【正文】 o remain on the refuge floor For residential buildings, Lo and Will (1997) believe that refuge floors may be necessary to provide an area of safety if conditions bee untenable due to long premovement times. Another approach to using refuge floors is to reduce the effective height of highrise buildings (Teh, 1994). Since the height is directly proportional to egress time, the provision of adequately protected refuge areas can reduce the effective building XX建筑大學畢業(yè)設計外文文獻及翻譯 12 height. Therefore once occupants have reached a refuge floor they can be considered to be safe. To achieve this The (1994) proposes the following requirements: ??Additional provisions to prevent smoke infiltration (smoke stopping of all vertical shafts) ??All lifts connecting to the refuge floor to be accessible through smoke lobbies ??The refuge floor must be accessible at all times and capable of acmodating the projected number of people ??A substantial part of the refuge floor is to be natural vented or capable of being naturally vented (ideally the refuge area should be a part of an external area) ??The design and layout of exit stairs should discharge occupants into the refuge floor before they proceed further down ??Pressurisation of exit stairs can be separated into vertical zones to avoid failures of the system affecting the whole stair Refuge floors in apartment buildings may assist the evacuation of occupants, but requirements of refuge floors need to be assessed against: other fire safety measures, the cost of a refuge floor and the emergency strategy. With the provision of sprinklers, partmentation and smoke control, the need for a refuge floor in apartment buildings is questionable. Apartment buildings are generally fire separated between individual units, at each floor level and between escape paths. The areas that are fire separated from each other could be designed as refuge areas reducing the need for an entire refuge floor. Occupants also have option to remain in their apartments, where they have access to fresh air from windows. The cost of a refuge floor also needs to be considered in conjunction with the cost of other fire safety systems. The opportunity cost of a refuge floor is the: loss of rental space, loss of real estate and cost of maintaining the floor. These cost could easily outweigh the cost of a sprinkler system that may provide a higher level protection. In highrise buildings fires, where smoke control systems have failed, a refuge floor with adequate natural cross ventilation, could have assisted occupant egress. The World Trade Centre bombing (Fahy and Proulx, 1996) and the MGM Grand fire (NFPA, XX建筑大學畢業(yè)設計外文文獻及翻譯 13 1982a) are two possible cases where injury and fatalities may have been avoided, if the occupants were able to get to a refuge floor with adequate ventilation. In these two fires, exits were promised by smoke and occupants were evacuating through poor conditions. In ultra highrise buildings, defined as greater than 40 storeys (Lo and Will, 1997), refuge floors could be of some assistance for disabled, elderly and other occupants who need assistance to evacuate. However, these occupants may be better served through refuge areas on each floor or by the occupants remaining in their apartments. Lo and Will (1997) argue that refuge areas do not have the same psychological benefits for the escaping occupants, as a refuge floor, and therefore are not as effective. Refuge areas The Acceptable Solutions to the NZBC (BIA, 1991) require refuge areas in apartment buildings greater than 58m high with intermediate floors. These refuge areas are to be located at intervals of no greater than 3 floors in the vertical safe paths, be at least 800mm wide and have an area of no less than 2m2. Guidance on refuge areas is also provided in British Standard BS5588 Part 8, 1998 (BSI, 1988). The NFPA Life Safety Code (Cote, 1997) requires people with severe mobility impairment to have at least two means of accessible egress. One method to achieve this is through the provision of a pliant refuge area. ??The effectiveness of refuge areas is highly dependent on the design details. Some of details that need to be considered are fire exposure, reliability of the smoke control system, outside wind and temperature condition. Without pressurisation all refuge areas can be subject to lethal failure (Nelson, 1993 and Klote, 1993). ??In many cases, the people needing the refuge areas may be unable to reach the area before their pathways bee untenable (Nelson, 1993 and Klote, 1993) ??The organisation and human behaviour problems involved with refuge areas are more plex (Nelson, 1993 and Klote, 1993). ??The operation of a sprinkler system eliminates the life threat to all occupants and can provide superior protection for people with disabilities as pared to a XX建筑大學畢業(yè)設計外文文獻及翻譯 14 refuge area. (Nelson, 1993 and Klote, 1993) Klote (1993) found pressurisation of refuge areas could be significantly influenced by, opening and closing of doors, window breakage and external wind pressures. Generally, refuge areas can be effectively pressurised by a direct pressurisation system or an indirect pressurisation system using lift shafts. But an indirect pressurisation system using the stairwell may not be effective or appropriate (Klote, 1993). Lifts The use of lifts or elevators for emergencies is not a new concept, but they are typically only used with fire brigade assistance. In general, occupants are told not to use lifts in a fire. However, the fire brigade has often used lifts to rescue people and mobilise equipment. Lifts have also been used in hospitals to move nonambulatory patients. The use of lifts for fire fighting and assisting rescue operations provides an efficient means of moving people and equipment. This