Post tensioning is actually a way of reinforcing concrete. Post-tensioning tendons is Post Tension Anchor inside plastic ducts or sleeves, are positioned in the forms before the concrete is put.” Post tension cables ultimately let us safely build large concrete structures. They permit larger spans, thinner slabs and greater distances between support commons. Post tensioning can be used in bridges and box girder structures worldwide including on our bridges, off and on ramps. These tendons have the ability to build structures that may not otherwise be feasible. Because concrete is not bendable it can crack under loads. Although rebar is utilized to strengthen the concrete to stop cracks from growing the concrete can certainly still sag under increased loads. PT or post tension tendons are load bearing and can stand large increases in loads bearing up the concrete.
There are many benefits which are gained using a post-tensioned approach. It provides for flexibility of design, faster construction and reduce material costs. In the long run, it may reduce maintenance costs and allow for increased loads with time.
Bridges that utilize post tension tendons can contain long and clear spans, have few beams and slender members and thinner slabs can be used that is unachievable in the case of regular bridges. This method reinforces or strengthens the concrete or any other material with high 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 dead-end anchorage which includes specific geometry requirements such as complex curves and super elevation. Extremely long span bridges can be constructed through the help of post tension tendons. Such architectures functions effectively without disrupting the traffic moving under it as well as cuts down on the influence on environment significantly.
Post tension tendons are made of prestressing strand, anchorage, ducts, and grout and corrosion protection materials. Since this technology is completely new therefore you can find no inspection systems for tendon components. Recent cases of corrosion of post tension tendons in complex bridges are becoming an important problem.
Once you have details about tendon corrosion, department of transportation has inspected their post tension structure inventory to evaluate and quantify the rate of tendon corrosion and to estimate the remaining lifespan from the affected member.
Infrastructure Preservation Corporation (IPC) has evolved a comprehensive post tension tendon inspection service named “TendonScan®” which utilizes non destructive testing and evaluation methods that can find corrosion and section loss inside a PT tendon.
What exactly it is? As we have stated earlier that it must be a thorough tendon scanning system which works on non destructive testing principals to discover voids, water intrusion and bleeding grout in external tendons. This method comes with a product to detect section loss within the tendon.
Why was it developed? During construction of complex bridges, tendons are completed grout to prevent corrosion. But during grouting process, the grout tends 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 susceptible to corrosion. Complex bridge inspection is incomplete without tendon testing therefore we have developed this TendonScan system to resolve this problem.
How it can be used? This is a battery operated robotic system that utilizes the latest in non destructive testing and modern technology. This technique couples itself with all 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 details are moved to control station for real-time assessment from the tendon condition. The image of internal portion of tendon will be illustrated in 3D color graphics so that any discontinuity like water intrusion, void or bleeding grout can be identified and quantified easily.
What problem will it solve? This post stressed anchor helps in 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 period of time that helps in deciding that when to fix or replace a post tension tendon.