A history of fire
brackets; with each floor plate subdivided into two compartments to limit the number of bracing elements that could reduce stability in the event of a compartment fire. This work on external structure in fire conditions went on to form Building Standards, in the UK, America and Europe.
THE EIGHTIES AND IMPACT OF ARCHITECTURAL DESIGN During the eighties, fire safety engineering continued to evolve in reaction to architectural design. One challenge at this time was the rising popularity of Atria. These are effectively large-scale chimneys, opening up buildings on all floors, and therefore were viewed by the authorities with jurisdiction, with deep suspicion. They occasioned a whole vein of research, testing and numerical analysis, into how smoke travels and how architectural arrangements should respond to this. Sprinklers are no use in high spaces, making mechanical systems necessary to remove smoke. Although these principles could be applied to multiple atria, this was still a decade of bespoke projects to solve complex architecture or engineering projects.
THE NINETIES AND INDUSTRY RECOGNITION It was perhaps during the nineties that fire safety engineering began to receive the industry recognition it deserves. Later in this decade, saw the introduction of the design and build procurement route, whereby the design and construction services are contracted by a single entity known as the design–build contractor. It was considered to be a procurement route that minimised risks for the project owner and could reduce the delivery schedule by overlapping the design phase and construction phase of a project. Some design- build contractors started to see the value fire safety engineering could add to their propositions because from their perspective, the application of performance based designs could bring cost savings to the project. The mid-nineties onwards also saw increasing economic growth in the UK and government investment in large-scale infrastructure projects. This was the decade when there was also an increasing level of private investment funding in major infrastructure projects. In 1994 the Channel Tunnel opened. Infrastructure projects like this were central to government plans to improve city connections and reduce urban populations. Transport interchanges became destinations, incorporating hotels, leisure facilities and retail outlets. These projects, above and below ground, fell outside existing building codes entirely, making a risk-based fire engineering approach central to their development. However, the fire engineering profession also continued to learn from practical experience. The decade witnessed several tunnel fires, each of which bettered engineers’ understanding of fire’s unique behaviour in
Image credits: (Opposite) Mass motion image, ©Oasys, (above) The Heron Tower, ©Hufton+Crow
tunnel environments. These characteristics being increased severity of temperature and quantity of smoke produced. Codes and standards had to be updated to represent the new understandings from these significant events – which were observed to be of a fire size ten or 20 times that originally expected. In a fire safety design approach, an appropriate means of escape had to be provided - and over long distances. For long tunnels and large underground stations this meant providing escape shafts, access points for the fire service, areas of refuge, smoke ventilation systems and detection to provide early warning. A well-coordinated emergency plan became essential for managing the response in the event of a fire. When such fire incidents happen, they bring safety onto the public and political agenda. Investigations into the 1996 Channel Tunnel fire, for example, revealed the need for upgraded detection systems on-board vehicles, additional training for operators in handling emergencies, and improved communication between drivers and control centres regarding emergencies.
THE NOUGHTIES: BEYOND STRUCTURAL ENGINEERING Such events also drew attention to the complexity of human behaviour in emergency situations. In the past, fire engineering typically
assumed human behaviour to be homogenous and/or optimal. For example people start evacuating immediately, on their own accord and will distribute themselves evenly between all exits. However, analysis of human behaviour in a number of real incidents indicates the contrary, that this is often suboptimal and non- homogenous. One of the most revealing pieces of behavioural analysis in this area was that conducted following the World Trade Center attacks in 2001. This suggested that occupant pre- evacuation behaviour is influenced by a number of factors, including past experience, existing social structures, and peoples’ ability to find out guidance on what to do during an incident. Individuals who had previously experienced the World Trade Center Bombings in 1993 for example, began evacuating prior to the official call occurred. Contrary to what might be believed, people also behave rationally and often altruistically. In this instant a number of people were reported to have assisted disabled strangers with traversing the stairs. Such findings have informed the development of fire engineering tools and methods to consider human behaviour in fire. This includes the development of more sophisticated evacuation models and their greater consideration within fire strategies. Although data analysis at present is typically focused on quantifying observed phenomena
July 2014 Architects Choice 33
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