Post Tensioning - Benefits
Post Tensioning Concrete enables the Dunne Group to utilise the entire range of allowable stresses across the section depth, creating a strong , slender and efficient element. Post Tensioning is a technique of pre-loading the concrete in a manner which control stresses and deflections that are induced by the self weight and applied loads whilst the structure is in service.
In Post Tensioned structures, high tensile steel strands are placed in the concrete at profiles as required to balance the dead and imposed loads. When the correct concrete transfer strength has been reached the strands are stressed to the required force and anchored at the slab edge.
Through ConForce, Dunnes have a group company available to carry out design/supply/install packages for post tensioning work on concrete frames. This brings an “integrated team” approach for clients supplying a complete post tensioned concrete frame package and reducing interfaces. The most common application of post tensioning at present is in suspended slabs in buildings. Many contractors including Dunnes are using this as a standard construction method where the benefits (as listed below) have been clearly demonstrated.
Dunnes are able to offer, using ConForce, the MK4 Post Tensioning system. This is a comprehensive range of anchorages for bonded and unbonded tendons with a proven track record in the UK and many other countries. The MK4 PT System has European Technical Approval in accordance with ETAG 013, “Post Tensioning Kits for Prestresssing of structures”.
Post Tensioning is also used in Civil Engineering structures for example bridges and circular tanks . Here the Multistrand system is used where tendons can comprise up to 37 strands, to provide the higher prestress forces used in these structures. These tendons can also be used in large transfer beams in buildings.
The technical knowledge gained by the staff at Dunnes and ConForce is available to provide clients with fast, economic and innovative solutions for all types of structures using the many post tensioning systems and techniques that are available.
Advantages of Post Tensioning Concrete
- Reduction in depth of slab (common depth/span ratios of 1:40)
- Reduction of depth of beams (common depth/span ratio of 1:20)
- Controlled cracking – beneficial in car parks.
- Very economic and structurally efficient over 6m spans
- Flexibility in planning & design
- Deflection can be controlled and is reduced compared to r.c.
- Smaller quantities of reinforcement required
- A prestressed structure is ‘pre-tested’ since a significant load is applied during post tensioning..
For further technical information please visit Conforce at www.conforce.co.uk