Have you ever 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 fill concrete into a form to make the panels, so how do they do it? The secret is a construction system known as post tensioning and it has allowed for many serious miracles in urban construction since its beginning.
What exactly is Post Tensioning? Put simply, it really is a method for Post Tension Anchor, to make them stronger and much more resistant to cracking and breaking under environmental conditions. Concrete, when created and formed, can be very strong in their compressed form but it is still relatively weak in other areas. By bonding the concrete block during creation with stainless steel wires or rods, it improves its tensile strength, making the entire stronger to extreme changes.
The primary benefit to creating concrete construction panels in this manner is that it reduces the maintenance necessary to keep your structure as a whole fully operational. If the finished product is a slab foundation or even a nuclear containment wall, it will hold the flexibility it must have to resist temperature and environmental changes, less material is going to be required to cover the same area, a lighter structure weight overall as well as a higher-level of structural integrity with a marked increase in deflection and vibration control. This technique has become a boon to the people areas which can be regularly plagued by earthquakes, and hurricanes.
How Could It Be Done? Tensioning strands of stainless wire, usually grouped into bundles, are stretched along the size of a vacant concrete form prior to pouring. As the concrete hardens, the strands are tightened, “stressing” them through the hardening concrete. The strands are anchored by adjustable chucks, which may be loosened or tightened during installing of the finished panel.
There are 2 methods frequently used today in creating a post tensioned slab of concrete: dead-end anchorage. In the bonded method, a bonding grout is included in each channel through which the tensioning wires have already been strung. This technique adds to the stability of the whole, further reducing maintenance costs in construction. Architecture designs that need greater flexibility, like those found in earthquake zones, uses the unbonded method, since they require greater flexibility, as opposed to additional reinforcement.
Typical steel strands used in post-tensioning use a tensile strength of 270,000 pounds/in². Compared, a typical non-prestressed bit of reinforcing features 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 counterbalance the expected external loads the concrete is going to 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 following the concrete sets. Normally, this is carried out in two stages. The initial prestress applied depends on 50% in the final force and this is accomplished once the compressive strength reaches 12-15N/mm².
The next stage is when the pre-stressing anchor occurs and this is accomplished when the concrete meets its design strength. The strands and bars are tensioned by stretching these with a hydraulic jack. They may be then fixed set up having an anchoring component, which supports the force within them for your life of the building. Post-tensioning allows the engineer to have all the benefits rwkhni using prestressed concrete while keeping the freedom of constructing at your location.
Probably the most prominent markets for concrete which has been created through post tensioning represent nearly all 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 alternative to traditional concrete installations. Need to know much more about post tensioning processes and what types of forms can be created for construction purposes?