Post tensioning is a way of reinforcing concrete. Post-tensioning tendons is Barrel And Wedges inside plastic ducts or sleeves, are situated in the forms before the concrete is placed.” Post tension cables in effect permit us to safely build large concrete structures. They enable larger spans, thinner slabs and greater distances between support commons. Post tensioning is used in bridges and box girder structures globally such as on our bridges, off and on ramps. These tendons make it possible to build structures which may not be feasible. Because concrete is not flexible it can crack under loads. Although rebar is utilized to strengthen the concrete to prevent cracks from growing the concrete can certainly still sag under increased loads. PT or post tension tendons are load bearing and may stand large increases in loads bearing up the concrete.
There are many benefits which are gained simply by using a post-tensioned approach. It allows for flexibility of design, faster construction and lower material costs. Over time, it could reduce maintenance costs and enable for increased loads over time.
Bridges that utilize post tension tendons are able to contain long and clear spans, have few beams and slender members and thinner slabs can be utilized that is unachievable in the case of regular bridges. This process reinforces or strengthens the concrete or some other material with higher strength steel bar or strand which is known as “tendons”. It significantly reduces the building weight and foundation load which can be very useful in seismic areas.
Post tension tendons help in construction of anchorage grip that has specific geometry requirements including complex curves and super elevation. Extremely long span bridges may be constructed through the help of post tension tendons. Such architectures functions effectively without disrupting the traffic moving under it and also decreases the influence on environment significantly.
Post tension tendons are made of prestressing strand, anchorage, ducts, and grout and corrosion protection materials. As this technology is new therefore you will find no inspection systems for tendon components. Recent cases of corrosion of post tension tendons in complex bridges have grown to be a significant problem.
Once you have information about tendon corrosion, department of transportation has inspected their post tension structure inventory to assess and quantify the rate of tendon corrosion and also to estimate the remaining lifespan in the affected member.
Infrastructure Preservation Corporation (IPC) has created a thorough post tension tendon inspection service named “TendonScan®” which utilizes non destructive testing and evaluation methods that may find corrosion and section loss inside a PT tendon.
What exactly it is? As we have mentioned previously that it is a thorough tendon scanning system which works on non destructive testing principals to learn voids, water intrusion and bleeding grout in external tendons. This system includes a system to detect section loss in the tendon.
Why was it developed? During construction of complex bridges, tendons are filled in grout to stop corrosion. But during grouting process, the grout has a tendency to separate depending on grout’s quality, admixtures, pumping equipment and operations. This separation result into low pH grout at tendon points and anchorage which made these locations susceptible to corrosion. Complex bridge inspection is incomplete without tendon testing therefore we have developed this TendonScan system to solve this challenge.
The way it is used? It really is a battery operated robotic system that utilizes the latest in non destructive testing and modern technology. This system couples itself with all the tendon and travel along it to perform a MRI like inspection of smtzmh material inside it. The inspector stands on the mobile control unit which travels together with the sensor. The sensor works through wireless connectivity to send out the collected data. The details are transferred to control station for live assessment of the tendon condition. The picture of internal part of tendon is then illustrated in 3D color graphics in order that any discontinuity like water intrusion, void or bleeding grout could be identified and quantified easily.
What problem can it solve? This pre-stressing anchor works well for locating corrosion, voids, bleeding grout, section loss along with other problems outside and inside the tendon. Moreover, it also helps in monitoring the discontinuities over a duration of time which will help in deciding that whenever to repair or replace a post tension tendon.