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Dextra’s Quarterly Newsletter: Connection #3

Dextra has developed the ultimate alternative to removable ground anchors

Hint: it doesn’t need to be removed

Temporary ground anchors are used in numerous applications including slope stabilization and excavations. Contractors usually install steel ground anchors, and then remove them once they become obsolete: a double burden.

Dextra has developed a range of innovative post-tensioned anchors: ASTEC Active Anchor (AAA)

  • Cuttable tendons made of GFRP material, corrosion resistant and possessing with tension performance to steel. More importantly in this case, it has the advantage of being easily crushed by tunnel or piles boring machines. Therefore, it doesn’t need to be removed from the ground.
  • Conventional steel PT strands compatible with any standard tensioning device (hydraulic jack), connected to GFRP tendons thanks to a proprietary connector. Assembly, installation & tensioning remains the same as for steel ground anchors.

Since mid-2014, Dextra delivered thousands of ASTEC Active Anchors in the Middle-East, both using CFRP & GFRP material. Many of them have been used in projects related to Doha Metro in Qatar, combining up to 10 tendons for an ultimate capacity of 250 tons. The FRP anchors have been selected as they allow the tunnel boring machine to cut through without generating any issue of encroachment on neighboring plots.

Post-Tensioning Bars for temporary and permanent applications

Dextra offer ranges from Fully Threaded Bars to Smooth Bars and full accessory systems

Dextra supplies a complete range of Pre-Stressing and Post-Tensioning high performance bars. Dextra product range includes fully threaded bars (3 grades available) and smooth bars with threaded ends (also available in 3 grades) and are supplied with plates and nuts.

PT Bars are usually used for temporary applications like heavy lifting, fixing, pile testing and permanent application such as anchoring or seismic protection.

For ground applications, Dextra can supply its bars with single or double corrosion protection systems as per BS 8081 and EN 1537.

For the post-tensioning of elevated precast segments (roads or metro), Dextra also provides full shear key and hold down bar systems with anti-corrosion accessories.For more information, please download our Post-Tensioning Bar Systems brochure.

Rebar Couplers: New Splice Fixing Box accessory

The Splice Fixing Box improves rebar alignment and create a convenient key in concrete

Dextra released a new accessory to support its coupler product range for both in situ casting and precast applications.

The Splice Fixing Box is composed of an aluminium box with 15 holes, each of them partially punched in 4 different diameters. The box also comes with threaded plastic plugs that fit the desired rebar coupler size, available for rebar size 12mm to 25mm.

The Splice Fixing Box creates a key in concrete and allows to perfectly align and space couplers in critical areas.

Large Soft Eyes installed. Tunneling about to start in Hong Kong!

Dextra Soft Eyes will soon be crossed by the world’s largest boring machine

25 March 2015 sees the inauguration ceremony of the future 5 km long sub-sea tunnel in Hong Kong linking Tuen Mun to Chek Lap Kok. This significant project is led by Dragages – Bouygues Joint Venture and consulting firm AECOM.

The world’s largest Tunnel Boring Machine, 17.6 m in diameter, has been assembled and positioned to start excavating through the enormous GFRP softeyes in the diaphragm walls supplied by Dextra.

Dextra also supplied Rolltec couplers used in various applications, including the thrust frames plinths as seen in the lower zoomed part of the picture.

Morocco Tanger Med 2: Couplers on a caisson port

More than 180,000 couplers were used on the expansion of one of the largest African ports

Tanger Med 2 is a port expansion project directed by Bouygues and Saipem near Tangier, Morocco. It features a new port area protected by 105 caissons, each of them including more than 6 tons of reinforced concrete. For this project Dextra supplied 180,000 Rolltec couplers supported by a couple of on-site Rolltec rebar preparation equipment. Couplers were used in various areas of the caisson, including vertical inside walls and horizontal slabs on the top of the structure.

Main benefits of coupler applications:

1. Temporary openings for ease of moving material and people during the different steps of the construction.

2. Use of slip form for fast cycle caisson building.

For more details, please download our full case study.

Nhat Tan Bridge inaugurated in Hanoi, Vietnam

Dextra supplied Bartec couplers on the longest cable-stayed bridge in Vietnam

This 4th of January, the Ministry of Transport of Vietnam inaugurated in Hanoi the Nhat Tan Bridge, officially opening the project to the public. The total length of the project is 8.9 km, including the impressive 3.75 km cable-stayed Nhat Tan Bridge spanning over the Hong (Red) River. The bridge is the new gateway to Hanoi when travelling from the International Airport and neighboring regions.

The Nhat Tan Bridge has been under construction for almost five years. Dextra Manufacturing supplied for this project more than 120,000 Bartec rebar couplers used in the pylons of the bridge, as well as Post-Tensioning Bars and their accessories.

Dextra is excited to be part of this landmark project which plays an important part in the modernization of the infrastructure of the Vietnamese capital.

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