Prestressed concrete is a concrete construction material which is placed under compression prior to it supporting any applied loads. This compression is produced by the tensioning of high-strength tendons located within or adjacent to the concrete volume, and is done to improve the performance of the concrete in service. Tendons may consist of single wires, multi-wire strands or threaded bars, and are most commonly made from high-tensile steels, carbon fibre or aramid fibre.
The essence of prestressed concrete is that once the initial compression has been applied, the resulting material has the characteristics of high-strength concrete when subject to any subsequent compression forces, and of ductile high-strength steel when subject to tension forces. This can result in improved structural capacity and serviceability compared to conventionally reinforced concrete in many situations.
Structural concrete is well known for its strength, durability and versatility. The use of pre-stressing enables concrete bridge beams to span long distances.Bridge beams can be used in beam-and-slab, solid slab and voided slab deck types and are suitable for simply supported, continuous and integral spans. Precast Concrete Beams are ideal for Road Bridges, Rail Bridges, Foot Bridges and any application incorporating long spans.
The video submitted by Steve Lowe, Chief Design Engineer associated with Shay Murtagh Precast shows the how the prestressing of the concrete precast beam is done. The importance of the prestressing and how it affects the compressibility, tensile strength and bending moment of the beam.