Post tensioning is a way of reinforcing 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 ultimately permit us to safely build large concrete constructions. They permit larger spans, thinner slabs and greater distances between support commons. Post tensioning is utilized in bridges and box girder structures globally including on our bridges, on / off ramps. These tendons have the ability to build structures that may not otherwise be feasible. Because concrete is not flexible it may crack under loads. Although rebar is used to strengthen the concrete to prevent cracks from growing the concrete can 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 numerous benefits which can be gained by using a post-tensioned approach. It allows for flexibility of design, faster construction and lower material costs. In the long run, it can reduce maintenance costs and allow for increased loads as time passes.
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 difficult in the event of regular bridges. This technique reinforces or strengthens the concrete or some other material rich in strength steel bar or strand which is known as “tendons”. It significantly cuts down on the building weight and foundation load which can be very helpful in seismic areas.
Post tension tendons assist in construction of post tension anchorage which includes specific geometry requirements such as complex curves and super elevation. Extremely long span bridges may be constructed with the aid of post tension tendons. Such architectures functions effectively without disrupting the traffic moving under it and also decreases the effect on environment significantly.
Post tension tendons are created from prestressing strand, anchorage, ducts, and grout and corrosion protection materials. As this technology is totally new therefore you can find no inspection systems for tendon components. Recent cases of corrosion of post tension tendons in complex bridges have become a substantial problem.
Once you have details about tendon corrosion, department of transportation has inspected their post tension structure inventory to gauge and quantify the pace of tendon corrosion and also to estimate the other lifespan from the affected member.
Infrastructure Preservation Corporation (IPC) has developed a comprehensive post tension tendon inspection service named “TendonScan®” which utilizes non destructive testing and evaluation methods that can find corrosion and section loss within a PT tendon.
What it is? As we have mentioned above 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 technique comes with a system to detect section loss inside the tendon.
Why was it developed? During construction of complex bridges, tendons are filled in grout to prevent corrosion. But during grouting process, the grout tends to separate according to 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 problem.
The actual way it is used? It really is a battery operated robotic system that utilizes the latest in non destructive testing and modern technology. This technique couples itself using the tendon and travel along it to carry out a MRI like inspection of smtzmh material inside it. The inspector stands on the mobile control unit which travels combined with the sensor. The sensor works through wireless connectivity to deliver the collected data. The information is moved to control station for real-time assessment in the tendon condition. The photo of internal portion of tendon will then be illustrated in 3D color graphics to ensure that any discontinuity like water intrusion, void or bleeding grout could be identified and quantified easily.
What problem does it solve? This pre-stressing anchor helps in locating corrosion, voids, bleeding grout, section loss along with other problems inside and outside the tendon. Moreover, it also helps in monitoring the discontinuities during a period of time that helps in deciding that whenever to correct or replace a post tension tendon.