The development of a full probabilistic risk assessment model for quantifying the life safety risk in buildings in case of fire

In het kader van dit onderzoek is een probabilistisch model ontwikkeld dat het brandveiligheidsniveau van een gebouwontwerp kan kwantificeren en dit berekende veiligheidsniveau kan evalueren aan de hand van een vooraf gedefinieerd aanvaardbaar risicocriterium. De ontwikkelde methodiek kan zowel prescriptieve als op prestatie-gebaseerde ontwerpmethoden objectiveren door rekening te houden met de onzekerheid van ontwerpparameters en de betrouwbaarheid van veiligheidssystemen. Het model bestaat uit zowel een deterministisch als een probabilistisch gedeelte. Het deterministische kader is opgebouwd uit verschillende deelmodellen om zowel de verspreiding van brand en rook, als de interactie met evacuerende personen te simuleren. Verschillende deelmodellen zijn ontwikkeld om het effect van geïmplementeerde veiligheidsmaatregelen zoals detectie, sprinklers , rook- en warmteafvoersystemen, enz. mee in rekening te brengen. Het probabilistische kader is opgebouwd uit modellering van responsoppervlakken, steekproeftechnieken en ontwerp van grenstoestanden. De methodiek maakt gebruik van deze technieken om de nodige rekenkracht te beperken. Het uiteindelijke resultaat wordt vertaald naar een kans op sterfte, een individueel risico en een groepsrisico. De grote meerwaarde van de ontwikkelde methodiek is dat het mogelijk wordt om verschillende ontwerpmethodieken objectief met elkaar te vergelijken en het positieve effect van verbeterde veiligheidstechnieken en redundantie mee in rekening te brengen in het eindresultaat

Bandwidth-aware distributed ad-hoc grids in deployed wireless sensor networks

Nowadays, cost effective sensor networks can be deployed as a result of a plethora of recent engineering advances in wireless technology, storage miniaturisation, consolidated microprocessor design, and sensing technologies. Whilst sensor systems are becoming relatively cheap to deploy, two issues arise in their typical realisations: (i) the types of low-cost sensors often employed are capable of limited resolution and tend to produce noisy data; (ii) network bandwidths are relatively low and the energetic costs of using the radio to communicate are relatively high. To reduce the transmission of unnecessary data, there is a strong argument for performing local computation. However, this can require greater computational capacity than is available on a single low-power processor. Traditionally, such a problem has been addressed by using load balancing: fragmenting processes into tasks and distributing them amongst the least loaded nodes. However, the act of distributing tasks, and any subsequent communication between them, imposes a geographically defined load on the network. Because of the shared broadcast nature of the radio channels and MAC layers in common use, any communication within an area will be slowed by additional traffic, delaying the computation and reporting that relied on the availability of the network. In this dissertation, we explore the tradeoff between the distribution of computation, needed to enhance the computational abilities of networks of resource-constrained nodes, and the creation of network traffic that results from that distribution. We devise an application-independent distribution paradigm and a set of load distribution algorithms to allow computationally intensive applications to be collaboratively computed on resource-constrained devices. Then, we empirically investigate the effects of network traffic information on the distribution performance. We thus devise bandwidth-aware task offload mechanisms that, combining both nodes computational capabilities and local network conditions, investigate the impacts of making informed offload decisions on system performance. The highly deployment-specific nature of radio communication means that simulations that are capable of producing validated, high-quality, results are extremely hard to construct. Consequently, to produce meaningful results, our experiments have used empirical analysis based on a network of motes located at UCL, running a variety of I/O-bound, CPU-bound and mixed tasks. Using this setup, we have established that even relatively simple load sharing algorithms can improve performance over a range of different artificially generated scenarios, with more or less timely contextual information. In addition, we have taken a realistic application, based on location estimation, and implemented that across the same network with results that support the conclusions drawn from the artificially generated traffic

Construction site evacuation safety: Evacuation strategies for tall construction sites: Research report

BACKGROUND: The soaring scale of high-rise building construction – the number of projects and the size of the buildings – is reflected in the number of workers exposed to these demanding construction environments, and the potential for large-scale evacuation. In London alone, an estimated 541 highrise building projects are planned for the next few years. A typical project, such as the ￡400 million ‘100 Bishopsgate’ building, will have a peak of around 1,500 workers on site, and a cumulative workforce estimated at 12,000. The total number of workers exposed to construction sites in London during the lifetime of these 541 construction projects could easily exceed three million people. AIMS: The overall aim of the project is to improve the safety of construction site workers during on-site emergency evacuation, through the development of a unique evidence base characterising, for the first time, the actual performance and behaviour of construction workers during emergency evacuation. Combining this information with computer simulation will inform the development of more reliable evacuation procedures, improving the work environment through better preparation for, and management of, on-site emergency evacuation, and advancing the safety of construction workers. METHODOLOGY: The project consisted of four full-scale evacuation trials of two different high-rise buildings at two stages of construction, and five walking speed experiments. In total, 1,078 participants were involved in the nine trials, generating a data-set of around 2,200 data points, and information from 61 worker questionnaires. Analysis of this data produced generalised distributions for response times, walking speeds, stair speeds and ladder speeds, which were used to calibrate and validate the buildingEXODUS evacuation model. The validated model was then used to run 1,900 simulations exploring the impact on evacuation efficiency of changes to occupant response time, replacing formwork ladders with temporary stairs, and the use of hoists for evacuation. RESULTS: 31 key findings from this analysis were produced: • questionnaire analysis – eight key findings • generalised response time (RT) analysis relating to the formworks – five key findings • generalised RT analysis relating to the main building – three key findings • generalised climbing/walking speeds on ladders, temporary stairs and floor surfaces – four key findings • validation analysis – four key findings • use of the validated evacuation model to explore improvements in evacuation performance – seven key findings. CONCLUSIONS: The project has developed a unique evidence base characterising, for the first time, the actual performance and behaviour of construction workers during emergency evacuation. It consists of (i) response times for workers in the main building and the formworks, as measured from the sounding of the alarm in the main building, (ii) worker walking speeds on different types of surfaces, such as concrete, decking and decking with rebar, and (iii) worker ascent and descent speeds on temporary dogleg and parallel scaffold stairs and ladders. The data has been incorporated in the building evacuation simulation tool buildingEXODUS, providing it with a unique capability to simulate evacuation from high-rise construction sites. The performance of the software has been validated using measured data collected from the trials. The validated software has been used to explore how evacuation procedures for high-rise construction sites can be improved, including the impact of reducing worker response times, replacing ladders with temporary scaffold stairs within the formworks, and using hoists to assist in evacuation