Applying the New Zealand Performance Based Design Fire Framework to Buildings Designed in Accordance with NFPA5000

Abstract

A framework for performance based fire design is in the process of being developed by the Department of Building and Housing and such a framework may become a compulsory methodology for performance based fire design in the future. The framework has been developed with the intention of providing a similar level of safety to a building as if the building is designed in accordance with the New Zealand compliance document C/AS1. Ten design fire scenarios have been included in the framework to ensure buildings will be challenged. Design fires for particular building uses, tenability criteria for occupant safety, detector criteria to determine detection time and pre-movement time for egress calculation have been specified in the framework.

In order to provide a comparison of the framework against the international building code, three complex case studies have been applied to buildings designed in accordance with NFPA5000 and investigated using the input values and methodologies described in the framework. The case study buildings selected are a retail warehouse, a hospital and a shopping mall. The selection of the buildings was based on complexity of building layout, likelihood of rapid fire growth and high occupancy.

Zone modelling (BRANZFIRE modelling) and Computational Fluid Dynamics (Fire Dynamic Simulation modelling) have been utilised in an Available Safe Egress Time (ASET) and Required Safe Egress Time (RSET) analysis. Results of the research showed that the framework provided a robust and consistent method for performance based fire design and the guidance provided in the framework gave a clear methodology to determine the ASET and the RSET. In additional, the framework provided an even more restrictive requirement than the prescriptive requirement in the NFPA5000 in relation to external walls fire resistance and mezzanine floor fire resistance. Conversely, it provided a too relaxed requirement than the prescriptive requirement in the NFPA5000 in relation to means of egress and fire/smoke compartmentation.