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 placed.” Post tension cables essentially permit us to safely build large concrete constructions. They allow 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 build structures which may not otherwise be feasible. Because concrete is not flexible it may crack under loads. Although rebar is utilized 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 which can be gained by using a post-tensioned approach. It enables flexibility of design, faster construction and minimize material costs. In the long run, it can reduce maintenance costs and permit 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 used that is not possible in the case of regular bridges. This technique reinforces or strengthens the concrete or other material rich in strength steel bar or strand which is known as “tendons”. It significantly decreases the building weight and foundation load that is very helpful in seismic areas.
Post tension tendons assist in construction of anchorage grip which includes specific geometry requirements including complex curves and super elevation. Extremely long span bridges may be constructed with the aid of post tension tendons. Such architectures functions effectively without disrupting the traffic moving under it as well as reduces the impact 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 will find no inspection systems for tendon components. Recent cases of corrosion of post tension tendons in complex bridges are becoming an important problem.
After getting details about tendon corrosion, department of transportation has inspected their post tension structure inventory to assess and quantify the rate of tendon corrosion and also to estimate the other lifespan of 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 can find corrosion and section loss in a PT tendon.
What exactly it is? Since we have stated earlier that it is a comprehensive tendon scanning system which works on non destructive testing principals to discover voids, water intrusion and bleeding grout in external tendons. This technique also includes a device to detect section loss within the tendon.
Why was it developed? During construction of complex bridges, tendons are completed grout to stop corrosion. But during grouting process, the grout has a tendency 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 resolve this challenge.
How it is used? It is a battery operated robotic system that utilizes the most recent 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 information is transferred to control station for live assessment from the tendon condition. The image of internal part of tendon will 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 helps in locating corrosion, voids, bleeding grout, section loss as well as other problems in and out of the tendon. Moreover, it can also help in monitoring the discontinuities during a period of time which helps in deciding that whenever to correct or replace a post tension tendon.