土木工程外文翻譯---建筑防火設計-建筑結構(編輯修改稿)

　

【文章內容簡介】 nd access openings between the adjacent partments (doors and stairs). Fire spread via the external openings (windows) is a distinct possibility given a fully developed fire. Limit ing the window sizes and geometry can reduce but not eliminate the possibility of vertical fire spread. By far the most effective measure in limiting fire spread, other than the presence of 7 occupants, is an effective sprinkler system that delivers water to a growing fire rapidly reducing the heat being generated and virtually extinguishing it. Estimating Fire Severity In the absence of measures to extinguish developing fires, or should such systems fail。 severe fires can develop within buildings. In fire engineering literature, the term “fire load” refers to the quantity of bustibles within an enclosure and not the loads (forces) applied to the structure during a fire. Similarly, fire load density refers to the quantity of fuel per unit area. It is normally expressed in terms of MJ/m2 or kg/m2 of wood equivalent. Surveys of bustibles for various occupancies ( offices, retail, hospitals, warehouses, etc)have been undertaken and a good summary of the available data is given in FCRC (1999). As would be expected, the fire load density is highly variable. Publications such as the International Fire Engineering Guidelines (2020) give fire load data in terms of the mean and 80th latter level of fire load density is sometimes taken as the characteristic fire load density and is sometimes taken as being distributed according to a Gumbel distribution (Schleich et al, 1999). The rate at which heat is released within an enclosure is termed the heat release rate (HRR) and normally expressed in megawatts (MW). The application of sufficient heat to a bustible material results in the generation of gases some of which are bustible. This process is called pyrolisation. Upon ing into contact with sufficient oxygen these gases ignite generating heat. The rate of burning(and therefore of heat generation) is therefore dependent on the flow of air to the gases generated by the pyrolising flow is influenced by the shape of the enclosure (aspect ratio), and the position and size of any potential openings. It is found from experiments with single openings in approximately cubic enclosures that the rate of burning is directly proportional to A h where A is the area of the opening and h is the opening height. It is known that for deep enclosures with single openings that burning will occur initially closest to the opening moving back into the enclosure once the fuel closest to the opening is consumed (Thomas et al, 2020). Significant temperature variations throughout such enclosures can be expected. The use of the word ?opening? in relation to real building enclosures refers to any 8 openings present around the walls including doors that are left open and any windows containing non fireresistant is presumed that such glass breaks in the event of development of a significant fire. If the windows could be prevented from breaking and other sources of air to the enclosure limited, then the fire would be prevented from being a severe fire. Various methods have been developed for determining the potential severity of a fire within an are described in SFPE (2020). The predictions of these methods are variable and are mostly based on estimating a representative heat release rate (HRR) and the proportion of total fuel ? likely to be consumed during the primary burning stage (Figure 4). Further studies of enclosure fires are required to assist with the development of improved models, as the behaviour is very plex. Role of the Building Structure If the design objectives are to provide an adequate level of safety for the occupants and protection of adjacent properties from damage, then the structural adequacy of the building in fire need only be sufficient to allow the occupants to exit the building and for the building to ultimately deform in a way that does not lead to damage or fire spread to a building located on an adjacent objectives are those associated with most building regulations including the Building Code of Australia (BCA). There could be other objectives including protection of the building against significant damage. In considering these various objectives, the following should be taken into account when considering the fire resistance of the building structure. NonStructural Consequences Since fire can produce smoke and flame, it is important to ask whether these outes will threaten life safety within other parts of the building before the building is promised by a loss of structural adequacy? Is search and rescue by the fire brigade not feasible given the likely extent of smoke? Will the loss of use of the building due to a severe fire result in major property and ine loss? If the answer to these questions is in the affirmative, then it may be necessary to minimise the occurrence of a significant fire rather than simply assuming that the building structure needs to be designed for high levels of fire resistance. A lowrise shopping centre with levels interconnected by large voids is an example of such a situation. Other Fire Safety Systems 9 The presence of other systems (. sprinklers) within the building to minimise the occurrence of a serious fire can greatly reduce the need for the structural elements to have high levels of fire resistance. In this regard, the uncertainties of all firesafety systems need to be considered. Irrespective of whether the fire safety system is the sprinkler system, stair pressurisation, partmentation or the system giving the structure a fireresistance level (. concrete cover), there is an uncertainty of performance. Uncertainty data is available for sprinkler systems(because it is relatively easy