What Is A Coupler Used For In Construction?

What Is A Coupler Used For In Construction
Regional Sales Manager at Dextra Group – Published Jan 4, 2020 1. Introduction One common aspect of reinforced concrete construction is the need to splice reinforcing bars, whether it is to provide continuous reinforcement over a long expanse, to extend a reinforcing bar beyond where it currently ends, or to replace a section of in-place bar that has sustained damage. As defined in ACI 116-05; a mechanical rebar splice is “the complete assembly of an end-bearing sleeve, a coupler, or a coupling sleeve, and possibly additional intervening material or other components to effect a connection of reinforcing bars”, According to ASTM A1034; a coupler is a threaded device for joining reinforcing bars for the purpose of providing transfer of either axial compression or axial tension or both from one bar to the other. 2. Main Building Codes Requirements

ECP 203-07 (Section 7-3-2-2) “Failure load of the mechanical splices should exceed 125% of the rebar yield load. Permanent slippage in the mechanical splice should be less than or equal 0.1 mm at the working load.” ACI 318-08 (Section 12.14.3.2) “A full mechanical splice shall develop in tension or compression, at least 1.25 fy of the spliced bar (125% of specified yield strength of the spliced bar).” ACI 318-08 (Section 21.1.6.1) – Type 1 “Type 1 mechanical splices shall conform to 12.14.3.2.” ACI 318-08 (Section 21.1.6.1-b) – Type 2: Seismic “Type 2 mechanical splices shall conform to 12.14.3.2 and shall develop the specified tensile strength of the spliced bar.” BS 8110 (Section 3.12.8.16.2) “The tensile strength of the coupled bar should exceed 287.5 N/mm² for grade 250, 525 N/mm² for grade 500 A and 540 N/mm² for grade 500 B. The permanent elongation after loading to 0.6 fy should not exceed 0.1 mm.”

3. About Dextra Rebar Couplers Established in 1983 by French expatriate entrepreneurs, Dextra Group has developed over a long history, during which it encouraged those with an entrepreneurial spirit and constantly strived towards innovation and growth, leading to diversification. Dextra’s three main activities are manufacturing, trading and freight forwarding, all within the construction and industrial sectors. Dextra couplers are very versatile in their use and allow important productivity gains in the construction process. They create a strong point in the rebar structure, maintaining the ductility of the reinforcement. Dextra couplers also allow to significantly reduce the tonnage of rebar used by avoiding the traditional bar overlapping.

Dextra Bartec®, Fortec® and Griptec® are full tensile splices systems, which means that under tensile loading, the failure occurs in the reinforcing bar, away from the coupler. Avoiding a failure at the connection means that the ductility and the ultimate performance of the reinforcement as a whole are not affected by the mechanical splices.

Bar break capability is especially recommended for sensitive applications such as nuclear reactors and demanding environments such as seismic areas.4. Typical Applications Well known in the construction industry, Dextra rebar splicing solutions allow to swiftly connect reinforcement bars to fit different rebar grades and sizes according to the various standards across the world.

Rebar continuity for cast-in place concrete Solutions allowing fast, high-performance and reliable rebar connections thanks to their parallel-thread system. Prior preparation of the rebar is done thanks to a highly productive Dextra equipment. Typical applications such as Piles, Pile caps, dwalls, walls, slabs, beams, columns and temporary openings. Precast connections Solutions which allow the connection of precast elements together without the needs of wet in situ joints. Typical applications such as columns, beams, wall panels and pipe racks. Repair and retrofit Solutions which do not require the bars to be prepared, can be operated with light tools and require a minimal bar length. Typical applications such as piles and barettes.

4.1. Rebar Continuity for Cast-in Place Concrete 4.1.1. Griptec® Dextra Griptec® is a full performance (tension / compression / cyclic / fatigue) rebar splicing system designed to comply with the world’s most stringent project specifications. Griptec® is the preferred system for nuclear reactor buildings worldwide.

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A standard Griptec® connection is made from the connection of one male and one female sleeve, both are extruded onto the rebar. Additional intermediate connectors allow for Positional/Bridging applications.Solution supported by a single, safe, clean, smart and fully automated rebar preparation equipment with built-in reporting and alert features.Systematic proof load tensile testing of each and every connection to the rebar.Unrivalled splicing system performance: in tension, compression and fatigue, thanks to the unique design of the product and associated processing equipment.Compact design for congested applications.Joints verified by visual inspection with no requirement to induce a specific torque value.No reduction of cross-section area of the bar.

4.1.2. Bartec® / Fortec® Dextra Bartec® (Fortec® is the equivalent solution for European markets) is a full performance (tension / compression / cyclic / fatigue) rebar splicing system designed for the connection of concrete reinforcing bars from Ø12 to 50mm (ASTM #4 to #18).

A standard connection is made of parallel-thread rebar coupler and two bars which end have previously been enlarged before being threaded: thus the cross section of the bar isn’t reduced.Solution supported by 3 high-productivity machines which prepare each bar in sequence: clean square cut, enlarging of the bar end by cold forging and then threading.Threads on the rebar can be extended from a half-coupler to a full-coupler length, allowing to use the very same standard coupler for positional applications (no need to rotate bars to perform the connection).

Simplify your inventory: A single standard coupler for most applications.No reduction of cross-section area of the bar, making your coupler connection a strong point of the structure.Working in tension/compression thanks to its parallel-thread technology.Joints verified by visual inspection with no requirement to induce a specific torque value.

4.1.3. Rolltec® Dextra Rolltec® is a rolled-parallel threaded mechanical splicing system designed for the connection of concrete reinforcing bars from Ø12 to 50 mm (ASTM #4 to #18). Rolltec® solution is supported by a single rebar preparation equipment, which is operated by a single operator. Rolltec® couplers comply with ACI 318, IBC 2006, BS 8110, Eurocode 2, DIN 1045, CalTrans, ASME Sec III Div 2.

A standard Rolltec® connection is made of parallel-thread rebar coupler and two bars where threads have previously been formed by cold-rolling.Rolltec® bar preparation is made in sequence by a highly productive equipment which peels and form threads in sequence in a single operation. Only one man is needed to operate the machine!Rolltec® threads on the rebar can be extended from a half-coupler to a full-coupler length, allowing to use the very same coupler for positional applications (no need to rotate bars to perform the connection).Practical and simple alternative to laps.Shorten construction cycle times.Parallel-thread technology: No torque wrenching at a specific value required.Precast and Headed Bars ready: take advantage of Groutec threads to connect Groutec precast coupler or Headed Bar anchorages.

4.1.4. Headed Bars Dextra Headed Bars are a simple and effective alternative to hooks and long development length. A compact disc is mounted onto the reinforcement bar end. The assembly of the rebar and the anchor provides an anchorage superior to long straight or bent reinforcement bars, while being simpler and faster to install.

Made of an anchor plate that is screwed onto the end of the reinforcement bar.Headed Bars are a convenient alternative to hooks in congested areas.Anchors are available into two standard sizes to provide a net bearing area 4 or 9 times equal to the cross section area of the bar.Requires the same bar end preparation as Dextra coupler systems and compatible with Bartec®, Fortec®, Griptec® and Rolltec® threads.As main reinforcement; less congestion, ease of installation. Threaded heads can be fitted on site after rebar installation, no more risk of rebar embrittlement due to bar bending, require shorter anchorage (development) length, more faithful realization of strut-and-tie modeling, and better anchorage effectiveness (lower bearing stress and less slip) especially on large diameter barsAs transverse reinforcement; shear reinforcement in slabs and footings, cross ties in walls, columns and diaphragm walls, faster installation time, no more site bending of double-headed 135° or 180° hooks, and allow use of larger bars, therefore decreasing the quantity of links.

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4.2. Precast Connections 4.2.1. Groutec Dextra Groutec is a mechanical splicing designed for the connection of precast elements. Each Groutec sleeve features a threaded end (used for the connection to reinforcement at the precast factory) and a wide cavity to perform a grout connection at site. Groutec is designed and manufactured in compliance with Eurocode 2, BS 8110, ACI 318, IBC, AASHTO.

Available in two versions (Slim “S” and Large tolerance “L”) for fit your design and manufacturing process.Compatible with ribbed or deformed reinforcing bars in diameters from Ø12 to 40 mm, in grades up to 550 MPa (80 ksi).Groutec can connect bars prepared with any of Dextra thread systems: Rolltec®, Bartec®, Fortec® and Griptec®.At the construction site, connection is made in a few seconds by injecting/pouring non-shrink grout into the cavity.Horizontal or vertical connections, in upper or lower element, Groutec can do it all!Engineered, tested and compatible with major non-shrink grout brands easily available on the market: Sika, Parex-Davco, Fosroc, BASF and Pozament. Reduce overall cost and simplify sourcing.At the precast factory, fast and precise installation thanks to Groutec threaded end. Take advantage of the full range of accessories available to simplify your pre-casting process.At site, large axial misalignment is tolerated thanks to Groutec wide cavity.Fast: Inject or poor grout into the cavity in less than 5 seconds. Bracing can be removed after 3 days.

4.3. Repair and Retrofit 4.3.1. Unitec® Dextra Unitec® is a bolted splicing system designed for the connection of two rebar which haven’t been previously prepared (no thread). Each Unitec® coupler features a long hollow body which will bond with rebar. Several screws will lock both bar ends and complete the connection. Unitec® is designed to be operated with a standard impact/pneumatic wrench.

Unitec® is a shear-bolt coupling system for the connection of concrete reinforcement bars from Ø12 to 50 mm (ASTM #4 to #18).No specific torque measurement required. Simply engage the screws until the heads shear off, notifying that the required torque has been applied.Available off the shelf and close to you thanks to our network of distributors.Positional splicing with butt-to-butt rebar connection possible, please refer to our Installation Instructions.Only light equipment is required, making Unitec® an ideal solution for remote locations.No rebar preparation whatsoever, no welding, no chemical products and no grouting.Minimal rebar length required. Ideal for coordination issues when rebar protruding length from foundation piles is insufficient to perform standard overlap.

4.3.2. RepairGrip Dextra RepairGrip system is a portable system designed to splice bars in-situ. It is a simple and proven method to splice bars that did not have their end shop-prepared. The RepairGrip sleeve is swaged onto the bar ends by a hydraulic tool powered by a separate power unit.

RepairGrip system can splice bars from diameter Ø12mm to 40mm.RepairGrip splices put rebar ends butt-to-butt, making the solution suitable for tension and compression applications.No rebar preparation required.Minimal rebar length required. Ideal for coordination issues when rebar protruding length from foundation piles is insufficient to perform standard overlap.Supported by a Dextra-supplied equipment.

5. Dextra Engineering At every moment of your customer journey, Dextra teams dedicate themselves to the making of smart construction solutions that allow customers to reach higher productivity and safety level on their construction sites. For consultants and designers looking forward to integrate Dextra solutions in their construction drawings, Dextra’s BIM team offers software tools for Tekla Structures, Revit 2017 and AutoCAD. 6. References

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Egyptian Housing and Building National Research Center – Egyptian Code Standing Committee, Egyptian Code for Design and Construction of Concrete Structures (ECP 203-07).American Concrete Institute – ACI Committee 318, Building Code Requirements for Structural Concrete (ACI 318-08) and Commentary (ACI 318R-08).British Sector Board for Building and Civil Engineering – Technical Committee B/525, British Standard for the Design and Construction of Reinforced and Pre-stressed Concrete Structures (BS 8110).Concrete Reinforcing Steel Institute – CRSI, “Frequently Asked Questions (FAQ) About Mechanical Splices,” CRSI Technical Note ETN-M-4-14.Concrete Reinforcing Steel Institute – CRSI, “Tensile Strength of Lap Splices in Reinforced Concrete Members,” CRSI Research Note RN 2011-1.Dextra construction activity brochure – September 2018 – PS+SIMechanical Rebar Splices – Jan 2019 – PS + SIwww.dextragroup.com

For any further questions, please feel free to contact me. Kevin Hany | +2012 2450 2771 | [email protected] | linkedin.com/in/kevinhany

What are the mechanical couplers for rebar?

The component that used to joint the reinforcement is called the mechanical couplers. They are sometimes called as rebar couplers. Why do we need mechanical couplers? It provides more benefits to construction in different terms. Poor quality joints may lead to structural failures. Mainly there are two types of couplers for rebar.

How mechanical couplers are used in construction industry?

Mechanical couplers are widely used in the present construction industry to joint two reinforcement bars together. The lapping of reinforcement is very difficult and time-consuming. Further, some costs also can be saved with mechanical couplers. In addition, it is a saving of materials and very useful in the areas where the reinforcement is congested.

What is a bar lock coupler?

What Is A Coupler Used For In Construction Bar Lock couplers are effective when used as a positional coupler when the rebar is fixed in place or when the rebar is free to rotate. The couplers utilize lock-shear bolts and serrated grip rails too mechanically splice the rebar. The serrated grip rails are embedded in the rebar as the lock-shear bolts are tightened.

  1. The heads of the lock-shear bolts are designed to shear off at a prescribed torque to ensure proper installation.
  2. Features: Rebar sizes #4 (13mm) through #18 (57mm) Available in plain, epoxy coated or galvanized finish Quick and easy installation No bar end preparation Installation at the job site Used in tension, compression and seismic applications D250 and D250XL Bar-Lock Couplers are available in a wide variety of sizes in plain, galvanized, and epoxy-coated finishes.

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How many types of couplers are there in structural concrete?

Different Types of Mechanical Couplers – Mainly there are two types of couplers for rebar.

  1. Tension Couplers
  2. Compression Couplers

Mainly the couplers are used to carry the tensile force. However, they are using to carry the compressive forces. Further, most of the time, couplers are tested for tension. The following figure indicates the different types of couplers available in the construction industry. Figure from the standard method of detailing structural concrete. There are seven types of couplers that can be used to connect the reinforcements. Each of those types can be applied in the construction based on the application and as per the need of the construction. These couplers can be used for beams, slabs, columns, shear links, etc. The application shall be as approved by the engineer at the site or as per the recommendation of the structural engineer. There are different standards/guidelines such as Report by ACI committee 439, BS 8597:2015, etc can be used for the design and construction.