【正文】 ding. The ability to influence the rate of fire starts and the resulting fire severity is unique to the consideration of fire within buildings since other loads such as wind and earthquakes are directly a function of nature. The possible approaches for designing a building for fire safety are presented using an example of a multistorey building constructed over a railway line. The design of both the transfer structure supporting the building over the railway and the levels above the transfer structure are considered in the context of current regulatory requirements. The principles and assumptions associ ated with various approaches are discussed. 1 INTRODUCTION Other papers presented in this series consider the design of buildings for gravity loads, wind and design of buildings against such load effects is to a large extent covered by engineering based standards referenced by the building regulations. This is not the case, to nearly the same extent, in the case of fire. Rather, it is building regulations such as the Building Code of Australia (BCA) that directly specify most of the requirements for fire safety of buildings with reference being made to Standards such as AS3600 or AS4100 for methods for determining the fire resistance of structural elements. The purpose of this paper is to consider the design of buildings for fire safety from an engineering perspective (as is currently done for other loads such as wind or earthquakes), 2 whilst at the same time,putting such approaches in the context of the current regulatory the outset,it needs to be noted that designing a building for fire safety is far more than simply considering the building structure and whether it has sufficient structural is because fires can have a direct influence on occupants via smoke and heat and can grow in size and severity unlike other effects imposed on the building. Notwithstanding these ments, the focus of this paper will be largely on design issues associated with the building structure. Two situations associated with a building are used for the purpose of discussion. The multistorey office building shown in Figure 1 is supported by a transfer structure that spans over a set of railway tracks. It is assumed that a wide range of rail traffic utilises these tracks including freight and diesel lootives. The first situation to be considered from a fire safety perspective is the transfer is termed Situation 1 and the key questions are: what level of fire resistance is required for this transfer structure and how can this be determined? This situation has been chosen since it clearly falls outside the normal regulatory scope of most build ing regulations. An engineering solution, rather than a prescriptive one is required. The second fire situation (termed Situation 2) corresponds to a fire within the office levels of the building and is covered by building regulations. This situation is chosen because it will enable a discussion of engineering approaches and how these interface with the building regulations–since both engineering and prescriptive solutions are possible. 3 2 UNIQUENESS OF FIRE Introduction Wind and earthquakes can be considered to be “natural” phenomena over which designers have no control except perhaps to choose the location of buildings more carefully on the basis of historical records and to design building to resist sufficiently high loads or accelerations for the particular location. Dead and live loads in buildings are the result of gravity. All of these loads are variable and it is possible (although generally unlikely) that the loads may exceed the resistance of the critical structural members resulting in structural failure. The nature and influence of fires in buildings are quite different to those associated with other“l(fā)oads” to which a building may be subjected to. The essential differences are described in the following sections. Origin of Fire In most situations (ignoring bush fires), fire originates from human activities within the building or the malfunction of equipment placed within the building to provide a serviceable environment. It follows therefore that it is possible to influence the rate of fire starts by influencing human behaviour, limiting and monitoring human behaviour and improving the design of equipment and its maintenance. This is not the case for the usual loads applied to a building. Ability to Influence Since wind and earthquake are directly functions of nature, it is not possible to influence such events to any extent. One has to anticipate them and design accordingly. It may be possible to influence the level of live load in a building by conducting audits and placing restrictions on contents. However, in the case of a fire start, there are many factors that can be brought to bear to influence the ultimate size of the fire and its effect within the building. It is known that occupants within a building will often detect a fire and deal with it before it reaches a sig nificant size. It is estimated that less than one fire in five (Favre, 1996) results in a call to the fire brigade and for fires reported to the fire brigade, the majority will be limited to the room of fire origin. In oc cupied spaces, olfactory cues (smell) provide powerful evidence of the presence of even a small fire. The add