Post tensioning is actually 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 placed.” Post tension cables essentially allow us to safely build large concrete constructions. They enable 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 and off ramps. These tendons have the ability to develop structures that may not otherwise be feasible. Because concrete is not bendable it may crack under loads. Although rebar can be used to reinforce the concrete to stop 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 that are gained by using a post-tensioned approach. It provides for flexibility of design, faster construction and lower material costs. In the long run, it could reduce maintenance costs and enable for increased loads as time passes.
Bridges that utilize post tension tendons can contain long and clear spans, have few beams and slender members and thinner slabs can be utilized which is unachievable in the event of regular bridges. This method reinforces or strengthens the concrete or other material with high strength steel bar or strand which is known as “tendons”. It significantly decreases the building weight and foundation load which can be very useful in seismic areas.
Post tension tendons aid in construction of dead-end anchorage which includes specific geometry requirements like complex curves and super elevation. Extremely long span bridges may be constructed through 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 created from prestressing strand, anchorage, ducts, and grout and corrosion protection materials. Because 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 grown to be a significant problem.
Once you have information about tendon corrosion, department of transportation has inspected their post tension structure inventory to gauge and quantify the speed of tendon corrosion as well as estimate the rest of the lifespan from the affected member.
Infrastructure Preservation Corporation (IPC) has developed an extensive 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 exactly it is? As we have mentioned previously 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 method comes with a product to detect section loss in the tendon.
Why was it developed? During construction of complex bridges, tendons are completed grout to stop corrosion. But during grouting process, the grout is likely 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 susceptible to corrosion. Complex bridge inspection is incomplete without tendon testing therefore we now have developed this TendonScan system to solve this issue.
The actual way it is utilized? This is a battery operated robotic system which uses 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 within it. The inspector stands on the mobile control unit which travels combined with the sensor. The sensor works through wireless connectivity to send out the collected data. The details are transferred to control station for live assessment from the tendon condition. The image of internal part of tendon is then illustrated in 3D color graphics so that any discontinuity like water intrusion, void or bleeding grout could be identified and quantified easily.
What problem will it solve? This barrel and wedge anchor works well for locating corrosion, voids, bleeding grout, section loss and other problems outside and inside the tendon. Moreover, it can also help in monitoring the discontinuities over a period of time which helps in deciding that whenever to correct or replace a post tension tendon.