Methods for the illumination of multilevel buildings with vertical light pipes

This paper examines the feasibility of using vertical light pipes to naturally illuminate the central core of a multilevel building not reached by window light. The challenges addressed were finding a method to extract and distribute equal amounts of light at each level and designing collectors to improve the effectiveness of vertical light pipes in delivering low elevation sunlight to the interior. Extraction was achieved by inserting partially reflecting cones within transparent sections of the pipes at each floor level. Theory was formulated to estimate the partial reflectance necessary to provide equal light extraction at each level. Designs for daylight collectors formed from laser cut panels tilted above the light pipe were developed and the benefits and limitations of static collectors as opposed to collectors that follow the sun azimuth investigated. Performance was assessed with both basic and detailed mathematical simulation and by observations made with a five level model building under clear sky conditions.

Improving daylighting performance of mirrored light pipes

This paper assesses and compares the performances of two daylight collection strategies, one passive and one active, for large-scale mirrored light pipes (MLP) illuminating deep plan buildings. Both strategies use laser cut panels (LCP) as the main component of the collection system. The passive system comprises LCPs in pyramid form, whereas the active system uses a tiled LCP on a simple rotation mechanism that rotates 360° in 24 hours. Performance is assessed using scale model testing under sunny sky conditions and mathematical modelling. Results show average illuminance levels for the pyramid LCP ranging from 50 to 250 lux and 150 to 200 lux for the rotating LCPs. Both systems improve the performance of a MLP. The pyramid LCP increases the performance of a MLP by 2.5 times and the rotating LCP by 5 times, when compared to an open pipe particularly for low sun elevation angles.

Full scale fire tests of a new light gauge steel floor-ceiling system

Cold-formed steel members can be assembled in various combinations to provide cost-efficient and safe light gauge floor systems for buildings. Such Light gauge Steel Framing (LSF) systems are widely accepted in industrial and commercial building construction. An example application is in floor-ceiling systems. Light gauge steel floor-ceiling systems must be designed to serve as fire compartment boundaries and provide adequate fire resistance. Fire-rated floor-ceiling assemblies formed with new materials and construction methodologies have been increasingly used in buildings. However, limited research has been undertaken in the past and hence a thorough understanding of their fire resistance behaviour is not available. Recently a new composite floor-ceiling system has been developed to provide higher fire rating under standard fire conditions. But its increased fire rating could not be determined using the currently available design methods. Therefore a research project was carried out to investigate its structural and fire resistance behaviour under standard fire conditions. In this research project full scale experimental tests of the new LSF floor system based on a composite ceiling unit were undertaken using a gas furnace at the Queensland University of Technology. Both the conventional and the new steel floor-ceiling systems were tested under structural and fire loads. Full scale fire tests provided a good understanding of the fire behaviour of the LSF floor-ceiling systems and confirmed the superior performance of the new composite system. This paper presents the details of this research into the structural and fire behaviour of light gauge steel floor systems protected by the new composite panel, and the results.

Improvements to the fire performance of light gauge steel floor systems

Light gauge steel frame (LSF) structures are increasingly used in commercial and residential buildings because of their non-combustibility, dimensional stability and ease of installation. A common application is in floor-ceiling systems. The LSF floor-ceiling systems must be designed to serve as fire compartment boundaries and provide adequate fire resistance. Fire-rated floor-ceiling assemblies have been increasingly used in buildings. However, limited research has been undertaken in the past and hence a thorough understanding of their fire resistance behaviour is not available. Recently a new composite floor-ceiling system has been developed to provide higher fire rating. But its increased fire rating could not be determined using the currently available design methods. Therefore a research project was conducted to investigate its structural and fire resistance behaviour under standard fire conditions. This paper presents the results of full scale experimental investigations into the structural and fire behaviour of the new LSF floor system protected by the composite ceiling unit. Both the conventional and the new floor systems were tested under structural and fire loads. It demonstrates the improvements provided by the new composite panel system in comparison to conventional floor systems. Numerical studies were also undertaken using the finite element program ABAQUS. Measured temperature profiles of floors were used in the numerical analyses and their results were compared with fire test results. Tests and numerical studies provided a good understanding of the fire behaviour of the LSF floor-ceiling systems and confirmed the superior performance of the new composite system.

The design and testing of a daylighting device : optimising the energy and optical performance of Australian commercial buildings

The effective daylighting of multistorey commercial building interiors poses an interesting problem for designers in Australia’s tropical and subtropical context. Given that a building exterior receives adequate sun and skylight as dictated by location-specific factors such as weather, siting and external obstructions; then the availability of daylight throughout its interior is dependant on certain building characteristics: the distance from a window façade (room depth), ceiling or window head height, window size and the visible transmittance of daylighting apertures. The daylighting of general stock, multistorey commercial buildings is made difficult by their design limitations with respect to some of these characteristics. The admission of daylight to these interiors is usually exclusively by vertical windows. Using conventional glazing, such windows can only admit sun and skylight to a depth of approximately 2 times the window height. This penetration depth is typically much less than the depth of the office interiors, so that core areas of these buildings receive little or no daylight. This issue is particularly relevant where deep, open plan office layouts prevail. The resulting interior daylight pattern is a relatively narrow perimeter zone bathed in (sometimes too intense) light, contrasted with a poorly daylit core zone. The broad luminance range this may present to a building occupant’s visual field can be a source of discomfort glare. Furthermore, the need in most tropical and subtropical regions to restrict solar heat gains to building interiors for much of the year has resulted in the widespread use of heavily tinted or reflective glazing on commercial building façades. This strategy reduces the amount of solar radiation admitted to the interior, thereby decreasing daylight levels proportionately throughout. However this technique does little to improve the way light is distributed throughout the office space. Where clear skies dominate weather conditions, at different times of day or year direct sunlight may pass unobstructed through vertical windows causing disability or discomfort glare for building occupants and as such, its admission to an interior must be appropriately controlled. Any daylighting system to be applied to multistorey commercial buildings must consider these design obstacles, and attempt to improve the distribution of daylight throughout these deep, sidelit office spaces without causing glare conditions. The research described in this thesis delineates first the design optimisation and then the actual prototyping and manufacture process of a daylighting device to be applied to such multistorey buildings in tropical and subtropical environments.

Perceptions of daylight quality delivered by light transport systems

Light Transport Systems (LTS) (e.g lightpipes, fibre optics) can illuminate core areas within buildings with great potential for energy savings. However, they do not provide a clear connection to the outside like windows do, and their effects on people’s physiological and psychological health are not well understood. Furthermore, how people perceive LTS affects users’ acceptance of the device and its performance. The purpose of this research is to understand how occupants perceive and experience spaces illuminated by LTS. Two case studies of commercial buildings with LTS, located in Brisbane, Australia are assessed by qualitative (focus group interviews) and quantitative (measurement of daylight illuminances and luminance) methods. The data from interviews with occupants provide useful insight into the aspects of LTS design that are most relevant to positive perception of the luminous environment. Luminance measurements of the occupied spaces support the perception of the LTS reported by occupants: designs that create high contrast luminous environments are more likely to be perceived negatively.

Numerical modelling of light gauge cold-formed steel compression members subjected to distortional buckling at elevated temperatures

Fire safety design of building structures has received greater attention in recent times due to continuing loss of properties and lives during fires. However, fire performance of light gauge cold-formed steel structures is not well understood despite its increased usage in buildings. Cold-formed steel compression members are susceptible to various buckling modes such as local and distortional buckling and their ultimate strength behaviour is governed by these buckling modes. Therefore a research project based on experimental and numerical studies was undertaken to investigate the distortional buckling behaviour of light gauge cold-formed steel compression members under simulated fire conditions. Lipped channel sections with and without additional lips were selected with three thicknesses of 0.6, 0.8, and 0.95 mm and both low and high strength steels (G250 and G550 steels). More than 150 compression tests were undertaken first at ambient and elevated temperatures. Finite element models of the tested compression members were then developed by including the degradation of mechanical properties with increasing temperatures. Comparison of finite element analysis and experimental results showed that the developed finite element models were capable of simulating the distortional buckling and strength behaviour at ambient and elevated temperatures up to 800 °C. The validated model was used to determine the effects of mechanical properties, geometric imperfections and residual stresses on the distortional buckling behaviour and strength of cold-formed steel columns. This paper presents the details of the numerical study and the results. It demonstrated the importance of using accurate mechanical properties at elevated temperatures in order to obtain reliable strength characteristics of cold-formed steel columns under fire conditions.

The impacts of power outages on the residents of contemporary multistorey apartment buildings in subtropical environments

With significant population growth experienced in South East Queensland over the past two decades and a high rate of growth expected to continue in coming decades, the Queensland Government is promoting urban consolidation planning policies to manage growth sustainably. Multi-residential buildings will play an important role in facilitating the increased densities which urban consolidation policies imply. However, a major flood event in January 2011 has brought to light the vulnerability of certain types of multi-residential typologies to power outages. The crisis conditions exposed how contemporary building design and construction practices, coupled with regulatory and planning issues, appear to have compromised the resilience and habitability of multi-storey residential buildings. In the greater urban area of Brisbane, Queensland, the debilitating dependence that certain types of apartment buildings have on mains electricity was highlighted by residents’ experiences of the Brisbane River flood disaster, before, during and after the event. This research examined high density residential buildings in West End, Brisbane, an inner city suburb which was severely affected by the flood and is earmarked for significant urban densification under the Brisbane City Plan. Medium-to-high-density residential buildings in the suburb were mapped in flooded and non-flooded locations and a database containing information about the buildings was created. Parameters included date of construction, number of storeys, systems of access and circulation, and potential for access to natural light and ventilation for habitable areas. A series of semi-structured interviews were conducted with residents involved in the owners’ management committees of several buildings to verify information the mapping could not provide. The interviews identified a number of critical systems failures due to power outage which had a significant impact on residents’ wellbeing, comfort and safety. Building services such as lifts, running water, fire alarms, security systems and air-conditioning ceased to operate when power was disconnected to neighbourhoods and buildings in anticipation of rising flood waters. Lack of access to buildings and dwellings, lack of safety, lack of building security, and lack of thermal comfort affected many residents whether or not their buildings were actually subjected to inundation, with some buildings rendered uninhabitable for a prolonged period. The extent of the impact on residents was dramatically influenced by the scale and type of building inhabited, with those dwelling in buildings under a 25m height limit, with a single lift, found to be most affected. The energy-dependency and strong trend of increasing power demands of high-rise buildings is well-documented. Extended electricity outages such as the one brought about by the 2011 flood in Queensland are likely to happen more frequently than the 50-year average of the flood event itself. Electricity blackouts can result from a number of man-made or natural causes, including shortages caused by demand exceeding supply. This paper highlights the vulnerability of energy-dependent buildings to power outages and investigates options for energy security for occupants of multi-storey buildings and makes recommendations to increase resilience and general liveability in multi-residential buildings in the subtropics through design modifications.

An assessment tool for selection of appropriate daylighting solutions for buildings in tropical and subtropical regions : Validation using radiance simulation

A new decision-making tool that will assist designers in the selection of appropriate daylighting solutions for buildings in tropical locations has been previously proposed by the authors. Through an evaluation matrix that prioritizes the parameters that best respond to the needs of tropical climates (e.g. reducing solar gain and protection from glare) the tool determines the most appropriate devices for specific climate and building inputs. The tool is effective in demonstrating the broad benefits and limitations of the different daylight strategies for buildings in the tropics. However for thorough analysis and calibration of the tool, validation is necessary. This paper presents a first step in the validation process. RADIANCE simulations were conducted to compare simulation performance with the performance predicted by the tool. To this end, an office building case study in subtropical Brisbane, Australia, and five different daylighting devices including openings, light guiding systems and light transport systems were simulated. Illuminance, light uniformity, daylight penetration and glare analysis were assessed for each device. The results indicate the tool can appropriately rank and recommend daylighting strategies based on specific building inputs for tropical and subtropical regions, making it a useful resource for designers.

Fire safety of buildings based on realistic fire time-temperature curves

In recent times, fire has become a major disaster in buildings due to the increase in fire loads, as a result of modern furniture and light weight construction. This has caused problems for safe evacuation and rescue activities, and in some instances lead to the collapse of buildings (Lewis, 2008 and Nyman, 2002). Recent research has shown that the actual fire resistance of building elements exposed to building fires can be less than their specified fire resistance rating (Lennon and Moore, 2003, Jones, 2002, Nyman, 2002 and Abecassis-Empis et al. 2008). Conventionally the fire rating of building elements is determined using fire tests based on the standard fire time-temperature curve given in ISO 834. This ISO 834 curve was developed in the early 1900s, where wood was the basic fuel source. In reality, modern buildings make use of thermoplastic materials, synthetic foams and fabrics. These materials are high in calorific values and increase both the speed of fire growth and heat release rate, thus increasing the fire severity beyond that of the standard fire curve. Hence it suggests the need to use realistic fire time-temperature curves in tests. Real building fire temperature profiles depend on the fuel load representing the combustible building contents, ventilation openings and thermal properties of wall lining materials. Fuel load is selected based on a review and suitable realistic fire time-temperature curves were developed. Fire tests were then performed for plasterboard lined light gauge steel framed walls for the developed realistic fire curves. This paper presents the details of the development of suitable realistic building fire curves, and the fire tests using them. It describes the fire performance of tested walls in comparison to the standard fire tests and highlights the differences between them. This research has shown the need to use realistic fire exposures in assessing the fire resistance rating of building elements.

Developing sustainable ‘liveable’ buildings, cities and communities for a sub-tropical context : residents’ perspectives

A key challenge for the 21st Century is to make our cities more liveable and foster economically sustainable, environmentally responsible, and socially inclusive communities. Design thinking, particularly a human-centred approach, offers a way to tackle this challenge. Findings from two recent Australian research projects highlight how facilitating sustainable, liveable communities in a humid sub-tropical environment requires an in-depth understanding of people’s perspectives, experiences and practices. Project 1 (‘Research House’) documents the reflections of a family who lived in a ‘test’ sustainable house for two years, outlining their experience and evaluations of universal design and sustainable technologies. The study family was very impressed with the natural lighting, natural ventilation, spaciousness and ease of access, which contributed significantly to their comfort and the liveability of their home. Project 2 (‘Inner-Urban High Density Living’) explored Brisbane residents’ opinions about high-density living, through a survey (n=636), interviews (n=24), site observations (over 300 hours) and environmental monitoring, assessing opinions on the liveability of their individual dwelling, the multi-unit host building and the surrounding neighbourhood. Nine areas, categorised into three general domains, were identified as essential for enhancing high density liveability. In terms of the dwelling, thermal comfort/ventilation, natural light, noise mitigation were important; shared space, good neighbour protocols, and support for environmentally sustainable behaviour were desired in the building/complex; and accessible/sustainable transport, amenities and services, sense of community were considered important in the surrounding neighbourhood. Combined, these findings emphasise the importance and complexity associated with designing liveable building, cities and communities, illustrating how adopting a design thinking, human-centred approach will help create sustainable communities that will meet the needs of current and future generations.

Numerical modelling of load bearing light gauge steel frame wall systems exposed to realistic design fires

Fire safety has become an important part in structural design due to the ever increasing loss of properties and lives during fires. Conventionally the fire rating of load bearing wall systems made of Light gauge Steel Frames (LSF) is determined using fire tests based on the standard time-temperature curve in ISO834 [1]. However, modern commercial and residential buildings make use of thermoplastic materials, which mean considerably high fuel loads. Hence a detailed fire research study into the fire performance of LSF walls was undertaken using realistic design fire curves developed based on Eurocode parametric [2] and Barnett’s BFD [3] curves using both full scale fire tests and numerical studies. It included LSF walls without cavity insulation, and the recently developed externally insulated composite panel system. This paper presents the details of finite element models developed to simulate the full scale fire tests of LSF wall panels under realistic design fires. Finite element models of LSF walls exposed to realistic design fires were developed, and analysed under both transient and steady state fire conditions using the measured stud time-temperature curves. Transient state analyses were performed to simulate fire test conditions while steady state analyses were performed to obtain the load ratio versus time and failure temperature curves of LSF walls. Details of the developed finite element models and the results including the axial deformation and lateral deflection versus time curves, and the stud failure modes and times are presented in this paper. Comparison with fire test results demonstrate the ability of developed finite element models to predict the performance and fire resistance ratings of LSF walls under realistic design fires.