Failures of natural gas transmission pipelines have occasionally occurred around the world. Ignited releases from ruptured high-pressure transmission pipelines produce a highly transient thermal radiation field in the initial stages, as described in papers presented at IPC previously. In the context of risk assessment, modeling the effects of fires on buildings is as important as modeling the thermal radiation field. A simplistic approach may not be appropriate, particularly when there is a significant difference in thermal radiation levels between the nearest and the furthest points of the building from the fire. It is necessary to consider the timescales involved, such as the timescale for fire spread through the building, for the evacuation of people and for the external thermal radiation field to decline. All of these factors need a modeling approach that is commensurate with other uncertainties in the risk analysis. The purpose of this paper is to describe a general modeling approach to assess the effects of transient fire loading on such large buildings. Illustrative examples are given for a large two-storey building and an apartment block. The effects of parameter variations, such as changes in the rate of flow of people through a doorway and the rate of progress of people from one floor to the next, are demonstrated. The results help to establish a method for evaluating the risk to occupants of large buildings. This can be used to support informed decisions on pipeline safety issues and in prioritizing integrity management programs on a risk basis.

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