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 actually a construction system called post tensioning and features allowed for many serious miracles in urban construction since its inception.
What exactly is Post Tensioning? Put simply, it is a way of Anchorage Barrel And Wedge, to make them stronger and much more resistant to cracking and breaking under environmental conditions. Concrete, when created and formed, can be very strong in their compressed form yet it is still relatively weak in other places. By bonding the concrete block during creation with stainless wires or rods, it improves its tensile strength, making the complete more durable to extreme changes.
The key advantage to creating concrete construction panels in this way is that it reduces the maintenance necessary to keep the structure as a whole fully operational. Whether the finished item is a slab foundation or even a nuclear containment wall, it is going to possess the flexibility it requires to resist temperature and environmental changes, less material will likely be needed to cover the identical area, a lighter structure weight overall along with a higher-level of structural integrity having a marked rise in deflection and vibration control. This technique is a boon to those areas which are 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. Since 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 installation of the finished panel.
The two main methods frequently used today in developing a post tensioned slab of concrete: wedge anchor. In the bonded method, a bonding grout is added to each channel through which the tensioning wires happen to be strung. This technique adds to the stability of the whole, further reducing maintenance costs in construction. Architecture designs that need greater flexibility, like those found in earthquake zones, will use the unbonded method, because they require greater flexibility, rather than additional reinforcement.
Typical steel strands found in post-tensioning use a tensile strength of 270,000 pounds/in². Compared, an average non-prestressed bit of reinforcing includes a tensile strength of 60,000 psi. Strands typically have a diameter of 1/2 in., and are stressed to your force of 33,000 pounds. The stresses brought in to the concrete counterbalance 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 after the concrete solidifies. The steel may then be stressed after the concrete sets. Normally, this is completed in two stages. The first prestress applied is up to 50% in the final force and this is done if the compressive strength reaches 12-15N/mm².
The next stage is when the pre-stressing anchor occurs and this is accomplished when the concrete meets its design strength. The strands and bars are tensioned by stretching these with a hydraulic jack. They are then fixed in position with an anchoring component, which supports the force in them for the life of your building. Post-tensioning allows the engineer to possess all of the benefits rwkhni using prestressed concrete whilst keeping the liberty of constructing at your location.
By far the most prominent markets for concrete that 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 durable slabs within their design. Within the private sector, constructions like hotels, universities, office buildings and condominiums have likewise taken advantage of this flexible alternative to traditional concrete installations. Need to know a little more about post tensioning processes and what kinds of forms can be produced for construction purposes?