Steel Manufacturing Blog: Keeping it Steel

Rebar Anchors Type I and Type II Connections

Posted on Wed, May 17, 2017 @ 09:31 AM

Weld-on Rebar Anchors can be specified in several types and styles. In each case, there are advantages and disadvantages. What is important, and of utmost concern to the architect and project engineer, is the strength of the connection between the structural steel and the rebar. The strength is designated by the connect type.

Note: Rebar Anchors are also referred to as Weldable Couplers, Weldable Half Couplers, Taper Lock® Weldable Couplers and Bar Lock® Weldable Couplers.

may-blog-fig-1.jpgType I

Type I Rebar connections have a pull out strength of 125% of the yield strength of the rebar. This can be achieved with the basic set screw Rebar Anchor, shown in figure 1. With the set screws turned out, the rebar is inserted to the full depth. The set screws are tightened, which drives the rebar into the serrated edges visible in the lower inside diameter. The pointed tips of the set screws and the 2 rows of serrated ridges form a triangle of contact with the rebar that develops the 125% strength connection required.

The advantage to set screw Rebar Anchors is installation speed and lower cost, compared to Tapered Thread anchors.

A Type II splice can be achieved with a set screw rebar anchor by using the “L” series. These weldable couplers are longer and have 1 or 2 more set screws than the standard length, which increases the connection strength to meet the Type II requirements.

To view the Rebar Anchors and Rebar Couplers catalog, click here.

may-blog-fig-2.jpgType II

Type II Rebar connections have a minimum pull out strength of 160% of the yield strength of the rebar. This is achieved by threading the rebar anchor (Fig. 2, inside diameter shows threading) or extending the length as described above.

The Type II connection can be threaded using 2 different methods: A straight UNC thread or a tapered thread.

Straight Thread: The advantage is consistency. Using standard UNC dimensions, any qualified rebar vendor can thread the rods. The disadvantage of a straight thread is that it is time consuming to install. To achieve the full strength, the rebar must be threaded until it bottoms out. This can require multiple revolutions of the rebar. 

may-blog-fig-3.jpgTapered Thread: The advantage here is installation speed. The taper on the thread is angled more steeply than a pipe thread. The angle is sharp enough that the rebar will insert deep into the coupler before stopping. (Fig. 3) Then, only a few turns will have it bottomed out. While it seems counter intuitive, the connection is as strong as a straight thread because all threads are making full contact. The disadvantages with tapered threads are higher cost than straight threads and inconsistent thread specifications.

“Inconsistent” means each manufacturer uses their own tapered thread dimensions. So, when using tapered thread anchors it is very important that the rebar anchor and threaded rebar both be supplied by the same company. This can create coordination problems between the various trades involved, but it is important with tapered threads to remain consistent.

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Tags: Rebar Anchor, Rebar Coupler

Rebar Anchors and Rebar Couplers:  Who is Covering Them ?

Posted on Thu, Feb 23, 2017 @ 10:17 AM

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.

Click here to see the Weldable Rebar Anchor catalog listings.

D260 Bar Lock Weldable Coupler

Rebar Anchors and Rebar Couplers - Figure 1.jpgIn 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

Rebar Anchors and Rebar Couplers - Figure 2.jpgThe 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

Rebar Anchors and Rebar Couplers - Figure 3.jpgThe 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.

Click here to see the Weldable Rebar Catalog listings.

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.

Click here for full Masonry Anchor Catalog.

Aside from what is shown, any required masonry anchor can be made to order, including break away and low temperature anchors.

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Tags: Rebar Coupler

Four Styles of Weldable Couplers & Anchor

Posted on Fri, Oct 24, 2014 @ 01:13 PM

As engineering standards continue to develop and improve, there seems to be an increasing need for weldable rebar anchors and couplers.   To the average fabricator, these wealth of options represent an opportunity for additional profit but requires some understanding of how each system works.

Here are four types of couplers and studs to consider:

Weldable Coupler - Threaded

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This coupler/anchor is penetration welded to its steel member. This is accomplished by being internally threaded with a tapered thread that perfectly matches the rebar thread.

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Weldable Coupler Set Screws


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For its connection to the steel member, this coupler employs the same penetration weld as the one above. The difference is that it does not require a threaded rebar. Instead, the rebar is inserted and the set screws are tightened to ensure positive anchoring.

Straight Rebar No Threads

Internally Threaded Weld Studs

Internally Threaded Weld Studs

Weld Studs have straight barrels, as in no head, and internal threads. An example of this would be a straight UNC thread with no taper. The Penetration Weld is no longer required. Weld Studs, by design, automatically have a full weld.

Straight UNC Threaded Rebar

Deformed Bar Studs

Deformed Bar Studs

These deformed bars serve the same function as weld studs, and they can be installed with stud welding machinery. However, transportation problems and jobsite safety regulations prohibit this from being done in the fabricating shop. These studs are welded in the field after erection. As a result of the positioning of the anchors, which are typically close to the grade or close to parallel steel surfaces, this becomes a two man process.

Note: All changes must be reviewed and approved by the controlling architects and engineers. We are available to speak to them directly and answer any questions they have.


 

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Tags: Anchor Bolts, Rebar Anchor, Rebar Coupler

Anchor All vs. Epoxy | Pull Out Strength and Hole Diameter

Posted on Thu, Jun 26, 2014 @ 10:41 AM

This blog applies to setting threaded studs, handrail posts, anchor bolts, rebar, etc.

Note: This discussion only covers how hole diameter effects pull out strength. Obviously, the depth of embedment is also a major factor.

When anything is set in concrete, the hole diameter vs. the type of anchoring material used will play a critical role in the eventual pull out strength. As a general rule, you want the pull out strength to be greater than the tensile strength of the stud, anchor bolt, rebar, etc.

For maximum efficiency, the hole diameter should be a function of the anchoring material. The two most common anchors are Epoxy and Grout. Simply, epoxy can work with less clearance than grout. As an example, the epoxy produced by Redhead, EPCON A-7, indicates;

EpoxyRods Diameter 1/4” to 1/2”;
Drill hole 1/16” larger than rod diameter

Rods Diameter 5/8” to 1-1/4”;
Drill hole 1/8” larger than rod diameter

Any larger than that and the epoxy will not function as intended.

Portland Cement Based Non-Shrink Grout

On the other hand, cementitious non-shrink grout requires at least 1/2” clearance around all sides to develop its full compressive strength. So for a 1-1/4 diameter schedule 40 pipe, with an O.D. of 1.66", the hole should be no less than 2.66”. In this case, the erector would most likely use the core drill next size up, which would be 3” diameter.

Anchor allConverse to the epoxy requirements, when using Anchor All, there is no limit on how much larger the hole can be, as long as it provides at least the required 1/2” clearance in every direction.

This is also true when setting square posts. As shown in the square post drawing below, a 1-1/4” square tube being set in a 3” diameter hole leaves only 0.44” clearance at each corner. If installed as shown cracking and/or premature failure could occur. Also, simple calculations would show anyone examining this installation proper procedure was not followed. This could result in charge-backs or retainage being withheld.

This, along with greater depth range, is why the EZ Sleeve is available in a larger 4” x 12” clearance for square postsmodel. To learn more about the EZ Sleeves we carry, click below to view the options:

 

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The other important factor to consider when determining the hole diameter is cost of the epoxy. By comparison, Epoxies can cost 20 to 25 times what Anchor All Cement based non-shrink grout costs. To learn more about this, click below to view our hydraulic cement and non-shrink grout products.

 

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Tags: EZ Sleeve, Anchor Bolts, Rebar Anchor, Rebar Coupler, Non-Shrink Grout, Hydraulic Cement

Rebar Anchors / Couplers and The Structural Steel Fabricator

Posted on Tue, Jun 17, 2014 @ 02:47 PM

Things are changing a bit for both structural and miscellaneous steel fabricators. In the past, they have mostly stayed away from anything to do with concrete and the masonry side of the business, including rebar. Their interaction was often limited to welding masonry anchors onto columns and beams. This applied to items such as the wire tie, the Hohmann & Barnard Gripstay or the slotted channel.

rebar couplerThat changes somewhat, as rebar anchors, also known as rebar couplers, are being designed into projects more often. In short, a rebar anchor connects the rebar to a column, beam, relieving angle or any steel member with a strong, positive connection. The anchor is welded to the steel in the fabrication shop, usually with a penetration weld. Later, once the erection is complete the rebar is locked into the anchor. Typically, this step is still done by the mason.

If the anchor / coupler is intended to be welded to steel it should come with a beveled edge to allow for a penetration weld. (See fig. 1)

In the field, the rebar connects to the anchor / coupler in one of three ways. The rebar connects to the anchor in a few ways; the set screws as shown in fig. 1, with a tapered thread, as in fig. 2, or rebar anchorwith straight threads. The fabricator should note several things about the thread systems during the process.

The tapered thread is not a pipe thread, which has a gentle taper designed to tighten slowly and form a leak proof fitting. Rebar tapered thread systems are designed for steel and concrete construction and have a more pronounced taper. This is done this way for installation speed. Often, when the rebar is threaded into the anchor, it is long and heavy. Tapering the thread enables the installer to insert it as far as possible before turning. Then, with a few twists, the tapered thread tightens with all threads making full contact.

rebar couplerFig. 3 shows the Dayton Superior item D106 straight thread or D360 tapered thread.

In the case of the D106 straight thread anchor, the rebar should have an upset thread. “Upset” means the thread is actually larger in diameter than the rebar itself. This is achieved by heating and expanding the rebar end and then threading. Fig. 4.

Also, VERY IMPORTANT. Tapered Rebar Anchors do not have a standard such as UNC. Each manufacturer threads with the intention their product will be used for both the anchor and the rebar. We know of four main manufacturers of the rebar anchoranchors / couplers. Dayton Superior, Lenton, Bar Splice and Ancon. Located in the U.K., Ancon does not appear on U.S. projects often. The shop drawings we see most often specify Dayton Superior or Lenton. The fabricator should use the type specified to assure the tapered thread insert purchased by the rebar contractor will thread properly into the coupler and lock with sufficient strength.  

While this should not affect the D106 straight thread system, it is nonetheless recommended the steel fabricator adhere to the system called out in the plans.

 

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Tags: Masonry Anchors, Rebar Anchor, Rebar Coupler