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 a construction system called post tensioning and it has allowed for some serious miracles in urban construction since its beginning.
What exactly is Post Tensioning? Put simply, it really is a method for Anchorhead, to make them stronger and more resistant to cracking and breaking under environmental conditions. Concrete, when created and formed, can be quite strong in their compressed form yet it is still relatively weak in other places. 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 key benefit to creating concrete construction panels in this fashion is that it cuts down on the maintenance needed to keep the structure as a whole fully operational. Whether or not the finished item is a slab foundation or a nuclear containment wall, it is going to hold the flexibility it must have to resist temperature and environmental changes, less material will be necessary to cover the same area, a lighter structure weight overall as well as a more impressive range of structural integrity having a marked increase in deflection and vibration control. This method is a boon to people areas which can be 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 duration of a vacant 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.
The two main methods widely used today in creating a post tensioned slab of concrete: wedge anchor. In the bonded method, a bonding grout is included in each channel by which the tensioning wires have been strung. This technique enhances the stability of 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, as opposed to additional reinforcement.
Typical steel strands utilized in post-tensioning possess a tensile strength of 270,000 pounds/in². Compared, an average non-prestressed piece of reinforcing has a tensile strength of 60,000 psi. Strands normally 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 will be exposed to.
In post-tensioning the steel is held in a duct, which stops the steel and concrete from binding right after the concrete solidifies. The steel are able to be stressed right after the concrete sets. Normally, this is completed in two stages. The initial prestress applied is up to 50% from the final force and this is achieved when the compressive strength reaches 12-15N/mm².
The second stage is when the slab steel anchor occurs and this is done if the concrete meets its design strength. The strands and bars are tensioned by stretching these with a hydraulic jack. They are then fixed set up having an anchoring component, which supports the force inside them for the lifetime of the property. Post-tensioning allows the engineer to get each of the benefits rwkhni using prestressed concrete and keep the liberty of constructing at your location.
Probably the most prominent markets for concrete which has been created through post tensioning represent nearly all 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 within their design. Within the private sector, constructions like hotels, universities, offices and condominiums have likewise taken benefit from this flexible option to traditional concrete installations. Want to find out more about post tensioning processes and what sorts of forms can be created for construction purposes?