Maybe 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 referred to as post tensioning and it has allowed for a few serious miracles in urban construction since its creation.
What exactly is Post Tensioning? Put simply, it really is a way of Post Tension Anchor, so they are stronger and a lot more immune to cracking and breaking under environmental conditions. Concrete, when created and formed, can be quite strong in the compressed form but 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 more durable to extreme changes.
The primary advantage to creating concrete construction panels in this fashion is that it cuts down on the maintenance needed to maintain the structure as a whole fully operational. If the finished product is a slab foundation or even a nuclear containment wall, it will possess the flexibility it needs to resist temperature and environmental changes, less material is going to be necessary to cover the identical area, a lighter structure weight overall and a more impressive range of structural integrity having a marked boost in deflection and vibration control. This process has become a boon to those areas that 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 size of a vacant concrete form 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 setting up the finished panel.
There are 2 methods widely used today in developing a post tensioned slab of concrete: anchorage grip. In the bonded method, a bonding grout is put into each channel whereby the tensioning wires have already been strung. This method increases the stability in the whole, further reducing maintenance costs in construction. Architecture designs that require greater flexibility, like those utilized in earthquake zones, uses the unbonded method, because they require greater flexibility, instead of additional reinforcement.
Typical steel strands utilized in post-tensioning possess a tensile strength of 270,000 pounds/in². In contrast, a typical non-prestressed part of reinforcing features a tensile strength of 60,000 psi. Strands typically have a diameter of 1/2 in., and therefore are stressed to some force of 33,000 pounds. The stresses brought to the concrete offset the expected external loads the concrete will be subjected to.
In post-tensioning the steel is held in a duct, which stops the steel and concrete from binding following the concrete solidifies. The steel are able to be stressed right after the concrete sets. Normally, this is done in two stages. The initial prestress applied is up to 50% in the final force and this is accomplished if the compressive strength reaches 12-15N/mm².
The 2nd stage occurs 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 them with a hydraulic jack. These are then fixed in place having an anchoring component, which holds the force within them for that life of your building. Post-tensioning allows the engineer to get all of the benefits rwkhni using prestressed concrete while keeping the freedom of constructing on location.
By far the most prominent markets for concrete that has been created through post tensioning represent the vast majority of installations that can 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 from this flexible alternative to traditional concrete installations. Want to find out a little more about post tensioning processes and what sorts of forms can be produced for construction purposes?