No description available.

No description available.

As computing power increases and data relating to elementary chemical and physical processes improves, the use of computational modelling as a design tool in environmental and safety engineering is becoming increasingly important. Sensitivity analysis (SA) and uncertainty analysis (UA) can help to gain a better physical insight into the model and they can highlight possible discrepancies between experimental results and model predictions. Global methods are the best approach for this purpose, however using current methodologies their calculation consumes large amounts of computational effort.

With the increased complexity and higher safety commitment of modern safety–critical systems, safety assessment models of these systems are increasingly complicated and obscure. In practice, however, there is insufficient guidance on how to improve the understanding and evaluation of these models, while they are often used as important items of evidence in safety cases. This significantly threatens the confidence we can have in the soundness of safety cases. In this thesis, a coherent, structured approach to establishing confidence in safety assessment evidence is developed. Firstly, a means for the structured documentation of the core data elements of safety assessment models is defined, to support the development of both primary safety arguments and confidence arguments. Secondly, a model of evidence is developed to support the interfacing of safety assessment evidence with safety arguments. Thirdly, a structured cross-model inconsistency analysis method is proposed as a means of scrutinizing potentially inadequate models. Finally, an expanded argument construction process is established to add rigour to safety case development, and a number of argument patterns are designed to guide and inspire structured justification of the adequacy of safety assessment models as evidence for safety critical systems. The evaluation of the approach is carried out primarily through examples and cases studies. It is demonstrated that the approach is feasible and the confidence issue in safety assessment evidence is addressed more explicitly and more rigorously by using the approach.

No description available.

No description available.

No description available.

The use of tin oxide, zinc stannate and zinc hydroxystannate as flame retardants and smoke suppressants in both halogenated and nonhalogenated polyester resin thermosets has been investigated. Oxygen Index studies showed that zinc stannate in conjunction with the resin based on dibromoneopentyl glycol (DBNPG) was the most efficient combination. This was also the case when the same resin containing less bromine was used (10% instead of 28.3%). It was however the tin oxide which caused the greatest decrease in smoke production. Nitrous Oxide Index tests showed the tetrabromophthalic anhydride (TBPA) and chlorendic anhydride (HET) resins to burn via a vapour phase mechanism and the DBNPG resin to burn via a condensed phase mechanism. Thermogravimetry indicated that the tin oxide did not interact with any of the resins, the additive being recovered almost quantitatively after degradation in air. The Zn/Sn additives interacted with the DBNPG resin with additive being almost completely lost every time. Some interaction was observed with the HET and TBPA resins but this was to a much lesser extent. XRD results indicated the possible formation of tin bromide from a DBNPG sample containing zinc hydroxystannate and this finding would support the theory of a condensed phase mechanism for the DBNPG resin. The SEM photographs indicated the formation of allne powdery layer on the surface of the burnt sample. Elemental analysis by. SEM showed that this contained both zinc and tin, as did the smoke. Residue analysis gave some indication of the temperature at which metal and halogen were volatilised from each sample. The results suggested that for the DBNPG resin with the Zn/Sn additives, it is very likely that tin bromide could be formed as both the tin and bromine are lost in the same temperature ranges. The same could be said for the TBPA resin but to a much lesser extent but for the HET resin it is unlikely that tin chloride could be formed as the volatilisation temperatures do not coincide. In conclusion, a condensed phase mechanism is proposed for the DBNPG resin with the Zn/Sn additives incorporated. It is suggested that this involves the formation of tin bromide which is then hydrolysed in the flame to yield tin oxide and hydrogen halide which can then act as a radical trap and suppress the flame reactions.

No description available.

Recent fire tests on the Cardington full-scale test frame and observations from real fires have demonstrated the significance of connections in fire, when they can have beneficial effects on the survival time of the structure. The lack of experimental data on the behaviour of steel and composite connections in fire means that this is insufficiently addressed in current design codes and also limits the effective use of numerical models. However, recent experimental tests on small-scale specimens have shown that it is possible to derive accurately the moment-rotation relationships at elevated temperature and have established the principles by which this could be achieved. In order to extend the scope to include further parameters, five series of tests have been carried out in a portable connection furnace at the Building Research Establishment. The test series includes flush and flexible end-plate bare-steel connections, and flexible end-plate composite connections. The testing procedure and the resulting behaviour are described. The fire test temperature profiles across the connections are detailed and the connection failure mechanisms are discussed. From the test results, moment-rotation- temperature curves for different connection types are derived. The degradation of connection characteristics is compared with that of structural steel. The experimental behaviour is also compared with the results obtained from an existing finite element analysis developed to model connection response in fire conditions. The experimentally derived connection characteristics have been incorporated within a parametric study of a typical sub-frame, to study the effect of connection type, end-plate thickness, concrete strength, load ratio, and connection temperature. Analysis is extended to a three-dimensional sub-frame. The patterns of behaviour observed in the connection tests is compared with that of the connections in the large-scale fire tests on the composite building at BRE's Cardington laboratory. Based on knowledge about the behaviour of connections at elevated temperature, a component-based model is developed for the elevated temperature response for flexible end-plate connections, both as bare-steel and composite. This is based on the response of constitutive parts of connection. The model is easy to use, and capable of modelling the entire non-linear range of connection behaviour. The predicted response is compared with that recorded experimentally.