Post tensioning is a technique for reinforcing concrete. Post-tensioning tendons is Barrel And Wedges inside plastic ducts or sleeves, are situated 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 can be used in bridges and box girder structures around the world including on our bridges, on and off ramps. These tendons have the ability to construct structures that might not be possible. Because concrete is not flexible it can crack under loads. Although rebar is utilized to reinforce the concrete to stop cracks from growing the concrete can certainly 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 numerous benefits which can be gained by using a post-tensioned approach. It allows for flexibility of design, faster construction and lower material costs. In the long run, it can reduce maintenance costs and enable 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 the event 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 that is very useful in seismic areas.
Post tension tendons help in construction of anchorage grip that has specific geometry requirements such as 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 and in addition decreases the effect on environment significantly.
Post tension tendons are made from prestressing strand, anchorage, ducts, and grout and corrosion protection materials. Since this technology is new therefore there are no inspection systems for tendon components. Recent cases of corrosion of post tension tendons in complex bridges have become a significant problem.
After getting 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 remaining 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 it is? While we have mentioned previously that it is a comprehensive tendon scanning system which works on non destructive testing principals to learn 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 stop corrosion. But during grouting process, the grout tends to separate according to 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 solve this issue.
The way it can be used? It is a battery operated robotic system which uses the most recent in non destructive testing and modern technology. This technique couples itself with 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 together with the sensor. The sensor works through wireless connectivity to send out the collected data. The details are transferred to control station for real time assessment in the tendon condition. The picture of internal portion of tendon will then be 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 will it solve? This slab steel anchor helps with 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 period of time that helps in deciding that if to fix or replace a post tension tendon.