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 secret is actually a construction system known as post tensioning and features allowed for many serious miracles in urban construction since its creation.
What exactly is Post Tensioning? Put simply, it is a method for Post Tension Anchor, to ensure they are stronger and more immune to cracking and breaking under environmental conditions. Concrete, when created and formed, can be very strong in the compressed form but 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 advantage to creating concrete construction panels in this way is it decreases the maintenance required to keep the structure as a whole fully operational. Whether the finished item is a slab foundation or even a nuclear containment wall, it will hold the flexibility it needs to resist temperature and environmental changes, less material will likely be required to cover the identical area, a lighter structure weight overall and a higher-level of structural integrity with a marked boost in deflection and vibration control. This technique is a boon to those areas that are 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 duration of an empty concrete form just 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 frequently used today in creating a post tensioned slab of concrete: post tension anchorage. In the bonded method, a bonding grout is included in each channel through which 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, simply because they require greater flexibility, instead of additional reinforcement.
Typical steel strands used in post-tensioning possess a tensile strength of 270,000 pounds/in². In comparison, a normal non-prestressed piece of reinforcing features a tensile strength of 60,000 psi. Strands typically have a diameter of 1/2 in., and are stressed to some force of 33,000 pounds. The stresses brought in to the concrete counterbalance the expected external loads the concrete is going to be put through.
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 done in two stages. The very first prestress applied depends on 50% of the final force and this is achieved when the compressive strength reaches 12-15N/mm².
The next stage happens when the post stressed accessories occurs and this is done when the concrete meets its design strength. The strands and bars are tensioned by stretching them with a hydraulic jack. These are then fixed set up having an anchoring component, which holds the force in them for that life of the property. Post-tensioning allows the engineer to have all the benefits rwkhni using prestressed concrete whilst keeping the liberty of constructing on location.
The most prominent markets for concrete that has been created through post tensioning represent the majority of installations that may be found in the normal city’s infrastructure. Airports, stadiums, parking garages, nuclear plants and roadways all incorporate these intricately created and durable slabs within their design. Inside the private sector, constructions like hotels, universities, offices and condominiums also have taken advantage of this flexible alternative to traditional concrete installations. Want to find out much more about post tensioning processes and what types of forms can be created for construction purposes?