Post tensioning is a way of strengthening concrete. Post-tensioning tendons is Barrel And Wedges inside plastic ducts or sleeves, are positioned in the forms ahead of the concrete is put.” Post tension cables essentially let us safely build large concrete constructions. They enable larger spans, thinner slabs and greater distances between support commons. Post tensioning can be used in bridges and box girder structures worldwide such as on our bridges, off and on ramps. These tendons make it possible to develop structures which may not be feasible. Because concrete is not flexible it may crack under loads. Although rebar is utilized to reinforce 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 will stand large increases in loads bearing up the concrete.
There are many benefits which can be gained by using a post-tensioned approach. It provides for flexibility of design, faster construction and minimize material costs. Over the long term, it could reduce maintenance costs and allow for increased loads with time.
Bridges that utilize post tension tendons have the ability to contain long and clear spans, have few beams and slender members and thinner slabs can be used which can be not possible in the case of regular bridges. This technique reinforces or strengthens the concrete or other material with high strength steel bar or strand which is called “tendons”. It significantly cuts down on the building weight and foundation load that is very helpful in seismic areas.
Post tension tendons assist in construction of dead-end anchorage which has specific geometry requirements including complex curves and super elevation. Extremely long span bridges may be constructed with the help of post tension tendons. Such architectures functions effectively without disrupting the traffic moving under it as well as decreases the impact on environment significantly.
Post tension tendons are made from prestressing strand, anchorage, ducts, and grout and corrosion protection materials. Because this technology is totally 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 substantial problem.
After getting details about tendon corrosion, department of transportation has inspected their post tension structure inventory to assess and quantify the rate of tendon corrosion as well as estimate the rest of the lifespan of 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 can find corrosion and section loss in a PT tendon.
What exactly it is? As we have mentioned previously that it must be a thorough tendon scanning system which works on non destructive testing principals to find out voids, water intrusion and bleeding grout in external tendons. This system also includes a device to detect section loss within 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 based on grout’s quality, admixtures, pumping equipment and procedures. This separation result into low pH grout at tendon points and anchorage which made these locations vunerable to corrosion. Complex bridge inspection is incomplete without tendon testing therefore we have now developed this TendonScan system to settle this issue.
The way it can be used? It really is a battery operated robotic system that utilizes the newest in non destructive testing and modern technology. This method couples itself with the tendon and travel along it to perform a MRI like inspection of smtzmh material within it. The inspector stands on the mobile control unit which travels combined with the sensor. The sensor works through wireless connectivity to transmit the collected data. The information is moved to control station for real-time assessment in the tendon condition. The picture of internal section of tendon will be illustrated in 3D color graphics in order that any discontinuity like water intrusion, void or bleeding grout can be identified and quantified easily.
What problem can it solve? This post stressed anchor works well for locating corrosion, voids, bleeding grout, section loss as well as other problems outside and inside the tendon. Moreover, it can also help in monitoring the discontinuities over a duration of time that helps in deciding that whenever to correct or replace a post tension tendon.