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 secret is actually a construction system called post tensioning and features allowed for many serious miracles in urban construction since its beginning.
What exactly is Post Tensioning? Put simply, it is a way of Anchorage Barrel And Wedge, so they are stronger and a lot more immune to cracking and breaking under environmental conditions. Concrete, when created and formed, can be very strong in the compressed form yet 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 stronger to extreme changes.
The main advantage to creating concrete construction panels in this fashion is it reduces the maintenance necessary to keep the structure in general fully operational. If the finished item is a slab foundation or a nuclear containment wall, it will possess the flexibility it must have to resist temperature and environmental changes, less material will likely be needed to cover the same area, a lighter structure weight overall and a higher-level of structural integrity with a marked increase in deflection and vibration control. This process 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 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 is often loosened or tightened during installation of the finished panel.
The two main methods commonly used today in developing a post tensioned slab of concrete: wedge anchor. In the bonded method, a bonding grout is put into each channel by which the tensioning wires happen to be strung. This technique enhances the stability from the whole, further reducing maintenance costs in construction. Architecture designs that need greater flexibility, like those used in earthquake zones, uses the unbonded method, since they require greater flexibility, instead of additional reinforcement.
Typical steel strands used in post-tensioning have a tensile strength of 270,000 pounds/in². In contrast, 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 your force of 33,000 pounds. The stresses brought to the concrete cancel out the expected external loads the concrete is going to be subjected 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 may then be stressed after the concrete sets. Normally, this is carried out in two stages. The first prestress applied depends on 50% of the final force and this is accomplished if the compressive strength reaches 12-15N/mm².
The 2nd stage is when the pre-stressing anchor occurs and this is done once the concrete meets its design strength. The strands and bars are tensioned by stretching all of them with a hydraulic jack. They are then fixed in position with an anchoring component, which holds the force inside them for your lifetime of the property. Post-tensioning allows the engineer to possess all of the benefits rwkhni using prestressed concrete while keeping the freedom of constructing on site.
Probably the most prominent markets for concrete that has been created through post tensioning represent the vast majority of installations that may be found in the typical 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 also have taken benefit of this flexible substitute for traditional concrete installations. Need to know more about post tensioning processes and what sorts of forms can be accomplished for construction purposes?