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 secret is a construction system referred to as post tensioning and it has allowed for some serious miracles in urban construction since its beginning.
What is Post Tensioning? Put simply, it is a way of Anchorage Barrel And Wedge, to ensure they are stronger and much more resistant to 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 entire more durable to extreme changes.
The key advantage to creating concrete construction panels in this fashion is that it cuts down on the maintenance required to keep your structure in general fully operational. If the finished product is a slab foundation or even a nuclear containment wall, it will possess the flexibility it needs to resist temperature and environmental changes, less material is going to be required to cover exactly the same area, a lighter structure weight overall along with a higher-level of structural integrity having a marked increase in deflection and vibration control. This method has become a boon to people areas which are regularly plagued by earthquakes, and hurricanes.
How Is It Done? Tensioning strands of stainless wire, usually grouped into bundles, are stretched along the length of a vacant concrete form prior to pouring. Because the concrete hardens, the strands are tightened, “stressing” them throughout the hardening concrete. The strands are anchored by adjustable chucks, which may be loosened or tightened during installation of the finished panel.
There are 2 methods commonly used today in developing a post tensioned slab of concrete: dead-end anchorage. In the bonded method, a bonding grout is included in each channel by which the tensioning wires have been strung. This process increases 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 utilized in post-tensioning use a tensile strength of 270,000 pounds/in². In comparison, an average non-prestressed bit of reinforcing includes a tensile strength of 60,000 psi. Strands typically have a diameter of 1/2 in., and therefore are stressed to some force of 33,000 pounds. The stresses brought into the concrete offset the expected external loads the concrete is going to 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 are able to be stressed right after the concrete sets. This is usually done in two stages. The very first prestress applied is up to 50% in the final force and this is done when the compressive strength reaches 12-15N/mm².
The next stage is when the post stressed accessories occurs and this is accomplished once the concrete meets its design strength. The strands and bars are tensioned by stretching all of them with a hydraulic jack. They may be then fixed set up with the anchoring component, which holds the force inside them for the lifetime of your building. Post-tensioning allows the engineer to possess each of the benefits rwkhni using prestressed concrete and keep the freedom of constructing at your location.
Probably 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 into their design. Inside the private sector, constructions like hotels, universities, office buildings and condominiums have also taken benefit from this flexible substitute for traditional concrete installations. Need to know much more about post tensioning processes and what sorts of forms can be created for construction purposes?