Salvatore Ancona
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可能是火场上最危险的位置之一屋顶位置。屋顶消防员试图进入并在火灾袭击中访问建筑物的屋顶系统时，遇到了许多不同的障碍。经验丰富的消防员需要识别和分析危险的屋顶条件。正如在燃烧结构内部运作的消防员在试图接触潜在的受害者并通过抑制崩溃而努力工作一样，屋顶团队正在尝试使这些营救内部的条件在危险的烟囱上同时进行，同时又在危险的烟囱上进行比赛至少可以说。
弓弦桁架屋顶系统在20世纪中叶取得了进展。保龄球小巷，超市和自动车身维修店等空间的长距离跨越的能力已令人垂涎，以便在建筑物内自由移动，而无需使用柱子或承载墙。在消防服务界，这些结构代表了一个重大危险。有几次事件声称在上面或下方运行的多名消防员的生命。这是正确的，消防服务教育者已经确定了与弓箭桁架屋顶系统相关的风险。已收到该消息，成员们了解到，工作时间应受到限制或搁置在一起，以避免重大伤害或死亡。
相关的消防员培训
Construction Concerns: Trusses Revisited
这bowstring truss, also known as the arched rib truss, uses similar components to other truss systems such as the use of a top chord, bottom chord, struts, and ties. (Figure 1). Top chords are under compression, bottom chords are under tension, struts resist compressive forces, and ties resist tensile forces. There are some obvious differences, such as the curved or arched top chord, wider spacing between trusses, larger open spans (greater than 40 feet), dimensional joists used in conjunction with truss systems, and large masonry pilasters. Bowstring truss systems represent bridge-like architecture; they are architecturally beautiful and represent early ingenuity. They use wood or steel. When wood is used, you will often see large dimensional lumber, many times spliced together on the bottom chord with panel points using steel bolts and plates. (Figure 2). This enables the long span. The steel bowstring can be constructed with various steel forms, such as angle iron or square tubular members. The dangers associated with the systems are often similar in failure but different in global failure rates. Bowstring truss roofs can often be masked by high parapets. The National Lightweight Construction Research Project (1992) reveals that bowstring construction in ordinary constructed buildings (Type III) does not classify as lightweight construction.
很难证明在带有木桁架屋顶的结构内进行长时间的防御性消防操作是合理的。188金博网网址多少消防员应该预期屋顶的早期崩溃，并随后发生砖墙墙的失败。但是，如果木桁架受到防火材料的保护，则屋顶的塌陷会更慢，并且木桁架更有可能失效。重要的是要注意著名大火的崩溃时间。这华尔德鲍姆的超市屋顶单位到达后32分钟倒塌，the Hackensack Ford dealership roof collapse单位到达35分钟后D，在派遣后约16分钟内，2010年在一家以前的商业洗衣设施中发生了大火。虽然塌陷时间可能会根据条件而变化，但由于其大小和性质，大弓结桁架屋顶在灾难性上失败。尽管35分钟似乎很长时间，但请考虑一下这实际上是多长时间的。这意味着，在20分钟时，进步还不够大，无法保证继续屋顶运营，这对于许多部门来说，这是运营进度的经验法则。由于高高的天花板，烟雾，热和火灾可能很早就被发现，因此消防员在搜索内部时可能不会看到很大的风险。可能有轻度的烟雾状况，但上面肆虐。
When a bowstring truss system is attacked by fire, the connections are where we see early failure. Steel bolts and plates fail or become ineffective releasing the structural members. Because these truss systems are so widely spaced, when a bowstring truss releases, a large open span supporting the roof is dismantled, releasing wood joists above and causing a significant local collapse of that area. Bowstring trusses use cross ties and bracing because they are very unstable when not connected into a system. When the bracing and ties fail, it can cause a large truss to topple over laterally. The occupants also tend to use the truss loft within a truss as storage space, often loading up the bottom chord with excessive weight, which contributes to the unpredictable collapse nature, as seen in the Hackensack fire. It is important to note that heavy fire loads are often seen in buildings using bowstring truss construction. (Figure 3). One of the pictures below shows tire storage directly beneath the bottom chord of a large (60 foot) bowstring truss. The heat generated by potential fire within this space would be astronomical and failure of this truss could be much quicker than others. This does not mean that if one truss fails every single one would, but even a local collapse could have a horrible outcome for firefighters working above.
相关的消防员培训
在这样的建筑物中，我们需要分析风险与奖励，以使消防员进行垂直操作。该操作会受益于上方的消防员，尤其是在大火上受益吗？除了在内部运作的消防员外，内部运营是否没有其他生命危险？这些都应在您的标准操作程序中概述。如果在一定时间内不显着，则应预期崩溃。
尽管this post focuses on large fires with collapse, it is up to members and incident commanders to determine the best course of action for fires using in bowstring roofs. Not every building will collapse and not every roof is dangerous. In no way should we advocate entirely omitting operations on these roofs, because there are cases where it is perfectly safe. Also, check outNIOSH报告F2010-38，2011年7月6日，其中包含一项摘要，该摘要是由于弓箭屋顶倒塌而导致的死亡人数调查。
Salvatore Anconais a deputy chief fire instructor at the Nassau County (NY) Fire Service Academy; a former captain and training officer for the Bellmore (NY) Fire Department; and a paramedic supervisor in Queens, New York. He has an A.S. degree in fire science from Nassau Community College and is in the emergency services administration undergraduate program at John Jay College of Criminal Justice. Ancona is the author ofFacebook上的建筑施工页面“ Brannigan的儿子”并获得了2019年FDIC国际Honeywell Dupont奖学金的获得者。
