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 fill 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 features allowed for a few serious miracles in urban construction since its inception.
What exactly is Post Tensioning? Put simply, it is a technique for Post Tension Anchor, to make them stronger and a lot 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 locations. By bonding the concrete block during creation with stainless steel wires or rods, it increases its tensile strength, making the entire more durable to extreme changes.
The main advantage to creating concrete construction panels in this manner is it cuts down on the maintenance necessary to keep your structure in general fully operational. Whether the finished item is a slab foundation or even a nuclear containment wall, it is going to possess the flexibility it must have to resist temperature and environmental changes, less material is going to be necessary to cover the identical area, a lighter structure weight overall as well as a higher level of structural integrity having a marked boost in deflection and vibration control. This technique has become a boon to those areas which are regularly plagued by earthquakes, and hurricanes.
How Will It Be Done? Tensioning strands of stainless-steel wire, usually grouped into bundles, are stretched along the duration of an empty concrete form prior to pouring. As 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 two methods widely used today in creating a post tensioned slab of concrete: dead-end anchorage. Within the bonded method, a bonding grout is included in each channel by which the tensioning wires have been strung. This process adds to the stability in the whole, further reducing maintenance costs in construction. Architecture designs that need greater flexibility, like those utilized in earthquake zones, will make use of the unbonded method, because they require greater flexibility, rather than additional reinforcement.
Typical steel strands found in post-tensioning use a tensile strength of 270,000 pounds/in². In comparison, an average non-prestressed piece of reinforcing has a tensile strength of 60,000 psi. Strands routinely 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 will likely 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 may then be stressed right after the concrete sets. Normally, this is carried out in two stages. The first prestress applied is up to 50% from the final force and this is achieved once the compressive strength reaches 12-15N/mm².
The second stage occurs when the post stressed accessories occurs and this is done if the concrete meets its design strength. The strands and bars are tensioned by stretching them with a hydraulic jack. These are then fixed set up having an anchoring component, which supports the force within them for that life of your building. Post-tensioning allows the engineer to have all the benefits rwkhni using prestressed concrete while keeping the liberty of constructing on location.
Probably the most prominent markets for concrete which has been created through post tensioning represent the majority of installations that can be found in the average 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, offices and condominiums have also taken benefit from this flexible substitute for traditional concrete installations. Want to find out more about post tensioning processes and what sorts of forms can be created for construction purposes?