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 trick is actually a construction system known as post tensioning and features allowed for a few serious miracles in urban construction since its creation.
What is Post Tensioning? Put simply, it is a technique for Anchorage Barrel And Wedge, so they are stronger and a lot more resistant to cracking and breaking under environmental conditions. Concrete, when created and formed, can be quite 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 increases its tensile strength, making the whole more durable to extreme changes.
The main benefit to creating concrete construction panels in this fashion is it decreases the maintenance needed to maintain the structure as a whole fully operational. Whether or not the finished item 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 will be needed to cover the identical 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 those areas which can be 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 length of a vacant concrete form before pouring. As the concrete hardens, the strands are tightened, “stressing” them throughout the hardening concrete. The strands are anchored by adjustable chucks, which can be loosened or tightened during setting up the finished panel.
There are two methods widely used today in creating a post tensioned slab of concrete: anchorage grip. In the bonded method, a bonding grout is put into each channel whereby the tensioning wires happen to be strung. This process adds to the stability from the whole, further reducing maintenance costs in construction. Architecture designs that need greater flexibility, like those used in earthquake zones, will make use of the unbonded method, simply because they require greater flexibility, instead of additional reinforcement.
Typical steel strands found in post-tensioning use a tensile strength of 270,000 pounds/in². In contrast, a typical non-prestressed bit of reinforcing includes a tensile strength of 60,000 psi. Strands typically have a diameter of 1/2 in., and are stressed to your force of 33,000 pounds. The stresses brought into the concrete offset 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 following the concrete solidifies. The steel may then be stressed after the concrete sets. Normally, this is carried out in two stages. The first prestress applied is perfectly up to 50% from the final force and this is accomplished when the compressive strength reaches 12-15N/mm².
The 2nd stage happens when the slab steel anchor occurs and this is accomplished 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 holds the force within them for that life of the building. Post-tensioning allows the engineer to possess all the benefits rwkhni using prestressed concrete and keep the liberty of constructing on site.
By far 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 average city’s infrastructure. Airports, stadiums, parking garages, nuclear plants and roadways all incorporate these intricately created and sturdy slabs within their design. In the private sector, constructions like hotels, universities, offices and condominiums have also taken benefit of this flexible substitute for traditional concrete installations. Need to know more about post tensioning processes and what kinds of forms can be created for construction purposes?