【正文】 to collect) but is not readily available for the other fire safety systems. This sometimes results in the designers and building regulators considering that only sprinkler systems are subject to uncertainty. In reality, it would appear that sprinklers systems have a high level of performance and can be designed to have very high levels of reliability. Height of Building It takes longer for a tall building to be evacuated than a short building and therefore the structure of a tall building may need to have a higher level of fire resistance. The implications of collapse of tall buildings on adjacent properties are also greater than for buildings of only several storeys. Limited Extent of Burning If the likely extent of burning is small in parison with the plan area of the building, then the fire cannot have a significant impact on the overall stability of the building structure. Examples of situations where this is the case are opendeck carparks and very large area building such as shopping plexes where the fireeffected part is likely to be small in relation to area of the building floor plan. Behaviour of Floor Elements The effect of real fires on posite and concrete floors continues to be a subject of much testing at Cardington demonstrated that when parts of a posite floor are subject to heating, large displacement behaviour can develop that greatly assists the load carrying capacity of the floor beyond that which would predicted by considering only the behaviour of the beams and slabs in situations have been analysed by both yield line methods that take into account the effects of membrane forces (Bailey, 2020) and finite element techniques. In essence, the methods illustrate that it is not necessary to insulate all structural steel elements in a posite floor to achieve high levels of fire work 10 also demonstrated that exposure of a posite floor having unprotected steel beams, to a localised fire, will not result in failure of the similar real fire test on a multistory reinforced concrete building demonstrated that the real structural behaviour in fire was significantly different to that expected using small displacement theory as for normal tempera ture design (Bailey, 2020) with the performance being superior than that predicted by considering isolated member behaviour. Prescriptive Approach to Design The building regulations of most countries provide prescriptive requirements for the design of buildings for requirements are generally not subject to interpretation and pliance with them makes for simpler design approval–although not necessarily the most costeffective provisions are often termed deemedtosatisfy (DTS) provisions. All aspects of designing buildings for fire safety are covered–the provision of emergency exits, spacings between buildings, occupant fire fighting measures, detection and alarms, measures for automatic fire suppression, air and smoke handling requirements and last, but not least, requirements for partmentation and fire resistance levels for structural members. However, there is little evidence that the requirements have been developed from a systematic evaluation of fire safety. Rather it would appear that many of the requirements have been added one to another to deal with another fire incident or to incorporate a new form of technology. There does not appear to have been any real attempt to determine which provision have the most significant influence on fire safety and whether some of the former provisions could be modified. The FRL requirements specified in the DTS provisions are traditionally considered to result in member resistances that will only rarely experience failure in the event of a is why it is acceptable to use the above arbitrary point in time load bination for assessing members in fire. There have been attempts to evaluate the various deemedtosatisfy provisions (particularly the fire resistance requirements)from a fireengineering perspective taking into account the possible variations in enclosure geometry, opening sizes and fire load (see FCRC, 1999).One of the outes of this evaluation was the recognition that deemedto satisfy provisions necessarily cover the broad range of buildings and thus must, on average, be quite onerous because of the magnitude of the above should be noted that the DTS provisions assume that partmentation works and that fire is limited to a single partment. 11 This means that fire is normally only considered to exist at one level. Thus floors are assumed to be heated from below and columns only over one storey height. PerformanceBased Design An approach that offers substantial benefits for individual buildings is the move towards performancebased regulations. This is permitted by regulations such as the BCA which state that a designer must demonstrate that the particular building will achieve the relevant performance requirements. The prescriptive provisions (. the DTS provisions) are presumed to achieve these requirements. It is necessary to show that any building that does not conform to the DTS provisions will achieve the performance requirements. But what are the performance requirements? Most often the specified performance is simply a set of performance statements (such as with the Building Code of Australia)with no quantitative level given. Therefore, although these statements remind the designer of the key elements of design, they do not, in themselves, provide any measure against which to determine whether the design is adequately acceptance criteria are now considered. Acceptance Criteria Some guidance as to the basis for acceptable designs is given in regulations such as the BCA. These and other possible bases are now considered in principle. (i)pare the levels of safety (with respect to a