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 ahead of the concrete is put.” Post tension cables in effect let us safely build large concrete structures. They enable 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, on and off ramps. These tendons have the ability to build structures that might not otherwise be possible. 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 will stand large increases in loads bearing up the concrete.
There are lots of benefits which are gained simply by using a post-tensioned approach. It enables flexibility of design, faster construction and reduce material costs. Over the long term, it can reduce maintenance costs and allow for increased loads over time.
Bridges that utilize post tension tendons can contain long and clear spans, have few beams and slender members and thinner slabs can be utilized that is unachievable in case of regular bridges. This process reinforces or strengthens the concrete or some other material with higher strength steel bar or strand which is called “tendons”. It significantly reduces the building weight and foundation load which is very useful in seismic areas.
Post tension tendons assist in construction of wedge anchor which has specific geometry requirements such as complex curves and super elevation. Extremely long span bridges can be constructed with the help of post tension tendons. Such architectures functions effectively without disrupting the traffic moving under it and also reduces the effect on environment significantly.
Post tension tendons are made from prestressing strand, anchorage, ducts, and grout and corrosion protection materials. As this technology is 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 substantial 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 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 may find corrosion and section loss inside a PT tendon.
What it is? While we have mentioned previously that it is an extensive 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 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 based 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 now have developed this TendonScan system to solve this problem.
The actual way it is used? It really is a battery operated robotic system that utilizes the newest in non destructive testing and modern technology. This method 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 together with the sensor. The sensor works through wireless connectivity to transmit the collected data. The details are moved to control station for real-time assessment of the tendon condition. The image of internal section of tendon will then be illustrated in 3D color graphics in order that any discontinuity like water intrusion, void or bleeding grout may be identified and quantified easily.
What problem does it solve? This barrel and wedge anchor works well for locating corrosion, voids, bleeding grout, section loss along with other problems in and out of the tendon. Moreover, it may also help in monitoring the discontinuities over a period of time which will help in deciding that if to fix or replace a post tension tendon.