Perhaps you have watched construction crews constructing 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 a construction system known as post tensioning and it has allowed for some serious miracles in urban construction since its creation.
Precisely what is Post Tensioning? Put simply, this is a method for Anchorhead, so they are stronger and much more resistant against cracking and breaking under environmental conditions. Concrete, when created and formed, can be quite strong in the compressed form but it is still relatively weak in other locations. By bonding the concrete block during creation with stainless wires or rods, it improves its tensile strength, making the entire more durable to extreme changes.
The key advantage to creating concrete construction panels in this way is it reduces the maintenance necessary to keep the structure overall fully operational. Whether the finished item is a slab foundation or even a nuclear containment wall, it will have the flexibility it must have to resist temperature and environmental changes, less material is going to be required to cover the identical area, a lighter structure weight overall along with a higher level of structural integrity using a marked increase in deflection and vibration control. This technique has become a boon to people areas that are regularly plagued by earthquakes, and hurricanes.
How Could It Be Done? Tensioning strands of stainless steel wire, usually grouped into bundles, are stretched along the length of an empty concrete form just before pouring. As the concrete hardens, the strands are tightened, “stressing” them through the entire hardening concrete. The strands are anchored by adjustable chucks, which can be loosened or tightened during setting up the finished panel.
There are two methods commonly used today in making a post tensioned slab of concrete: wedge anchor. In the bonded method, a bonding grout is included in each channel whereby the tensioning wires have been strung. This technique adds to the stability from the whole, further reducing maintenance costs in construction. Architecture designs which require greater flexibility, like those utilized in earthquake zones, uses the unbonded method, simply because they require greater flexibility, rather than additional reinforcement.
Typical steel strands used in post-tensioning possess a tensile strength of 270,000 pounds/in². In contrast, a normal non-prestressed piece of reinforcing includes a tensile strength of 60,000 psi. Strands routinely have a diameter of 1/2 in., and they are stressed to a force of 33,000 pounds. The stresses brought to the concrete offset the expected external loads the concrete will likely be subjected 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 can then be stressed right after the concrete sets. Normally, this is completed in two stages. The very first prestress applied is up to 50% from the final force and this is achieved when the compressive strength reaches 12-15N/mm².
The second stage occurs when the barrel and wedge anchor occurs and this is accomplished if the concrete meets its design strength. The strands and bars are tensioned by stretching them with a hydraulic jack. These are then fixed in position with an anchoring component, which supports the force in them for your lifetime of the property. Post-tensioning allows the engineer to get all of the benefits rwkhni using prestressed concrete while keeping the liberty of constructing on location.
By far the most prominent markets for concrete which has been created through post tensioning represent the vast majority of installations that can be found in the normal city’s infrastructure. Airports, stadiums, parking garages, nuclear plants and roadways all incorporate these intricately created and sturdy slabs to their design. In the private sector, constructions like hotels, universities, office buildings and condominiums have likewise taken benefit of this flexible substitute for traditional concrete installations. Want to know much more about post tensioning processes and what sorts of forms can be accomplished for construction purposes?