Break a handle on a lawn mower, it's inconvenient (and the tubing for that is much larger and stronger than 1/2" EMT) break the conduit holding up you roof, and it's more than inconvenient! My lawn mower handles always break right where the tube is flattened at the point of attachment to the bracket. Yeah, I would question its use as collar tie material-for one thing, flatttening the ends will tend, I would guess, to "work harden" it and make it brittle, as well as making an area where stress will concentrate and make it likely to fail there. I was damn lucky it never split or shattered. Well, I used 1/2" conduit for a cannon barrel when I was young and (more) stupid. #RAFTER TIE SERIES#The folks at Simpson Strong Tie have an architectural series of brackets, so the guy who asked the original question should check into that and might find what he needs. Alternatively, spread the load out over several bolts. The best connection would be to make the steel bracket loop around the back of the rafter, so fasteners would only be needed to prevent the bracket from slipping up the rafter. The steel ultimately connects back to wood rafters, and that wood needs to take the entire tensile load of the steel tie. If you replace lots of wooden collar ties (which were safe due to redundancy and load sharing) with fewer steel ones, be very careful with the end connections. In most residential construction, wood can be used in tension and compression, because the loads are light and there are lots of pieces for redundancy. That's why collar ties and trusses are ok to be made of wood. Likewise, notice how the steel plates that sandwich built-up trusses have hundreds of fingers that grab the wood in an attempt to distribute the load through the most area.Īnother drawback of using wood in tension is that it can split at fasteners and lose all of its load carrying capability. If you look at a Simpson Strong Tie specification, you will see that the load ratings of the brackets are only valid if all of the required fasteners are installed. In tension, only the longitudinal cross sectional area of the nails or bolts transfer load to the wood. Wood works better in compression than in tension, mostly because we can utilize the entire end surface of the wood to carry the load, such as in a column. Steel often also has a grain direction, depending on how it is made, but properties are much more uniform and predictable for steel than for wood. #RAFTER TIE PLUS#Steel is a generic term, and there are thousands of types of steel, plus different heat treatments that yield different properties for each one. Wood is orthotropic, which means it has different properties depending on the direction of the grain relative to the direction of measurement of a property such as compressive or tensile strength. There are too many variables involved to make a blanket statement that Douglas Fir is stronger than "steel" by weight. once you have tension you tighten cable clamps close to attachment point and cutt off the excess. you have to make the cables long, and a temporary "eye" on the long end to be able to hook the come-a-long and apply tension. To do that you use the crosby clamps or cable clamps to make the "eye" on the ends of the cable. clamp down the cable at that point and then remove joist. make sure of the rafters connection at the wall also.īut once you have that figured out i would just make up the cables to the points at either end and then tighten the cables with a come-a-long untill you are relieving the tension on the joists. remember the rafters are usually tied to the joists or collar ties as well as the wall. you want to make sure it doesn't come loose there. The thing i would be most worried about is the attachment point. It should be i pretty simple job to do, cables are much stronger in tension than wood so just a tiny cable will do the job of a 2 x 6 etc.
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