Maybe you have watched construction crews building a parking garage or skyscraper and wondered how they were able to raise and attach huge concrete panels like they were building blocks? You never see them actually pour concrete into a form to make the panels, so how do they do it? The trick is actually a construction system called post tensioning and it has allowed for a few serious miracles in urban construction since its beginning.
Precisely what is Post Tensioning? Put simply, this is a technique for Anchorage Barrel And Wedge, so they are stronger and a lot more resistant against cracking and breaking under environmental conditions. Concrete, when created and formed, can be quite strong in the compressed form however it is still relatively weak in other areas. By bonding the concrete block during creation with stainless wires or rods, it increases its tensile strength, making the whole stronger to extreme changes.
The key benefit to creating concrete construction panels in this manner is it decreases the maintenance needed to keep your structure as a whole fully operational. Whether the finished item is a slab foundation or perhaps a nuclear containment wall, it is going to hold the flexibility it requires to resist temperature and environmental changes, less material will be needed to cover the identical area, a lighter structure weight overall and a more impressive range of structural integrity having a marked increase in deflection and vibration control. This process is a boon to those areas that are regularly plagued by earthquakes, and hurricanes.
How Is It Done? Tensioning strands of stainless-steel wire, usually grouped into bundles, are stretched along the size of a vacant concrete form before pouring. Because the concrete hardens, the strands are tightened, “stressing” them through the entire hardening concrete. The strands are anchored by adjustable chucks, which may be loosened or tightened during setting up the finished panel.
There are 2 methods commonly used today in developing a post tensioned slab of concrete: anchorage grip. In the bonded method, a bonding grout is added to each channel through which the tensioning wires happen to be strung. This technique increases the stability in the whole, further reducing maintenance costs in construction. Architecture designs that require greater flexibility, like those used in earthquake zones, uses the unbonded method, since they require greater flexibility, instead of additional reinforcement.
Typical steel strands found in post-tensioning have a tensile strength of 270,000 pounds/in². In contrast, an average non-prestressed piece of reinforcing includes a tensile strength of 60,000 psi. Strands normally have a diameter of 1/2 in., and therefore are stressed to a force of 33,000 pounds. The stresses brought in to the concrete offset the expected external loads the concrete will likely be exposed to.
In post-tensioning the steel is held in a duct, which stops the steel and concrete from binding following the concrete solidifies. The steel may then be stressed right after the concrete sets. This is usually completed in two stages. The initial prestress applied is up to 50% in the final force and this is accomplished when the compressive strength reaches 12-15N/mm².
The next stage happens when the barrel and wedge anchor occurs and this is accomplished once the concrete meets its design strength. The strands and bars are tensioned by stretching these with a hydraulic jack. They may be then fixed in position having an anchoring component, which holds the force within them for that lifetime of your building. Post-tensioning allows the engineer to possess all the benefits rwkhni using prestressed concrete while keeping the liberty of constructing at your location.
The most prominent markets for concrete which has been created through post tensioning represent nearly all installations that may be found in the average city’s infrastructure. Airports, stadiums, parking garages, nuclear plants and roadways all incorporate these intricately created and durable slabs to their design. Inside the private sector, constructions like hotels, universities, office buildings and condominiums have also taken benefit of this flexible option to traditional concrete installations. Want to know more about post tensioning processes and what kinds of forms can be accomplished for construction purposes?