Post-tensioning

Post-tensioning is a technique designed to reduce the slab thickness for reinforced concrete. Post-tensioning tendons, which are prestressing steel cables inside a galvaniused duct, are positioned during slab construction before the concrete is placed. Afterwards, once the concrete has gained strength but before the service loads are applied, the cables are stressed to pre-load the concrete.


Flat Slab Post Tensioning
The latest version of the Structural Systems CMF flat slab post tensioning system is ETAG compliant and is ideal for low or high rise residential or commercial buildings, transfer slabs and industrial floors (slab on grade). The system requires simple formwork and saves significantly on both the slab depth and the traditional reinforcement requirement, whilst increasing the spans between columns and allowing better control of the deflections within the slab.

Multi Strand Post Tensioning
Structural Systems has two distinct systems that it uses for predominantly civil structures including bridges, silos, tanks and off-shore structures. These multi-strand applications require either the BBR Cona Multi or the BBR VT Cona CMI. The BBR Cona Multi –M1 (M3 for cryogenic applications) consists of up to 61 No. 12.7mm/12.9mm strands or 91 No. 15.2mm/15.7mm strands. The BBR VT Cona CMI is a revolutionary state of the art bonded post tensioning system available with 4-61 strands for 15.2mm or 15.7mm strand. The system is ETAG approved.

Multi Wire Post Tensioning
The BBR SSL Multi-Wire System is more compact than the multi-strand system and is often preferred for coupled cables in incrementally launched bridges and is ideally suited where the cables are to be prefabricated and where re-stressing or de-stressing is required. The multi-wire tendon is composed on a bundle of 7mm diameter wires with each wire fixed in to the anchorage with a multi-wire button head. Typical applications include Cable stay applications, re-stressable tendons, heavy lifting and lowering cables and coupled cables in incrementally launched bridges.

External Pre-stressing
External pre-stressing was first used in the 1920's. The SSL BBR Cona enables the pre-stressing cables to be placed externally of the structure or component so that no bond is present between the tendon and the structure except at the anchorage and deflector locations. The system lends itself to pre-stressing steel, timber, concrete and composite structures, as well as plastic materials. Typical applications include repair and strengthening of all types of structures and pre-cast segmental construction.