Bridges Supported By Post Tension Tendons Are Made Safer With Robotic Inspections

February 25 13:39 2019
Post tension tendons that hold up our nations infrastructure are ageing and deteriorating causing potential hazard on bridges and structures worldwide. Currently the standard inspection method is to look visually for issues. By the time issues can be seen, it is often too late.

“Post tensioning is a technique for reinforcing concrete. Post-tensioning tendons, which are pre-stressing steel cables inside plastic ducts or sleeves. Post tension cables in effect allow us to safely build large concrete structures. They allow larger spans, thinner slabs and greater distances between support commons. Post tension tendons are used in bridges and box girder structures worldwide.

Bridges that utilize post tension tendons are able to contain long and clear spans, have few beams, slender members and typically thinner slabs which is not possible with other construction methods. This process reinforces or strengthens the concrete or other material with high strength steel bar or strands known as “tendons”. These tendons also significantly reduce the structures weight and foundation load which is very useful in seismic areas. They are responsible for some of our most beautiful and critical infrastructure.

Post tension tendons help in construction of complex bridges 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.

Post tensioning was developed in the 1930s and became a popular building method after world war II. Recent cases of corrosion of post tension tendons in complex bridges have become a significant problem. After getting information about tendon failures, department of transportation’s started to inspect their post tension structure inventory to assess and quantify the rate of tendon corrosion and to estimate the remaining lifespan of the affected member. The current visual subjective testing currently employed is just not adequate enough to ensure a structures safety. Realizing issues were mounting the bridge owners looked for ways to inspect these tendons that were more accurate than just a visual inspection.

Over the years a number of methods have been utilized to inspect tendons including sounding, gpr, borescope and electro-magnetic. All of these worked to some degree however they were slow, time consuming and not commercially practical to properly conduct field inspections, so many structures continued with visual or passed on inspections altogether.

Earlier attempts by companies to find an inspection method using ECT (Electrical Capacitance Tomography) to locate air and water, the precursors to corrosion were not adequate to deploy on consistent basis. IPC developed their own device which proved more accurate than ECT using radion waves but quickly realized that asset owner would not make repairs if just air and water were found. The very next question would be is there corrosion. The additional cost and expense to conduct a 2nd inspection or unwrap a post tension tendon without evidence of loss of metallic area was just too much of a crap shoot.

After 6yrs of R&D at their own expense, Infrastructure Preservation Corporation developed  a portable robotic means to inspect external post tension tendons and appropriately named TendonScan®. This is the first of its kind device that provides quantitative data that can be relied on.

TendonScan® eliminates the guesswork by providing percentage section loss.   Continued inspections can show loss progression over time and the urgency for repairs.  The units are portable, lightweight, wireless and accurate.

With such a critical component of the infrastructure at stake, moving the inspection methods into the 21st century must be a priority. In order for asset owners to properly allocate budgets to the most urgent repairs, quantitative, accurate data must be sought after by the department of transportation and asset owners worldwide. TendonScan® makes that possible. 

TendonScan® peers through the concrete to determine loss of metallic area /corrosion in the steel tendon and conducts the most accurate assessment to date of post tension tendons.  Moreover, it also helps in monitoring the discontinuities over a period of time which helps in deciding when to repair or replace a post tension tendon.

TendonScan® conducts a comprehensive post tension tendon inspection service that utilizes non-destructive testing and evaluation methods that can find corrosion and section loss within a PT tendon.

To learn more about post tension tendon inspection services and the latest in transportation infrastructure inspection services, you can visit our website or contact us at [email protected]

Media Contact
Company Name: Infrastructure Preservation Corporation
Contact Person: Doug Thaler, President
Email: Send Email
Phone: 727-372-2900 ext: 24
Country: United States