Temporary bracing for small trusses
我正在安装具有20'跨度，2'悬垂的标准桁架，并为简单的山墙屋顶安装4:12的音高。桁架图表明，唯一需要的永久性支撑是顶部和直接安装在底部的干墙天花板，我将安装两者。但是，通用的安装说明BCSI-B1，一个带有桁架的单个单表文档，需要五种不同类型的临时支撑：顶部和弦和底部和弦上的侧向和对角线，以及网络上垂直方向的对角线，这是我完全理解的，因为它可以防止货架立即发生。If I were going to climb around on the trusses before they’re sheathed, I could see why more bracing would be needed, but I’m planning to install the first row of sheathing, in full 4×8 sheets, on each side from a ladder and then each subsequent row from atop the sheathing already installed. The much longer BCSI booklet on truss installation frequently says to refer to the truss drawings. I would not take any chances with safety, but if some of temporary bracing in the installation instructions won’t be of any benefit for trusses as small as mine that I won’t be climbing upon and that don’t require any additional lumber for permanent bracing, I’d rather save whatever time, wood, and nails I safely can. In real-world practice, for small trusses like mine, which of these five types of temporary bracing are actually installed?
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答复
杰夫，
我不会建议您忽略桁架图，但这是我像您描述的桁架一样小的桁架。
假设外墙有支撑：
- Lay the gable truss flat and support it with several props, and sheath it.
- 将A 2“ x4”钉在跨度中央的墙壁上，延伸几英尺，站立山墙桁架并将其固定在2“ x4”和下面的墙壁上。
- 另外三个桁架，将它们保持直立，并在峰值上撑一下。
- 支撑跨度中间的底弦。
- 从山墙桁架的峰值到底部和弦支架，将对角线支架运行。
此时，桁架应该是坚固的。
- 从那时起，只有在峰值上支撑桁架。
非常感谢，马尔科姆！
我很高兴听到您在施工期间认真对待您的安全。
If you are in an area subject to high winds or earthquakes, I would consider additional bracing as cheap insurance. The small cost of lumber and nails for extra bracing is nothing compared to the more costly damage to finish materials after the house is complete. Also a fire is more damaging to trusses than solid lumber roof framing, so again some extra bracing would help, though unlikely needed. (Ask a fireman about the additional danger of fighting a building fire when there's a truss roof.) Finally, if your sheathing does rot decades later, there goes some of your lateral and diagonal support of the trusses. I'd guess that diagonal support from end truss peak to the bottom cord of a truss 4' interior might be the most useful to add to sheathing support, but I'm no structural engineer.
制造商推荐的支撑可能会使桁架制造商的任何保修无效，这可能远远超过几个2x4的成本。避免设计自己的桁架支撑和支撑的诱惑。
罗伯特和鲍勃,
杰夫（Jeff）或我都没有建议在桁架图纸上省略要求的支撑。他的问题是：在所有桁架安装图上显示的多少通用临时支撑是20英尺4/12山墙屋顶所需的？这是一旦桁架鞘的支撑即可去除的。