Post-tensioning
More durable concrete constructions with post-tensioning
Prestressed reinforcement is a method of reinforcing concrete and is used to create stronger and more durable concrete structures. Strands of high-strength steel are placed in ducts either before or after the concrete is placed. When the concrete has gained strength, the strand cables are tensioned and anchored to the outer edges of the concrete. This creates a compression of the concrete and lift in the structure that counteracts tensile stress.
Advantages of post-tensioning:
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Higher strength: Post-tensioned concrete is up to 50% stronger than traditional reinforced concrete. This makes it an ideal choice for structures subject to high loads, such as bridges and tall buildings.
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Less cracking: Post-tensioned concrete is less prone to cracking than traditional reinforced concrete. Smaller cracks mean the construction is more resistant to corrosion and moisture ingress, improving its durability.
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Lower costs: Post-tensioned concrete can be used to create thinner concrete structures. This leads to lower construction costs and less environmental impact.
Post-tensioned bridges and other structures
Although post-tensioning is a well-established technique, it is still a great tool for the designer as it enables the active definition of the internal load path in concrete structures by bridging a favorable condition of the internal stresses. This makes it possible to minimize deformations, helps to reduce the thickness of the beams, reduces congestion in the reinforcement, facilitates segmental construction without the need for wet joints and allows the use of high strength steel.
Post-tensioning is an important structural reinforcement of a concrete structure and can be used in bridges, buildings, tank facilities, dams and other types of structures subjected to pure tensile or bending stress or a combination of these types of loading.
It consists in introducing an internal state of tension in a concrete element, with the installation and tensioning of steel cables laid in ducts in the concrete structure. This will counteract stresses due to external loading and reduce deformation and cracking of concrete. The VSL System has a European technical approval number ETA-06/0006
Ground Anchors
VSL's Ground-anchors secures loads deep into the ground and is used in a variety of ways, including stabilizing huge excavations, steep slopes and gigantic structures. VSL's ground-anchors is used all over the world – and secures many famous structures, monumental dams and retaining walls. They are also used to hold down pedestrian tunnels and underground structures, stabilize wind towers and prevent landslides. The ground-anchors provide a competitive alternative to heavy-duty stabilization of structures, as they drive forces into the ground through their tension elements. The choice of ground-anchors depends on factors such as whether they will be under tension or not, used in rock or soil, or whether they are used for temporary or permanent use.
VSL's ground anchors have a Swiss technical approval number STA - 02/002.
Stress bars
Stress bars provide impressive versatility in geotechnical and structural applications to control loads and forces in the structure. Stress bars have a wide range of applications in the construction and mining industries.
The function of stress bars depends on how they are used, implemented and ultimately on their ultimate purpose:
• geotechnical systems such as soil spikes, micropiles and rock bolts
• concrete reinforcement system
• post-tensioning system
• marine tie rod systems
• anchor and form tie system
Post-tensioning for nuclear power:
Post-tensioning occurs in all Swedish nuclear power plants, where primarily the reactor containments and some reactor/fuel pools are heavily reinforced with post-tensioning. The primary task of post-tensioning is to limit cracking and deformation in the concrete structure. For reactor containments, where high demands are placed on the tightness of the constructions, a satisfactory function of the post-tension cable system is of great importance.
VSL post-tensioning systems have been used in many nuclear power plants worldwide, including in Sweden in the power plants Barsebäck 1 and 2, Oskarshamn 3, Forsmark 1 and Forsmark 2.
Modern nuclear power plants where VSL's post-tensioning system is represented are, for example, Hinkley Point C in the UK, the Olkiluoto nuclear power plant in Finland and the Flamanville nuclear power plant in France.
Post-tensioned slab on ground
Slab on ground is today the most common form of foundation and means that a reinforced and insulated concrete slab forms the bottom joist of the construction.
Post-tensioned slab on ground is more durable and economical than conventionally reinforced slabs on ground. The benefits of faster construction times while reducing the amount of concrete and rebar, save money.
The post-tensioning provides an internal compressive force in the concrete. This increases resistance to deflections and cracking caused by expansive soil problems such as heaving, shrinkage or swelling due to temperature or moisture changes. This ensures superior durable high-quality surfaces in a variety of applications as well as reducing and in some cases completely eliminating the number of casting joints.
Post-tensioned slab on ground significantly improves performance and durability especially for Industrial and commercial floors.
