Post tensioning is actually a technique for reinforcing concrete. Post-tensioning tendons is Post Tension Anchor inside plastic ducts or sleeves, are situated in the forms prior to the concrete is placed.” Post tension cables ultimately let us safely build large concrete constructions. They permit 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, off and on ramps. These tendons have the ability to develop structures that may not otherwise be possible. Because concrete is not bendable it can crack under loads. Although rebar can be used to reinforce the concrete to avoid 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 lots of benefits which are gained by using a post-tensioned approach. It enables flexibility of design, faster construction and reduce material costs. Over time, it may reduce maintenance costs and allow for increased loads over time.
Bridges that utilize post tension tendons are able to contain long and clear spans, have few beams and slender members and thinner slabs may be used which can be unachievable in the event of regular bridges. This process reinforces or strengthens the concrete or any other material with higher strength steel bar or strand which is called “tendons”. It significantly cuts down on the building weight and foundation load which is very beneficial in seismic areas.
Post tension tendons help in construction of post tension anchorage that has specific geometry requirements including complex curves and super elevation. Extremely long span bridges can be constructed with the aid of post tension tendons. Such architectures functions effectively without disrupting the traffic moving under it and in addition decreases 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 have grown to be an important problem.
After getting information about tendon corrosion, department of transportation has inspected their post tension structure inventory to evaluate and quantify the speed 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 will find corrosion and section loss in a PT tendon.
What exactly it is? Since we have stated earlier that it must be a thorough tendon scanning system which works on non destructive testing principals to discover voids, water intrusion and bleeding grout in external tendons. This method includes a product to detect section loss in the tendon.
Why was it developed? During construction of complex bridges, tendons are completed grout to prevent corrosion. But during grouting process, the grout tends to separate depending on grout’s quality, admixtures, pumping equipment and procedures. This separation result into low pH grout at tendon points and anchorage which made these locations prone to corrosion. Complex bridge inspection is incomplete without tendon testing therefore we now have developed this TendonScan system to solve this problem.
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 method couples itself using 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 send out the collected data. The information is transferred to control station for live assessment in the tendon condition. The image of internal portion of tendon is then 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 can it solve? This barrel and wedge anchor works well for locating corrosion, voids, bleeding grout, section loss and other problems in and out of the tendon. Moreover, it also helps in monitoring the discontinuities over a period of time that helps in deciding that if to fix or replace a post tension tendon.