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 fill 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 a few serious miracles in urban construction since its creation.
What exactly is Post Tensioning? Put simply, it is a technique for Anchorhead, so they are stronger and much more immune to cracking and breaking under environmental conditions. Concrete, when created and formed, can be very strong in its compressed form however 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 whole stronger to extreme changes.
The key advantage to creating concrete construction panels in this way is it reduces the maintenance necessary to keep the structure as a whole fully operational. Whether or not the finished item is a slab foundation or even a nuclear containment wall, it is going to hold the flexibility it needs to resist temperature and environmental changes, less material will be needed to cover the same 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 method has become a boon to those 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 duration of an empty 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 can be loosened or tightened during installing of the finished panel.
There are 2 methods widely used today in making a post tensioned slab of concrete: wedge anchor. Inside the bonded method, a bonding grout is put into each channel whereby the tensioning wires happen to be strung. This method increases the stability from the whole, further reducing maintenance costs in construction. Architecture designs that need greater flexibility, like those found in earthquake zones, uses the unbonded method, simply because they require greater flexibility, as opposed to additional reinforcement.
Typical steel strands utilized in post-tensioning have a tensile strength of 270,000 pounds/in². In contrast, an average non-prestressed bit of reinforcing features a tensile strength of 60,000 psi. Strands routinely have a diameter of 1/2 in., and therefore are stressed to your force of 33,000 pounds. The stresses brought into the concrete counterbalance the expected external loads the concrete will likely 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 right after the concrete sets. This is usually completed in two stages. The first prestress applied depends on 50% of the final force and this is done if the compressive strength reaches 12-15N/mm².
The second stage happens when the barrel and wedge anchor occurs and this is done once the concrete meets its design strength. The strands and bars are tensioned by stretching these with a hydraulic jack. They are then fixed in place having an anchoring component, which supports the force in them for that life of the property. Post-tensioning allows the engineer to get each of the benefits rwkhni using prestressed concrete while keeping the freedom of constructing on site.
Probably the most prominent markets for concrete that has been created through post tensioning represent the vast majority of installations that are available in the typical city’s infrastructure. Airports, stadiums, parking garages, nuclear plants and roadways all incorporate these intricately created and durable slabs within their design. In the private sector, constructions like hotels, universities, office buildings and condominiums also have taken advantage of this flexible substitute for traditional concrete installations. Want to know much more about post tensioning processes and what types of forms can be produced for construction purposes?