Imaging a safer future - No 28 - October 2020

Supplement your Inspection Report

Full Surface Coverage Deficiency Maps


Inspection reports for bridges and tunnels are typically filled with data sheets and single pictures of deficiencies. While these shots can be descriptive enough to derive singular action plans, comprehensive deficiency maps of entire surfaces have proven time and again to expedite structural review. Conventional reporting tools miss out on three major points:

1. An Overview of Deficiency Occurrences and Placement With only single shots, we get a piecemeal story of the overall condition of a bridge or tunnel. We might certainly get a - feel - for the overall condition by reviewing the instances one by one, but this might cause us to jump to conclusions and miss out on systematic findings. First impressions and biases can create a reality that actually is not there, but with a full map of deficiencies over all structural surfaces, we have a greater capacity to see systematic patterns of deficiencies. Pattern cracking or lengthy individual cracks that appear over broad surfaces areas are a perfect example of deficiencies that need to be considered globally.

2. Finding Deficiencies Again in the Field This is a classic example of rework that can be avoided with a full image set. Often, field teams which return to the bridge or tunnel with a findings report in hand end up setting it aside and looking for it all over again, confused by a narrative of where the deficiency is. Or the narrative in the report is slightly off, and the team opens up a section of concrete to find no deficiency at all. These cases of human error can become predictable when working in the field.

3. Calculations for Surface Condition Evaluation and Repair Materials Getting an accurate estimate of total surface area covered by cracking, spalling, and delamination is vitally important for determining the scope of the following repair work. Also, it fuels internal analysis by providing records of deficiency condition. For example, if the full-surface image shows 250 square-foot of pattern cracking and 50 square-foot of spalling, engineers can check this against the bridge or tunnel manual and see if deterioration is progressing faster or slower than prescribed.

We urge inspectors to consider enhancing their inspection deliverables with full-surface deficiency maps to avoid the above pitfalls and impress their clients. To learn more about how this can be done, visit our past project pages for examples.

Replacement or Rehabilitation? Let Scanning Decide.

Creating the Threshold with NEXCO Technology


As many structures in the US are reaching precarious points in their lives, the question of - repair or replace - is a critical conversation that must take place, often on a case-by-case basis. With mobile and wide-area scanning capabilities, NEXCO makes this choice easier.

One approach to answering the question is setting a threshold value for deficiency coverage that, if crossed, would warrant a repair. For example, UHPC Solutions suggests that once a bridge deck is covered by over 20% delamination or spalling, it should be replaced. Whatever the threshold value is determined to be, it is challenging and laborious to actually calculate through conventional methods, given that bridge decks are open to traffic and field notes are subject to individual discretion. Mobile scanning directly satisfies this approach, because the resulting scanning data can accurately derive these area calculations without closures or detours.

Another approach is the creation of a prioritization system. Certain structures may hold greater importance to the traveling public, and they are put first on repair lists while others receive intermediate repairs. Or, structures with the highest concentration of serious deficiencies are added to the top of the lists. Either way, the condition of these high-priority structures must be easily obtainable. In theory, one would be able to pull accurate deficiency records on each bridge and look at them comparatively, but current practice does not serve this purpose. InfoBridge is perhaps the closest resource to this ideal, but it still lacks surface area calculations of deficiencies (InfoBridge is being updated with NDE data for select bridges, but not on a large scale). Mobile scanning a very fitting choice for judging priority, because a large number of structures can be imaged and analyzed in a short period of time.

Because scanning data accelerates the ability to review deficiency patterns, critical findings, and prioritization, it lends itself perfectly to the choice of - repair or replace -. With the availability of advanced imaging technology, and the expertise to rapidly return detailed maps on structural conditions, NEXCO and numerous other NDE firms are ready and willing to make this difficult choice much more manageable.

NEXCO - West USA, Inc.
8300 Boone Blvd., Suite260
Tysons Corner, VA, 22182