compressive strength and elastic modulus of laminated bamboo at elevated temperatures. A shift in the failure mechanisms was observed during the tests; from crushing to global buckling of test samples. Additionally, test of scaled bamboo columns enabled a verification study where reductions of mechanical were included into a model of the tested columns. Results herein set the basis for using laminated bamboo in applications were appropriate structural performance is required during and after a fire

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An Analysis of the Energy Distribution within Open-Plan Compartment Fire

by Nicholas White

A study conducted during 2016 regarding the large-scale experiments performed at BRE (Watford) found that approximately 80% of the energy losses within an open plan compartment fire are as a result of the losses to the openings. To date, the openings are the least understood aspect of a Regime II compartment fire. Past work into understanding the energy lost through openings has contained large scatter, and many simplifications.

This work aims at further understanding into the unknowns, and apply a variety of techniques, coupled with a thorough understanding of the other components of a compartment fire to reduce the uncertainty and error of such calculations.

It was found that, resorting back to first principles, allowed for the error in the energy loss calculations for the openings to be reduced. The primary source of uncertainty was determining the height of the smoke layer, as only a minor amount of inaccuracy was required to distort the results completely.

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