Uses of Prestressed Concrete

There are a huge number of uses: • Railway Sleepers; • Communications poles; • Pre-tensioned precast “hollowcore” slabs; • Pre-tensioned Precast Double T units – for very long spans (e.g., 16 m span for car parks); • Pre-tensioned precast inverted T beam for short-span bridges; • Pre-tensioned precast PSC piles; • Pre-tensioned precast portal frame … Read more

Methods of Prestressing

There are two methods of prestressing: • Pre-tensioning: Apply prestress to steel strands before casting concrete; • Post-tensioning: Apply prestress to steel tendons after casting concrete. Pre-tensioning This is the most common form for precast sections. In Stage 1 the wires or strands are stressed; in Stage 2 the concrete is cast around the stressed … Read more

Basic Principle of Prestressing

The classic everyday example of prestressing is this:  A row of books can be lifted by squeezing the ends together: The structural explanation is that the row of books has zero tensile capacity. Therefore the ‘beam’ of books cannot even carry its self weight. To overcome this we provide an external initial stress (the prestress) which compresses the books together. Now they can only separate if the tensile stress induced by the self weight … Read more

Advantages of Prestressed Concrete

The main advantages of prestressed concrete (PSC) are: Smaller Section Sizes Since PSC uses the whole concrete section, the second moment of area is bigger and so the section is stiffer:     Smaller Deflections The larger second moment of area greatly reduces deflections for a given section size.   Increased Spans The smaller section size reduces self weight. Hence a given section can span  further with prestressed concrete than it can with ordinary reinforced concrete.   Durability Since the entire section remains in compression, no cracking of the concrete can occur and  hence there is little penetration of the cover. This greatly improves the long-term durability  of structures, especially bridges and also means that concrete tanks can be made as watertight  as steel tanks, with far greater durability.