Post tensioning is actually 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 allow us to safely build large concrete structures. They allow larger spans, thinner slabs and greater distances between support commons. Post tensioning is used in bridges and box girder structures worldwide including on our bridges, on / off ramps. These tendons make it possible to develop structures that might not otherwise be feasible. Because concrete is not flexible it can 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 can stand large increases in loads bearing up the concrete.
There are numerous benefits that are gained by using a post-tensioned approach. It provides for flexibility of design, faster construction and minimize material costs. Over the long term, it may reduce maintenance costs and enable for increased loads over time.
Bridges that utilize post tension tendons have the ability to contain long and clear spans, have few beams and slender members and thinner slabs may be used which can be difficult in the case of regular bridges. This method reinforces or strengthens the concrete or any other material rich in strength steel bar or strand which is known as “tendons”. It significantly decreases the building weight and foundation load which is very useful in seismic areas.
Post tension tendons assist in construction of anchorage grip that has specific geometry requirements like complex curves and super elevation. Extremely long span bridges could be constructed with the aid of post tension tendons. Such architectures functions effectively without disrupting the traffic moving under it and also cuts down on the impact on environment significantly.
Post tension tendons are made from 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 have become an important problem.
After getting details about tendon corrosion, department of transportation has inspected their post tension structure inventory to assess and quantify the pace of tendon corrosion and also to estimate the rest of the lifespan of 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 may find corrosion and section loss inside a PT tendon.
What exactly it is? Since we have stated earlier that it must be a comprehensive tendon scanning system which works on non destructive testing principals to learn voids, water intrusion and bleeding grout in external tendons. This technique includes a device 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 is likely 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 vunerable to corrosion. Complex bridge inspection is incomplete without tendon testing therefore we have now developed this TendonScan system to settle this challenge.
The way it can be used? This is a battery operated robotic system which uses the most recent in non destructive testing and modern technology. This method couples itself using the tendon and travel along it to do a MRI like inspection of smtzmh material inside it. The inspector stands on the mobile control unit which travels together 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 image 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 may be identified and quantified easily.
What problem can it solve? This barrel and wedge anchor helps with locating corrosion, voids, bleeding grout, section loss as well as other problems outside and inside the tendon. Moreover, it also helps in monitoring the discontinuities during a period of time which helps in deciding that if to repair or replace a post tension tendon.