Design of light gauge steel roofing systems subject to high wind forces

Light gauge steel roofing systems made of thin profiled roof sheeting and battens are used commonly in residential, industrial and commercial buildings. Their critical design load combination is that due to wind uplift forces that occur during high wind events such as tropical cyclones and thunderstorms. However, premature local failures at their screw connections have been a concern for many decades since cyclone Tracy that devastated Darwin in 1974. Extensive research that followed cyclone Tracy on the pull-through and pull-out failures of roof sheeting to batten connections has significantly improved the safety of roof sheeting. However, this has made the batten to rafter/truss connection the weakest, and recent wind damage investigations have shown the failures of these connections and the resulting loss of entire roof structures. Therefore an experimental research program using both small scale and full scale air-box tests is currently under way to investigate the pull-through failures of thin-walled steel battens under high wind uplift forces. Tests have demonstrated that occurrence of pull-through failures in the bottom flanges of steel batttens and the need to develop simple test and design methods as a function of many critical parameters such as steel batten geometry, thickness and grade, screw fastener sizes and other fastening details. This paper presents the details of local failures that occur in light fauge roofing systems, a review of the current design and test methods for steel battens and associated short comings, and the test results obtained to date on pull-through failures of battens from small scale and full scale tests. Finally, it proposes the use of suitable small scale test methods that can be used by both researchers and manufacturers of such screw-fastened light gauge steel batten systems.

Projecting the new world city: The city as spectacle in an urban light festival

As a precursor to the 2014 G20 Leaders’ Summit held in Brisbane, Australia, the Queensland Government sponsored a program of G20 Cultural Celebrations, designed to showcase the Summit’s host city. The cultural program’s signature event was the Colour Me Brisbane festival, a two-week ‘citywide interactive light and projection installations’ festival that was originally slated to run from 24 October to 9 November, but which was extended due to popular demand to conclude with the G20 Summit itself on 16 November. The Colour Me Brisbane festival comprised a series projection displays that promoted visions of the city’s past, present, and future at landmark sites and iconic buildings throughout the city’s central business district and thus transformed key buildings into forms of media architecture. In some instances the media architecture installations were interactive, allowing the public to control aspects of the projections through a computer interface situated in front of the building; however, the majority of the installations were not interactive in this sense. The festival was supported by a website that included information regarding the different visual and interactive displays and links to social media to support public discussion regarding the festival (Queensland Government 2014). Festival-goers were also encouraged to follow a walking-tour map of the projection sites that would take them on a 2.5 kilometre walk from Brisbane’s cultural precinct, through the city centre, concluding at parliament house. In this paper, we investigate the Colour Me Brisbane festival and the broader G20 Cultural Celebrations as a form of strategic placemaking—designed, on the one hand, to promote Brisbane as a safe, open, and accessible city in line with the City Council’s plan to position Brisbane as a ‘New World City’ (Brisbane City Council 2014). On the other hand, it was deployed to counteract growing local concerns and tensions over the disruptive and politicised nature of the G20 Summit by engaging the public with the city prior to the heightened security and mobility restrictions of the Summit weekend. Harnessing perspectives from media architecture (Brynskov et al. 2013), urban imaginaries (Cinar & Bender 2007), and social media analysis, we take a critical approach to analysing the government-sponsored projections, which literally projected the city onto itself, and public responses to them via the official, and heavily promoted, social media hashtags (#colourmebrisbane and #g20cultural). Our critical framework extends the concepts of urban phantasmagoria and urban imaginaries into the emerging field of media architecture to scrutinise its potential for increased political and civic engagement. Walter Benjamin’s concept of phantasmagoria (Cohen 1989; Duarte, Firmino, & Crestani 2014) provides an understanding of urban space as spectacular projection, implicated in commodity and techno-culture. The concept of urban imaginaries (Cinar & Bender 2007; Kelley 2013)—that is, the ways in which citizens’ experiences of urban environments are transformed into symbolic representations through the use of imagination—similarly provides a useful framing device in thinking about the Colour Me Brisbane projections and their relation to the construction of place. Employing these critical frames enables us to examine the ways in which the installations open up the potential for multiple urban imaginaries—in the sense that they encourage civic engagement via a tangible and imaginative experience of urban space—while, at the same time, supporting a particular vision and way of experiencing the city, promoting a commodified, sanctioned form of urban imaginary. This paper aims to dissect the urban imaginaries intrinsic to the Colour Me Brisbane projections and to examine how those imaginaries were strategically deployed as place-making schemes that choreograph reflections about and engagement with the city.

Energy based time equivalent approach to determine the fire resistance ratings of light gauge steel frame walls exposed to realistic design fire curves

Structural fire safety has become one of the key considerations in the design and maintenance of the built infrastructure. Conventionally the fire resistance rating of load bearing Light gauge Steel Frame (LSF) walls is determined based on the standard time-temperature curve given in ISO 834. Recent research has shown that the true fire resistance of building elements exposed to building fires can be less than their fire resistance ratings determined based on standard fire tests. It is questionable whether the standard time-temperature curve truly represents the fuel loads in modern buildings. Therefore an equivalent fire severity approach has been used in the past to obtain fire resistance rating. This is based on the performance of a structural member exposed to a realistic design fire curve in comparison to that of standard fire time-temperature curve. This paper presents the details of research undertaken to develop an energy based time equivalent approach to obtain the fire resistance ratings of LSF walls exposed to realistic design fire curves with respect to standard fire exposure. This approach relates to the amount of energy transferred to the member. The proposed method was used to predict the fire resistance ratings of single and double layer plasterboard lined and externally insulated LSF walls. The predicted fire ratings were compared with the results from finite element analyses and fire design rules for three different wall configurations exposed to both rapid and prolonged fires. The comparison shows that the proposed energy method can be used to obtain the fire resistance ratings of LSF walls in the case of prolonged fires.

Integrating LED lighting design strategies with side daylighting systems to improve interior lighting design of office buildings

A high contrast ratio between windows and surrounding walls may lead to office workers visual discomfort that could negatively affect their satisfaction and productivity. Consequently, occupants may try to adapt their working environment by closing blinds and/ or turning on the lights to enhance indoor visual comfort, which can reduce predicted energy savings. The hypothesis of this study is that reducing luminance contrast ratio on the window wall will improve window appearance which potentially will reduce visual discomfort and decrease workers interventions. Thus, this PhD research proposes a simple strategy to diminish the luminance contrast on the window wall by increasing the luminance of the areas surrounding the windows using supplementary light emitting diode (LED) systems. To test the hypothesis, this investigation will involve three experiments in different office layouts with various window types and orientations in Brisbane, Australia. It will assess user preferences for different luminance patterns in windowed offices featuring flexible, lowpower LED lighting installations that allows multiple lighting design options on the window wall. Detailed luminance and illuminance measures will be used to match quantitative lighting design assessment to user preferences.

Fire resistance of light gauge steel frame wall systems lined with gypsum plasterboards

Light gauge steel frame (LSF) wall systems are increasingly used in residential and commercial buildings as load bearing and non-load bearing elements. Conventionally, the fire resistance ratings of such building elements are determined using approximate prescriptive methods based on limited standard fire tests. However, recent studies have shown that in some instances real building fire time-temperature curves could be more severe than the standard fire curve, in terms of maximum temperature and rate of temperature rise. This has caused problems for safe evacuation and rescue activities, and in some instances has also lead to the collapse of buildings earlier than the prescribed fire resistance. Therefore a detailed research study into the performance of LSF wall systems under both standard fire and realistic fire conditions was undertaken using full scale fire tests to understand the fire performance of different LSF wall configurations. Both load bearing and non-load bearing full scale fire tests were performed on LSF walls configurations which included single layer, double layer, externally insulated wall panels made up of different steel sections and thicknesses of gypsum plasterboards. The non-load bearing fire test results were utilized to understand the factors affecting the fire resistance of LSF walls, while loading bearing fire test results led to development of simplified methods to predict the fire resistance ratings of load bearing LSF walls exposed to both standard and realistic design fires. This paper presents the results of full scale experimental study and highlights the effects of standard and realistic fire conditions on fire performance of LSF walls.

Implication of global warming on air-conditioned office buildings in Australia

With the accelerated trend of global warming, the thermal behavior of existing buildings, which were typically designed based on current weather data, may not be able to cope with the future climate. This paper quantifies, through computer simulations, the increased cooling loads imposed by potential global warming and probable indoor temperature increases due to possible undersized air-conditioning system. It is found from the sample office building examined that the existing buildings would generally be able to adapt to the increasing warmth of 2030 year Low and High scenarios projections and 2070 year Low scenario projection. However, for the 2070 year High scenario, the study indicates that the existing office buildings, in all capital cities except for Hobart, will suffer from overheating problems. When the annual average temperature increase exceeds 2°C, the risk of current office buildings subjected to overheating will be significantly increased. For existing buildings which are designed with current climate condition, it is shown that there is a nearly linear correlation between the increase of average external air temperature and the increase of building cooling load. For the new buildings, in which the possible global warming has been taken into account in the design, a 28-59% increase of cooling capacity under 2070 High scenario would be required to improve the building thermal comfort level to an acceptable standard.