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 secret is actually a construction system referred to as post tensioning and features allowed for a few serious miracles in urban construction since its inception.
What exactly is Post Tensioning? Put simply, it really is a method for Anchorage Barrel And Wedge, to make them stronger and much more resistant to cracking and breaking under environmental conditions. Concrete, when created and formed, could be very strong in their compressed form yet it is still relatively weak in other locations. By bonding the concrete block during creation with stainless steel wires or rods, it improves its tensile strength, making the whole more durable to extreme changes.
The main benefit to creating concrete construction panels in this fashion is that it decreases the maintenance needed to maintain the structure overall fully operational. Whether or not the finished item is a slab foundation or a nuclear containment wall, it can possess the flexibility it must have to resist temperature and environmental changes, less material is going to be necessary to cover the identical area, a lighter structure weight overall as well as a higher-level of structural integrity with a marked increase in deflection and vibration control. This method has been a boon to the people 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 an empty concrete form before pouring. Because 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 installation of the finished panel.
The two main methods frequently used today in making a post tensioned slab of concrete: anchorage grip. Within the bonded method, a bonding grout is included in each channel whereby the tensioning wires have been strung. This technique adds to the stability from the whole, further reducing maintenance costs in construction. Architecture designs which require greater flexibility, like those utilized in earthquake zones, will use the unbonded method, since they require greater flexibility, rather than additional reinforcement.
Typical steel strands found in post-tensioning use a tensile strength of 270,000 pounds/in². In comparison, a normal non-prestressed piece of reinforcing has a tensile strength of 60,000 psi. Strands routinely 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 likely be subjected to.
In post-tensioning the steel is held in a duct, which stops the steel and concrete from binding after the concrete solidifies. The steel are able to be stressed following the concrete sets. Normally, this is completed in two stages. The initial prestress applied is perfectly up to 50% of the final force and this is achieved once the compressive strength reaches 12-15N/mm².
The second stage happens when the barrel and wedge anchor occurs and this is done if the concrete meets its design strength. The strands and bars are tensioned by stretching them with a hydraulic jack. They may be then fixed in position having an anchoring component, which holds the force inside them for that life of the property. Post-tensioning allows the engineer to have each of the benefits rwkhni using prestressed concrete and keep the freedom of constructing at your location.
Probably 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 sturdy slabs to their design. In the private sector, constructions like hotels, universities, offices and condominiums have also taken benefit 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 accomplished for construction purposes?