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It is evident that numerical methods have a useful role in the assessment of welding conditions for the safe in-service welding of high-pressure gas pipelines. No published work has considered the direct calculation of burn-through using a combination of thermal and stress analysis. Using empirical relationships between welding process parameters and weld bead size and shape is an appropriate way of defining the weldment geometry and the heat-source coordinates. With this approach, adequate agreement between predicted weld penetration, weld cooling times and heat-affected zone hardness has been made. Following the prediction of a thermal field a full thermo-elastic plastic model can be used to predict the conditions likely to cause burn-through. In this paper two significant research aspects of in-service welding have been addressed, as follows: 1 A new mathematical description of a heat source to represent the common in-service welding process, i.e. vertically up and vertically down manual metal arc welding with hydrogen controlled electrodes has been formed and has given good correlation with experiment and field welds. 2 Preliminary burn-through modelling of in-service welding using non-linear thermal-stress numerical methods has given encouraging results.

The gold standard for complying Performance Requirements is based on a Quantitative Probabilistic Risk Assessment (QPRA) method. This case study demonstrates the application of this approach to performance based design of a six-storey commercial building with an open stair interconnecting four storeys. Computational Fluid Dynamics (CFD) based and zone fire as well as evacuation simulations are used to quantify consequences whilst detailed event trees underpinned by statistical data and analysis are utilised to calculate corresponding probabilities. Results are combined in a trade-off analysis tool which calculates the Expected Risk to Life (ERL) based on the trial design features included in each design option. The approach was used to determine a preferred design that achieves an acceptably low ERL and compliance with the Performance Requirements of the Building Code of Australia (BCA). The benchmark ERL was set as 1.36 deaths/1000 fires or a probability of death from a fire of 1.36 x 10-3 based on local statistical data. To obtain an optimum fire safety design (Alternative Solution) a layered approach was adopted in which fire safety systems were added until the risk to occupants in the building due to a fire is the same or less than the benchmark ERL. Eventually three sets of trial design were considered and in all cases the calculated ERL were roughly 22% lower than the benchmark. Eventually the trial design with the least number of fire safety systems were recommended as the Alternative Solution. The trade-off analysis shows the sprinklers and wallwetting sprinklers in the office area resulted in a 20-fold difference in the building wide ERL, each. Schematic Design Fire Specification Event Tree Development Preliminary Risk Assessment and Scenario Generation Data Collection/Analysis Collect and analyse relevant data Determine credible fire scenarios (causes, locations, etc.) Conduct preliminary, qualitative risk analysis Complete risk ranking and short list design fire scenarios Identify all possible statuses of fire safety subsystems Construct event tree and generate possible outcomes Calculate probabilities using relevant data