Post tensioning is actually a technique for reinforcing concrete. Post-tensioning tendons is Post Tension Anchor inside plastic ducts or sleeves, are positioned in the forms before the concrete is put.” Post tension cables ultimately permit us to safely build large concrete constructions. They allow larger spans, thinner slabs and greater distances between support commons. Post tensioning is used in bridges and box girder structures around the world such as on our bridges, on and off ramps. These tendons make it possible to build structures that might not otherwise be feasible. Because concrete is not flexible it may crack under loads. Although rebar is used to strengthen the concrete to avoid 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 lots of benefits which are gained by using a post-tensioned approach. It allows for flexibility of design, faster construction and minimize material costs. In the long run, it could reduce maintenance costs and allow 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 can be difficult in the case of regular bridges. This technique reinforces or strengthens the concrete or some other material rich in strength steel bar or strand which is called “tendons”. It significantly cuts down on the building weight and foundation load which can be very beneficial in seismic areas.
Post tension tendons aid in construction of post tension anchorage which has specific geometry requirements such as complex curves and super elevation. Extremely long span bridges may be constructed with the help of post tension tendons. Such architectures functions effectively without disrupting the traffic moving under it as well as cuts down on 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 completely new therefore you will 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.
After getting information about tendon corrosion, department of transportation has inspected their post tension structure inventory to gauge and quantify the rate of tendon corrosion and to estimate the other lifespan of the affected member.
Infrastructure Preservation Corporation (IPC) has created an extensive post tension tendon inspection service named “TendonScan®” which utilizes non destructive testing and evaluation methods that may find corrosion and section loss in a PT tendon.
What it is? Since we have mentioned above that it must be an extensive tendon scanning system which works on non destructive testing principals to find out voids, water intrusion and bleeding grout in external tendons. This technique includes a device to detect section loss inside the tendon.
Why was it developed? During construction of complex bridges, tendons are completed grout to stop corrosion. But during grouting process, the grout tends 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 vunerable to corrosion. Complex bridge inspection is incomplete without tendon testing therefore we have developed this TendonScan system to resolve this problem.
The way it is used? It is a battery operated robotic system that utilizes the latest in non destructive testing and modern technology. This system couples itself with 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 together with the sensor. The sensor works through wireless connectivity to deliver the collected data. The details are moved to control station for real time assessment in the tendon condition. The picture of internal portion of tendon will be illustrated in 3D color graphics so that any discontinuity like water intrusion, void or bleeding grout can be identified and quantified easily.
What problem does it solve? This slab steel anchor helps with 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 whenever to fix or replace a post tension tendon.