New Steel Fabrication Opportunities: Rebar Couplers
Rebar coupling provides steel fabricators with exciting new opportunities; however, the advantages and disadvantages of each type of rebar coupler must be considered.
As advancements in engineering and architecture continue, steel fabricators are increasingly required to find new opportunities to expand their work in rebar coupling. Rebar acts as a structural bearing in concrete. To provide maximum strength, it requires connection to a steel member. In recent years, the options for this connection have moved forward, creating greater opportunities for steel fabricators, but also additional complications.
Frequently, rebar anchors will be specified on drawings and show a manufacturer’s part number called out. However, if a specific product is not indicated, or left generic, choosing the correct coupler is paramount to the success of a steel fabricator in this process. Each rebar coupler has its own advantages that should be considered.
The first thing to consider with regards to rebar coupling is the pull out strength required. There are two standard grades of rebar couplers in terms of pull out strength: Type 1 and Type 2.
A Type 1 rebar coupler has a pull out strength that measures at 125% the yield strength of the rebar, while a Type 2 rebar coupler has a pull out strength that measures at 160% the yield strength of the rebar.
For Type 1 rebar couplers, The Steel Supply Company recommends using Dayton’s D260 Bar Lock® Weldable Coupler. This coupler has two serrated ridges at the bottom of its barrel. These ridges run the length of the barrel and act to secure the rebar in place. Rebar is inserted as deeply as possible into the coupler, and then it is tightened into place by the set screws located at the top of the coupler, opposite the serrated ridge. These set screws are tightened until their heads snap off.
The benefits of the D260 Bar Lock® Weldable Coupler are easily recognized. It provides a seamless installation that can be undertaken on the job site, and no fabrication or rebar preparation is required.
For Type 2 rebar couplers, threading is required, and there are two types of threading styles that are used: tapered and straight.
Couplers with a tapered thread typically have a much more pronounced taper angle than what would normally be seen in something like a pipe taper. The purpose of this pronouncement is to allow for faster installation speed. The threaded rebar is inserted into the coupler past the outside most threads, and then turned once it makes contact with the coupler’s inner threads. This enables the rebar to be installed into the coupler with a minimal amount of turning, while also ensuring that it is connected entirely with the coupler’s threads.
For steel fabricators requiring a tapered thread, The Steel Supply Company recommends using Dayton’s D360 Weldable Rebar Coupler, but it’s to important note that taper threaded couplers do not have a UNC specification by which they are measured. The coupler is threaded by the manufacturer with the intention that the fabricator will use their coupler and their rebar.
The taper threaded coupler provides advantages in both size and installation speed. Its compact measurements make it ideal for confined spaces, and its tapered threading design minimize installation speed, as described above.
For straight threaded rebar couplers, The Steel Supply Company carries Dayton’s D106 Weldable Rebar Coupler. Its major advantage is its compliance with UNC bolt thread specifications. Unlike couplers with a tapered thread, steel fabricators can use this coupler with rebar supplied by a different manufacturer.
However, straight threaded rebar couplers typically require additional preparation of the rebar. Most require the rebar to have an upset thread diameter, which means that the head of the rebar is expanded and its thread pitch will actually be larger than the rebar’s normal diameter. Straight thread rebar couplers also require a greater amount of installation time for the rebar, since it must be turned once making contact with the first thread.
Lastly, aside from connecting rebar with its steel member, steel fabricators will also have to consider the case in which a piece of rebar needs to be connected to another. Rebar is generally never manufactured longer than 20’, so a connection between rebar will be required on projects that are longer. Rebar is manufactured in specific lengths and most often requires connecting, or “splicing” to another length of rebar. For this case, The Steel Supply Company carries Dayton’s D250 Coupler, which uses the same bar lock system described for the D260 Bar Lock® Weldable Coupler.
To connect with a steel member, all rebar anchors come with a beveled edge, which allows for a full penetration weld.