Salvatore Ancona
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那你看过吗？结构和土木工程师一直在努力创建将彻底改变建筑业的下一个新产品。手指连接的木桁架当然并不是什么新鲜事物，实际上它们自1989年以来一直存在。多年来，建筑社区中的产品进出。每当消防员讨论平行的和弦木桁架时，他或她会自动恢复带有金属板连接器或毛刺的木桁架，并将所有这些结构元素与该产品相关联。就工程木产品（EWP）而言，有许多不同的产品可供消费者使用，因此重要的是要跟上趋势。Finger Toded Wood桁架是一种设计用于住宅/轻型商业应用的工程木材产品（照片1），它们的外观越来越多。在获得干草叉之前，让我们讨论他们的建筑，应用，阻力和关注点。
Finger joints have been around since early Egyptian times. They are used today in an engineering application to join lumber products together to achieve certain lengths while maintaining structural stability. When we see them used as floor or rood joists we automatically think it’s got to be weaker…right? Now I’m no fan of engineered wood products as a whole but there are aspects to some products that can replicate their dimensional wood counterparts. Finger jointed wood trusses are composite in nature, meaning they use two or more different materials to achieve the desired strength or use. The two materials are lumber and adhesive (photo 2).
The top chord and bottom chords are usually 2×3 with the web members comprised of smaller dimensions. The finger joints are precut into the chords and web members (photo 3). They are later seated tightly into the joints and secured via adhesive. Many have indicated that the use of engineered products such as this is due to money savings. This is not accurate. In fact, finger jointed wood trusses can be as much as three times more expensive than their dimensional lumber counterparts. What is evident however is that their usage is primarily based on the homeowner. They provide the homeowner with a stronger product that can achieve the longer span that the homeowner desires. Open floor plans are the in thing now, so plan on seeing these engineered materials more and more.
非常关注的是工程材料中使用的粘合剂。许多人认为所使用的粘合剂或胶水是易燃，可燃的，或者它们在火灾条件下融化或软化。这可能是在很多年前确实如此，但是今天使用的粘合剂比他们支持的木材更具弹性，有时甚至更强。指的接头木桁架使用溶质醇粘合剂（Resorcinol造型）。传统上由于其耐水性而用于海洋应用中。在木材应用中，已经表明，在火灾条件下，异霉素粘合剂比木材更强，温度在1,100°F后降解。溶酶醇粘合剂在热量下不会分层，并且不会融化。基于可用文献，与平行和弦木桁架中的金属板连接器不同，粘合剂无助于燃烧或提早失败。
成员应意识到，手指连接的木桁架仍然是工程材料，在工厂，运输，储存和安装中易受其建筑物的影响。如果未正确应用粘合剂，则在Web成员失败的情况下，负载可能不适当地转移。手指连接的木桁架自下而上。底部的和弦首先失败，因此可以像木头束一样下垂，但这并不总是很明显。消防旅行是这里的全景。与所有开放的网络概念一样，火灾可以在网络成员中不受阻碍并消耗整个地板系统。由于公用事业的安装，可能会损坏Web成员，这会导致负载不成比例。许多防火性测试是第三方或私人测试，因此在固有的防火性或手指接头木桁架的结构稳定性时，没有太多信息在被火攻击时。与往常一样，消防员必须保持警惕，并在这些材料受到火灾攻击并尽早解决时监视条件。每当很明显的是，手指的木桁架受到大火攻击，成员应立即解决。 In addition, fires involving unprotected finger jointed wood trusses should be checked early and construction should be monitored.
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。
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