Performing A Better Bridge Inspection
NDE & NDT Technologies Advance Infrastructure InspectionsMay 11th, 2016 Author: Doug Thaler
Non Destructive Testing NDT or Non Destructive Evaluations (NDE) are best known in the medical industry with gains in the medical industries use of X-Ray and MRI’s. NDT and NDE is also used in shipping,railroads, aviation, Auto, the oil industry and NASA to look at material flaws that can prevent plane crashes, reactors to fail, pipelines to break and trains to derail.
Conducting NDE tests with non destructive testing allow the materials that are being tested to be returned and used after the tests are completed. In other words by using NDT techniques the materials that are being inspected can be returned and used by their owners after the NDT inspection. The term NDE or Non destructive evaluation although many times used interchangeably with NDT speaks more towards the actual type of test or evaluation to be performed. An NDE test will evaluate the physical characteristics or the properties of a material, locating or looking for a specific defect, like a crack, its size and shape, density of a material, durability or toughness.
IPC focuses on worldwide Infrastructures and advancing NDT & NDE techniques, technology and the reporting methodology to advance the infrastructure inspection industry. This can be bridge inspections, road and highway inspections, high mast light pole inspections, dams, tunnels, ports & more. It is amazing that currently many of the guidelines to test our structures are 25- 40 years old, still written into law and required by the D.O.T. and yet they are subjective in nature. By being subjective differing results would be provided by different inspectors with each and every inspection and inspector. This makes it difficult for the D.O. T. an asset manager or government to assess the actual damage or deterioration to a structure,manage repairs or maintain a prioritized maintenance schedule. IPC focuses on NDT and NDE technologies that provide quantitative results that show where damage is and in many cases how urgent the repairs are. IPC’s proprietary assessment reports clearly explain and assess the asset being inspected.
For example concrete bridge crack tests are conducted with each inspection cycle. A subjective test would send an inspector to a bridge typically place them in a boom truck while closing the lane down to traffic. The inspector would look at the bridge and hold a small caliper up to measure bridge cracks while poised in a bucket over traffic, sometime at night and be expected to provide accurate results.
IPC utilizes a proprietary bridge crack inspection system that can detect bridge cracks from over 1000 feet away. Not only are no lane closures or boom trucks required but the difference in a double blind test are staggering. Recently in one 200 foot bridge the inspection company utilizing conventional testing methods found no cracks in the bridge. IPC found over a dozen cracks, some of these over 3 feet long and all of them larger in width than the minimum width required by the federal government to be recorded. The old way of conducting these inspections need to change. The use of modern equipment and testing methods need to be adopted.
Infrastructure Preservation Corporation Concrete Crack
GPR Ground Penetrating Radar In Bridge deck inspections, engineering firms and asset managers are required to use a 40year old method of dragging a metal chain
across a roads deck to listen for changes in the sound that would alert an inspector to delamination or defects. Do you think that perhaps this method is outdated? I would bet that a dozen inspectors would report ten different results.
Infrastructure Preservation Corporation would recommend using their custom configured ground penetrating radar, GPR. Not only is it a non subjective inspection but you can see through the concrete and record voids and delamination that can cause serious deterioration or result in catastrophe. GPR can also be used to see rebar placement or lack thereof, calculate load ratings and pinpoint areas of concern.
Another inspection example is the inspection of post tension cables in segmental roadways and bridges. Currently inspectors are sent out to visually look for problem areas and then tap a hammer on the tendon to listen for differences that may alert the inspector to changes inside the cable. These post tension cables hold up the bridges and roadways and are too important to our infrastructure and the publics safety to conduct visual inspections. IPC
has developed proprietary and patented technology that can see through a post tension cable almost like an MRI and can locate voids, water and bleeding grout which over time would lead to corrosion. If an area of concern is found with todays visual testing method, the engineer will locate a problem area and then bore a hole in the suspect area to further investigate and issue within the cable. Once the inspection is completed the hole is filled with ground and sealed. This method has already exposed the inside of the cable and metal inside the tendon to air and moisture, which will quicken the rate of corrosion and deterioration.
IPC is fighting an uphill battle to introduce modern inspection methods for infrastructure testing and to properly utilize Non destruct testing methods to conduct non destructive evaluations that will not only help extend the life of our vital infrastructure assets, saving millions in replacement costs, but also find areas of concern early enough to make needed repairs to help ensure integrity of the structure and the publics safety.