Post Tensioned Tendon inspections

Bridges are valuable transportation assets utilized on daily basis. This makes the maintenance of the bridge more essential and significant. Since they are exposed to weather and temperature changes, they become prone to damages like corrosion, cracks etc. A neglected defect on an infrastructure like a bridge may turn out to be dangerous if not identified and repaired on time.

The construction of the bridge is done with utmost care by setting guidelines for materials and construction procedures by professional engineers and craftment. Long lasting material like concrete and steel are used in bridge construction worldwide. To prevent concrete from cracking and collapsing under a load Post-Tension tendons areused to reinforce the concrete.  With the use of post tensioning bridges can be built with less concrete and better withstand the test of time. The advantages of PT concrete have enabled us to build magnificent structures like hi rise buildings and massive bridges. These tendons just like all infrastructure assets need to be properly inspected and maintained to insure the structures safety.

Why are Post Tension tendon inspections important?

To keep the tendons free from damages like corrosion, they are placed in ducts made of plastic or galvanized steel. After the installation of the components and tensioning of the tendons, the ducts are filled with cement grout. However, because of the grout, the ducts are not completely sealed. This makes the ducts prone to crack and corrosion which allows the moisture and air to reach the steel tendons and cause corrosion. Metal loss through this process may make the whole infrastructure weak if not repaired on time. Therefore, the post-tension tendon inspection is of utmost necessity to locate such damages and fix them before any mishap.

What happens during the Post tension tendon inspection?

Till now post tension tendon inspections consisted of a visual inspection with an inspector walking under the bridge with a flashlight looking at the tendon.  In some cases a process called sounding is used. This is where the inspector hits the tendon with a hammer and listens for changes in the sound. Both of these inspection types are subjective and will vary from inspector to inspector. A company in Florida Infrastructure Preservation Corporation “IPC” is changing all of that. A robotic engineering and bridge inspection company, IPC has developed a robotic magnetic flux leakage device that can in effect peer through the concrete and outer wrapping to inspect the steel for section loss and corrosion. The tendon inspection guarantees quantitative data that allows the bridge owner, department of transportation to properly allocate their assets in order to conduct repairs according to importance. The condition assessment report will then be provided that allows repairs to be made to the right area extending the service life of the structure and keeping the public safe.

Infrastructure Preservation Corporation (IPC) offers this service within the department of transportation’s current maintenance budget. Whether you require baseline condition assessment, healthy tendon monitoring or locating corrosion, IPC can provide a complete quantitative post tension tendon inspection with detailed quantitative results unmatched in the industry today.

To know more about our services, you can log on to our website http://www.infrastructurepc.com/  or email us at info@infrastructurepc.com. You can also get a free estimate of our services by providing your details. IPC is a professional services bridge inspection and robotic engineering company providing nondestructive testing services at the same rates as current manual inspections. Their goal is to have the industry do away with subjective inspections by using modern technology and techniques to provide real quantitative data to the department of transportation.

Role of post tensioning in construction of efficient infrastructures

With the advancement in science, our world is evolving and so does the infrastructure. The demand of smart infrastructure has increased in recent decades which demand an upgraded quality of concrete so that the structure can support any load beyond its own dead weight. Many structures have collapsed in past because

• The concrete structure couldn’t bear the oversized load e.g. I-5 Skagit River Bridge accident in 2013

• It was structurally too rigid to withstand the damaging factors like strong winds e.g. I-35W Mississippi River Bridge collapse in 2007

• Frequent accidents where vehicles hit the supporting post like boat colliding with the foundation of the bridge e.g. 14th Street Bridge accident in 1982

• Design errors and material used in the construction e.g. Tacoma Narrows Bridge accident in 1940.

• Earthquakes causing damage to the structure e.g. San Francisco – Oakland Bay Bridge collapse in 1989

We have learned from these accidents that if the design and construction quality of any infrastructure is improved then accidents like bridge failures can be prevented. Post tensioning technique which uses prestressed post tensioned tendons to reinforce concrete structures has revolutionized the construction of infrastructures.  it offers many advantages over regular construction technique. Some of the features of post tensioning are following as

• It offers flexibility to the structure means if the structure tend to sag or deflect under the live load then also the concrete structure won’t crack.

• It has lowered down the material and maintenance cost

• It has also reduced the construction time because it allows longer spans in a structure without building supports.

• It increases the tensile strength and load bearing capacity of the structure thus making it durable and long lasting.

• It can also resist the environmental factors e.g. it can withstand stronger winds or earthquakes as it is structurally flexible.

How post tensioning improves the quality of concrete?

Post tension tendons made from high tensile steel, carbon fibre or aramid fibre is placed within or adjacent to concrete volume to provide flexibility to the concrete structure. When extra pressure is applied by the living load, the post tension tendons share the load and prevent cracking in the concrete member.

Once the concrete is stressed along with tendons, it becomes high strength concrete and can withstand tension forces. Post tension tendons and prestressed concrete is widely used in building huge structures like bridges, skyscrapers, dams, silos and tanks, nuclear containment structures and industrial pavement etc. Prestressed concrete with post tension tendons is much better option than the reinforced concrete because of its improved performance which allows reduced structural thickness and longer span which is essential for building complex structures.

What is the constraint while using post tension tendon in concrete structures?

The biggest advantage of post tensioning is lack of cracking and ability to span large spaces without any support. Post tension slabs can be placed or stamped just like reinforced concrete slab and the surface can be overlaid or stained. It is important to consider that the post tensioned concrete should not be cut or drilled because once a post tension tendon is cut down, it is difficult to repair or replace.

It is very difficult to find any damage to the post tension tendons from the surface as they are deeply embedded inside the concrete member. Infrastructure Preservation Corporation (IPC) provides the first post tension tendon scanning system which utilizes the Electrical Capacitance Tomography (ECT) to perform a MRI like assessment of the post tension tendons. This system is referred as “TendonScan” and it can provide accurate information about any deterioration or section loss like corrosions, voids, bleeding grout and any other problem caused to the tendons so that the decision makers can take appropriate action for repairs, in budget and on time.

To know more about TendonScan, our other products and services, you can visit our website https://www.infrastructurepc.com/ or contact us at info@infrastructurepc.com.

Overview of ipc Services

Designed to make infrastructure inspections more comprehensive and do away with lane closures,bucket trucks lifts (that delay traffic and cause accidents), perform daytime inspections and are less costly. IPC is focused on transportation infrastructure including bridge inspections and high mast light pole inspections.

Infrastructure Preservation Corporation has 6 primary services that include bridge inspections and high mast light pole inspections. Some of the inspection services are listed below.

CableScan® Cablescan® is a robotic device that ascends and descends Bridge Cablestays taking high definition videos & stills. It has the ability to maneuver around the grout ports on a cable if any.

There is a ground station that allows the inspector to see all four quadrants of the cable.  It can stop at any point and take detailed photos 30mp stills.  A Lidar attachment can get length width and depth of any anomaly’s .  Its meant to be operated in the daytime without lane closures or bucket trucks. It also measures the location on the cable stay that the issue is and where along the ground so if a bucket truck is required the exact location to park the repair truck is available.

Polescan® is a robotic device that ascends and descends a high mast light pole. PoleScan® takes hd video of the entire pole. Also stops if any issues are found and takes hd photos. The pole, seams and luminaries are all inspected with much greater detail than ever before.

Tendonscan® Tendonscan® inspects external tendons within box girders and the bridge tendons that hold up many of our nations bridges. TendonScan® identifies corrosion within the tendon to .1 percent. It’s a 2 part product. One is a device that goes around a tendon and can manually or robotically climb the tendon and locates the pre-cursors to corrosion, air, water and bleeding grout. The second device specifically locates section loss or corrosion.

Crackscan is a laser device that detects cracks in concrete and steel structures. CrackScan® can be used underneath box girders, slabs or from a distance. CrackScan® can locate cracks down to .005 from a distance of  100 feet away. The idea is for the inspection to be conducted during the day from the shoulder of the road.  No lane closures, nighttime inspections or boom trucks required. Takes less time and has been proven much more accurate than the current manual inspection process.

Bridgescan is another service that we have. It is a full bridge deck deterioration assessment.. BridgeScan® is meant to replace the chain dragging and provide a complete bridge deck and bridge approach way inspection. The inspection is so different from current methods that  it is patented.  The service utilizes ground penetrating radar / magnetics as part of the technology but takes bridge deck and bridge deck apporachway inspections to a whole new level.

ColumnScan® inspects the columns of a complex bridge. Where currently a manu is lowered from the surface with oxygen and visually looks for problems, ColumnScan® provides a whole new level of quantitative data.. It enters the columns of large segmental structures, decends down with extending and reticulating arms, high definition cameras and infrared allow for a complete inspection of the columns.with definition never seen before.

Each one of our inspections includes a comprehensive professional services assessment and can be signed and sealed by us depending on the state and their requirement.

For more information contact Doug Thaler at 727-372-2900 ext.24 or email info@infrastructurepc.com