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 key is actually a construction system referred to as post tensioning and it has allowed for some serious miracles in urban construction since its creation.
Precisely what is Post Tensioning? Put simply, it is a way of Post Tension Anchor, to make them stronger and much more resistant to 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 wires or rods, it improves its tensile strength, making the entire stronger to extreme changes.
The main benefit to creating concrete construction panels in this fashion is it reduces the maintenance required to keep your structure as a whole fully operational. If the finished item is a slab foundation or a nuclear containment wall, it will have the flexibility it requires to resist temperature and environmental changes, less material will likely be required to cover exactly the same area, a lighter structure weight overall along with a higher-level of structural integrity with a marked boost in deflection and vibration control. This method has become a boon to the people areas which 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 is often loosened or tightened during setting up the finished panel.
There are two methods frequently used today in creating a post tensioned slab of concrete: wedge anchor. Within the bonded method, a bonding grout is added to each channel whereby the tensioning wires have been strung. This method adds to the stability from the whole, further reducing maintenance costs in construction. Architecture designs which require greater flexibility, like those found in earthquake zones, uses the unbonded method, because they require greater flexibility, instead of additional reinforcement.
Typical steel strands utilized in post-tensioning possess a tensile strength of 270,000 pounds/in². In comparison, an average non-prestressed piece of reinforcing includes a tensile strength of 60,000 psi. Strands routinely have a diameter of 1/2 in., and therefore are stressed to some force of 33,000 pounds. The stresses brought into the concrete cancel out the expected external loads the concrete will be subjected to.
In post-tensioning the steel is held in a duct, which stops the steel and concrete from binding after the concrete solidifies. The steel are able to be stressed right after the concrete sets. This is usually carried out in two stages. The first prestress applied depends on 50% in the final force and this is done when the compressive strength reaches 12-15N/mm².
The 2nd stage is when the slab steel anchor occurs and this is achieved once the concrete meets its design strength. The strands and bars are tensioned by stretching them with a hydraulic jack. They may be then fixed set up having an anchoring component, which supports the force inside them for that life of the property. Post-tensioning allows the engineer to possess all the benefits rwkhni using prestressed concrete while keeping the freedom of constructing on location.
The most prominent markets for concrete that 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 within their design. Inside the private sector, constructions like hotels, universities, offices and condominiums also have taken benefit of this flexible option to traditional concrete installations. Need to know much more about post tensioning processes and what sorts of forms can be created for construction purposes?