Have you ever 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 secret is actually a construction system referred to as post tensioning and it has allowed for a few serious miracles in urban construction since its beginning.
What is Post Tensioning? Put simply, it is a technique for Anchorhead, to ensure they are stronger and more resistant against cracking and breaking under environmental conditions. Concrete, when created and formed, could be very strong in its compressed form yet it is still relatively weak in other places. By bonding the concrete block during creation with stainless steel 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 that it decreases the maintenance required to keep your structure overall fully operational. Whether or not the finished item is a slab foundation or perhaps a nuclear containment wall, it can hold the flexibility it must have to resist temperature and environmental changes, less material will likely be needed to cover exactly the same area, a lighter structure weight overall and a higher-level of structural integrity using a marked boost in deflection and vibration control. This technique has been a boon to people 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 length of an empty concrete form just before pouring. Since the concrete hardens, the strands are tightened, “stressing” them throughout the hardening concrete. The strands are anchored by adjustable chucks, which can be loosened or tightened during installation of the finished panel.
There are two methods frequently used today in making a post tensioned slab of concrete: dead-end anchorage. Inside the bonded method, a bonding grout is put into each channel whereby the tensioning wires happen to be strung. This technique enhances 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, because they require greater flexibility, as opposed to additional reinforcement.
Typical steel strands utilized in post-tensioning use a tensile strength of 270,000 pounds/in². Compared, a typical non-prestressed piece of reinforcing features a tensile strength of 60,000 psi. Strands typically have a diameter of 1/2 in., and are stressed to your force of 33,000 pounds. The stresses brought in to the concrete counterbalance the expected external loads the concrete is going to be put through.
In post-tensioning the steel is held in a duct, which stops the steel and concrete from binding following the concrete solidifies. The steel are able to be stressed following the concrete sets. Normally, this is completed in two stages. The initial prestress applied is up to 50% of the final force and this is accomplished if the compressive strength reaches 12-15N/mm².
The second stage occurs when the pre-stressing anchor occurs and this is achieved if the concrete meets its design strength. The strands and bars are tensioned by stretching them with a hydraulic jack. They are then fixed set up with an anchoring component, which supports the force inside them for that lifetime of the property. Post-tensioning allows the engineer to have all the benefits rwkhni using prestressed concrete whilst keeping the liberty of constructing on location.
The most prominent markets for concrete that has been created through post tensioning represent nearly all installations that are available 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 from this flexible alternative to traditional concrete installations. Want to know a little more about post tensioning processes and what kinds of forms can be produced for construction purposes?