There are several ways rebar anchors can be portioned out in a construction job. They can be part of the steel fabricating package and that is all, they can be part of the steel package and include the first length of rebar, or they can be left entirely for the rebar contractor. We see these divisions all the time with specific product lines, such as Teflon® or Fluorogold® Slide Bearings, Elastomeric Bearings, Steel Wedges, etc. They are part of a project but it is not clearly noted who is responsible for them.
Rebar Anchors/Rebar Couplers are being designed into structures more frequently than in the past, and Architects and Engineers are gaining an understanding of how to plan for them with minimal difficulty. Logically, the simplest way to apportion Rebar Anchors is to have the steel fabricator weld the anchor to the column or beam in their shop. The rebar fabricator/installer can take it from there, and hence, every trade stays within its own specialty. In this case, it is important the designers, the fabricators and installers all understand what variations may be involved.
D260 Bar Lock Weldable Coupler
In terms of ease of use, the simplest Rebar Anchor is the D260 Bar Lock® Weldable Coupler. See Fig. 1. Notice on the inside diameter of the open end, there is a serrated ridge. There are actually two separate ridges (the second is not visible from this angle) and they run the length of the barrel. The rebar is inserted to full depth and the set screws are tightened, until the heads snap off.
The erector need only be sure the rebar is in all the way, and all three set screws are making contact with the rebar. The D260 series couplers will develop a type 1 splice with grade 60 rebar. If necessary, a type 2 splice can be achieved by using a D260L series coupler. The advantage with the D260 or D260L series is any rebar of the correct diameter will fit without any extra fabricating, threading or machining.
D106 Weldable Coupler – Straight Thread
The D106 Weldable Rebar Coupler uses a straight thread for its anchoring system. The connecting rebar can be threaded to UNC bolt thread specifications. With proper thread tolerances, D106 Weldable Coupler can provide a type 2 splice. It should be noted that rebar employing straight thread often calls for an upset thread diameter, meaning the body of the rebar is expanded and the thread pitch is actually a larger than the diameter of the rebar.
Another issue to consider regarding straight thread rebar is the time it takes to fully thread. For example, a #5 rebar may have an upset thread at 3/4-10 pitch. That means for every inch the rebar goes into the coupler, it needs to be rotated 10 times.
D360 Weldable Coupler – Tapered Thread
The D360 Weldable Rebar Coupler uses a tapered thread to connect with the rebar. The most important factor to understand is that the thread taper is unique to the manufacturer. They do not conform to a standard, such as UNC (Straight) or NPT (National Pipe Thread, which is the standard taper).
For this reason, it is important that the fabricator and rebar contractor know which type of rebar coupler is being used and be sure that the threading has been done by that same company.
This goes back to the original question. If the rebar contractor is responsible for all parts of the rebar anchoring system, coordination of the parts is definitely easier. But actually, welding in the field is much more difficult and depending on the placement of rebar anchor on the column, it may not be feasible to get a full 360° penetration weld.
Welding the rebar anchors to the columns in the fabrication shop is more efficient and allows for greater accuracy and quality. From there, the steel fabricator may be asked to provide the first section or rebar with the mated thread system. Often, this not a full-length piece of rebar, but enough to extend into the rebar pattern where couplers allow it to connect to the system.
Weldable Rebar Anchors are just one of the Masonry Anchors that The Steel Supply Company offers to the Structural and Miscellaneous Steel Fabricator. To see the full catalog of Rod Anchors, Wire Ties, Slotted Channel, Slotted Channel and Gripstay Inserts, Wedge Inserts and Askew Head Bolts, click the link below.
Aside from what is shown, any required masonry anchor can be made to order, including break away and low temperature anchors.