JM Vassallo Vibro Steel introduces Dextra Rebar Couplers

Aiming to broaden the range of construction technologies in Malta, JM Vassallo Vibro Steel Ltd. (JMV) is proud to announce the addition of Dextra Couplers to their portfolio.

This initiative reflects JMV’s dedication to propelling construction technologies forward and to enhancing its range of construction products and building solutions.

Established in 1969, JMV has consistently been at the forefront of setting industry benchmarks. Operating from an expansive 20,000 sqm. facility in Zebbug, which houses its steel processing plant, JMV’s adoption of Dextra Couplers represents a significant advancement, promising enhanced efficiency and quality in the Maltese construction industry.

Dextra Group, a global frontrunner in rebar couplers and building solutions, operates through an extensive network of over 80 distributors, maintaining 12 offices and 3 manufacturing facilities worldwide. Their diverse range of couplers includes solutions for cast-in-situ applications, precast elements, and repair operations.

The advantages of employing couplers are primarily twofold: in design and constructability. From a design standpoint, couplers facilitate superior mechanical performance and address technical challenges like rebar congestion by eliminating the need for rebar laps.

In terms of constructability, they offer cost reductions for connecting larger diameter rebars, reduce protruding bars, and accelerate the construction process.

Dextra sets itself apart with its unique bar break system, utilising a cold forging process alongside a parallel thread system. The premise here is simple: during a tensile test, the rebar breaks outside of the coupler, proving that the coupler connection is stronger than the bar itself.

during a tensile test, the rebar breaks outside of the coupler, proving that the coupler connection is stronger than the bar itself

The integrity of a coupler system is critical, especially in scenarios where failure under stress could lead to suboptimal tensile capacity of the rebar. By increasing the cross-sectional area at the threading point, Dextra’s system ensures a full performance splice and guarantees a bar break splice that preserves the rebar’s ductility.

The parallel thread design not only enhances productivity but also simplifies quality control, easily verified using go-no-go gauges. This system also boasts symmetrically profiled threads, ensuring equal tensile and compression performance. The on-site tightening process is straightforward, requiring no specialised labour or calibrated torque wrench, unlike taper-thread systems.

Conventional taper-thread systems cannot guarantee a bar break. These systems often reduce the rebar’s cross-sectional area in the threaded region, thus diminishing its ductility and causing the total elongation at maximum force (Agt) to drop significantly below the 7.5% characteristic of grade B500C rebar. Additionally, taper threads suffer from lower productivity and more challenging quality control.

In seismic applications, seismic waves can affect the bond between rebar and concrete, compromising lap splice load transfer and structural load-bearing capacity.

The parallel thread design not only enhances productivity but also simplifies quality control

Mechanical rebar couplers, independent of rebar-concrete bonding, are considered safer for seismic conditions than lap splicing. Conventional lap splicing often leads to reinforcement congestion and over-reinforced, brittle concrete behaviour due to stress concentration, diminishing elements’ deformation capacity.

Rebar ductility, crucial in seismic design, is measured by elongation at maximum force. For rebar couplers, ductility requirements are lower than the “bar break” level, necessitating couplers to ensure no reduction in rebar capacity through cross-sectional loss. Thus, “bar break” rebar coupler systems surpass the ultimate tensile strength of connected rebar, and ensure that failure occurs away from the coupler, offer strength and ductility advantages, preserving the connecting rebar’s ductility.

Dextra couplers are backed by a comprehensive traceability system, tracking material origin and production batch references, and are produced under a stringent ISO 9001 certified quality assurance plan.

Headed Bars

Headed bars offer a further solution to threading rebar by offering a simple and effective alternative to hooks and long development length. A compact disc is mounted onto the bar end.

Headed Bars contribute to reducing rebar congestion in heavily reinforced areas, which ultimately eases the compaction process and results in better concrete quality in key areas of the structure

The assembly of the rebar and the anchor provides an anchorage superior to straight or bent rebar. Headed Bars contribute to reducing rebar congestion in heavily reinforced area, which ultimately eases the compaction process and results in better concrete quality in key areas of the structure.

Groutec Couplers:
Enhancing Precast Construction

In addition to the Fortec and other coupler systems, Dextra also offers Groutec Couplers, an innovative solution specifically designed for precast construction applications. They are designed for the connection of precast concrete elements and comply with Eurocode 2, ISO15835 code requirements.

Each Groutec sleeve features a threaded end for the connection to reinforcement bars at the precast factory and a wide body allowing for more misalignment tolerance for the connection of two precast elements at site.

Groutec is compatible with ribbed or deformed reinforcing bars in diameters from Ø12 to 40 mm and can connect bars prepared with Dextra thread systems.

At the construction site, connection is made in a few seconds by injecting/pouring non-shrink grout into the cavity, both horizontally and vertically.

JM Vassallo Vibro Blocks Ltd
Vibro Complex, Mdina Road,
Haz-Zebbug ZBG 9019, Malta
Tel.: (+356) 2146 7421
EMail: sales@jmvibro.com
: https://www.facebook.com/JMVibro