Post tensioning is actually a technique for reinforcing concrete. Post-tensioning tendons is stressing anchorage inside plastic ducts or sleeves, are situated in the forms prior to the concrete is put.” Post tension cables essentially allow us to safely build large concrete structures. They permit larger spans, thinner slabs and greater distances between support commons. Post tensioning is utilized in bridges and box girder structures worldwide including on our bridges, off and on ramps. These tendons make it possible to construct structures that may not otherwise be attainable. Because concrete is not bendable it may crack under loads. Although rebar can be 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 many benefits which can be gained simply by using a post-tensioned approach. It allows for flexibility of design, faster construction and reduce material costs. In the long run, it may reduce maintenance costs and allow 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 which can be difficult in case of regular bridges. This method reinforces or strengthens the concrete or some other material with high strength steel bar or strand which is called “tendons”. It significantly decreases the building weight and foundation load which is very useful in seismic areas.
Post tension tendons aid in construction of post tension anchorage that 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 reduces the effect on environment significantly.
Post tension tendons are made of prestressing strand, anchorage, ducts, and grout and corrosion protection materials. As 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 have become a significant problem.
Once you have details about tendon corrosion, department of transportation has inspected their post tension structure inventory to evaluate and quantify the pace of tendon corrosion and also to estimate the rest of the 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 may find corrosion and section loss inside a PT tendon.
What exactly it is? Since we have stated earlier that it is 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 includes a system to detect section loss in the tendon.
Why was it developed? During construction of complex bridges, tendons are completed grout to avoid corrosion. But during grouting process, the grout tends 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 vunerable to corrosion. Complex bridge inspection is incomplete without tendon testing therefore we have developed this TendonScan system to solve this challenge.
How it is used? This is a battery operated robotic system that utilizes the latest in non destructive testing and modern technology. This method couples itself with 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 along with the sensor. The sensor works through wireless connectivity to deliver the collected data. The details are transferred to control station for real time assessment from 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 could be identified and quantified easily.
What problem can it solve? This slab steel anchor works well for locating corrosion, voids, bleeding grout, section loss and other problems inside and outside the tendon. Moreover, it may also help in monitoring the discontinuities during a period of time which helps in deciding that if to fix or replace a post tension tendon.