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 pour concrete into a form to make the panels, so how do they do it? The key is a construction system called post tensioning and it has allowed for a few serious miracles in urban construction since its creation.
What is Post Tensioning? Put simply, it really is a way of Anchorhead, to ensure they are stronger and more resistant against 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 areas. By bonding the concrete block during creation with stainless-steel wires or rods, it improves its tensile strength, making the complete stronger to extreme changes.
The primary advantage to creating concrete construction panels in this fashion is it reduces the maintenance necessary to maintain the structure in general fully operational. Whether the finished item is a slab foundation or even a nuclear containment wall, it can have the flexibility it must have to resist temperature and environmental changes, less material will likely be required to cover exactly the same area, a lighter structure weight overall and a higher-level of structural integrity having a marked rise in deflection and vibration control. This process has been a boon to people areas which can be regularly plagued by earthquakes, and hurricanes.
How Will It Be Done? Tensioning strands of stainless wire, usually grouped into bundles, are stretched along the length of an empty concrete form before pouring. As the concrete hardens, the strands are tightened, “stressing” them through the hardening concrete. The strands are anchored by adjustable chucks, which is often loosened or tightened during setting up the finished panel.
There are 2 methods commonly used today in developing a post tensioned slab of concrete: anchorage grip. Within the bonded method, a bonding grout is put into each channel whereby the tensioning wires have been strung. This process enhances the stability of 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, since they require greater flexibility, rather than additional reinforcement.
Typical steel strands used in post-tensioning possess a tensile strength of 270,000 pounds/in². Compared, an average non-prestressed bit of reinforcing features a tensile strength of 60,000 psi. Strands normally have a diameter of 1/2 in., and are stressed to a force of 33,000 pounds. The stresses brought to the concrete counterbalance the expected external loads the concrete will likely be exposed 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 right after the concrete sets. Normally, this is carried out in two stages. The very first prestress applied is perfectly up to 50% from the final force and this is done once the compressive strength reaches 12-15N/mm².
The second 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 may be then fixed in position with an anchoring component, which supports the force within them for that lifetime of the building. Post-tensioning allows the engineer to have all of the benefits rwkhni using prestressed concrete and keep the freedom of constructing on site.
Probably the most prominent markets for concrete that has been created through post tensioning represent the majority of installations that are available 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 likewise taken advantage of this flexible substitute for traditional concrete installations. Want to know more about post tensioning processes and what types of forms can be created for construction purposes?