Post tensioning is actually a way of reinforcing concrete. Post-tensioning tendons is Post Tension Anchor inside plastic ducts or sleeves, are situated in the forms prior to the concrete is placed.” Post tension cables in effect let us safely build large concrete structures. They allow larger spans, thinner slabs and greater distances between support commons. Post tensioning can be used in bridges and box girder structures globally including on our bridges, on and off ramps. These tendons make it possible to construct structures that may not otherwise be possible. Because concrete is not bendable it can crack under loads. Although rebar is used to strengthen the concrete to stop cracks from growing the concrete can 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 numerous benefits which can be gained 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 may be used which is unachievable in the 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 cuts down on the building weight and foundation load which is very useful in seismic areas.
Post tension tendons help in construction of anchorage grip that has specific geometry requirements like 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 created from 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 are becoming an important problem.
Once you have information about tendon corrosion, department of transportation has inspected their post tension structure inventory to evaluate and quantify the pace of tendon corrosion and to estimate the rest of the lifespan from the affected member.
Infrastructure Preservation Corporation (IPC) has evolved an extensive 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 it is? While we have mentioned previously that it is a thorough tendon scanning system which works on non destructive testing principals to discover voids, water intrusion and bleeding grout in external tendons. This system includes 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 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 settle this challenge.
The actual way it is utilized? It really is a battery operated robotic system that uses the most recent in non destructive testing and modern technology. This system couples itself with all the tendon and travel along it to do a MRI like inspection of smtzmh material within it. The inspector stands on the mobile control unit which travels along with the sensor. The sensor works through wireless connectivity to transmit the collected data. The information is transferred to control station for live assessment in the tendon condition. The picture of internal portion of tendon is then 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 does it solve? This post stressed anchor helps in 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 repair or replace a post tension tendon.