SENTINEL^SM

To facilitate the implementation of the SENTINEL^SM solution, we are providing a few suggestions on how to effectively and efficiently deploy LifeSpan’s Dual Channel PeakStrain^TM sensors. With the purchase of a Sensor Kit and training, the core of our SENTINEL^SM solution, we offer three purchasing options to fit your budget and training needs with a written proposal.

Off-system bridges, on the cusp of a posting decisions, often create a dilemma for State DOT bridge engineers and bridge owners – using subjective visual inspection results, coupled with very conservative theoretical performance assumptions – to make a posting decision with real life consequences.

This dilemma isn’t caused by the inspectors’ subjective judgment or the engineer’s prescriptive calculations; no one is at fault for following prescribed protocols.  However, the SENTINEL^SM solution will reduce the impact of subjective judgments and overly conservative calculations by informing more objective, accurate decisions to enhance safety and reduce owner costs. It’s the captured SENTINEL^SM data that makes the difference.

LifeSpan Technologies’ low-cost SENTINEL^SM solution closes the objective data gap since it can easily be used before an inspection crew arrives, primarily for off-system bridges that make up the bulk of any State’s inventory, e.g. single or multi-span bridges, culverts, or similar low-volume crossings.

 

First Solution

 

The first and most impactful SENTINEL^SM solution applies to the concrete or steel superstructure on a bridge previously downgraded to fair, but especially after being downgraded to poor.  A lowered rating can often result in a restrictive load posting decision.  Additionally, if the bridge is currently posted, but suspected of having additional reserve load carrying capacity than its current posting, the SENTINEL^SM solution can also be used most effectively.

The obvious option to implement a SENTINEL^SM solution is to install Dual Channel PeakStrain^TM sensors at the midpoint of key superstructure members thirty to sixty days before a scheduled NBIS inspection.  With a LifeSpan Sensor Kit and training, this option will only take a few hours.

After sensor installation, the “no load” baseline sensor data is saved in a calibration spreadsheet using LifeSpan’s Hand-Held Reader.  No external power, no wired data infrastructure is required; just a few sensors that passively capture and retain the maximum strain generated by actual live loads over that time period.  Sensor temperature compensation adjustments are not necessary.

When the inspection team arrives, each of the sensors can be read in minutes with the Hand-Held Reader and that measured field data then becomes a part of the inspection record. Not a replacement for the NBIS visual condition assessment, but a second, objective input State DOT engineers can use to decide if a posting analysis is necessary or an expensive AASHTO MBE load test should be recommended.  Based on results we have seen for over 15 years, there is a very good chance any further, costly actions with regard to restrictive load postings will be avoided.

 

Second Solution

 

A second SENTINEL^SM deployment solution is to install LifeSpan’s Dual Channel PeakStrain^TM sensors over existing cracks in key superstructure members.  This can be done at any time and stay in place for as long as desired to monitor crack behavior, e.g. is the crack widening or propagating?  Opening or closing of cracks can be driven by temperature changes, but if the crack continues to widen or propagate, that is a clear warning worth further investigation.

 

Third Solution

 

A third SENTINEL^SM deployment solution is to use our Dual Channel PeakStrain^TM sensors to capture minor linear displacements, e.g. are the bridge bearings working as intended or are certain superstructure members moving from their previous positions? These concerns add risk for bridge management and knowing is always better than assuming or guesstimating.  Bearings that are not working as designed add unanticipated stress to the bridge system, possibly leading to conditions affecting the bridge’s ability to safely carry normal, or worse, heavy permit loads.

Sensor installation is simple enough that local owner technical staff can install directly, with training available in whatever format fits your program; a written training manual with photos, virtual instruction, or on-site training for agencies that prefer it.  The captured data holds up under scrutiny as LifeSpan’s Dual Channel PeakStrain^TM sensors have a history of supporting decisions to remove or relax postings that subjective, conservative protocols previously put in place. Those decisions are reviewed and approved by the State DOTs involved and are fully compliant with AASHTO’s MBE load testing protocol.  Independent references are available upon request.

 

Fourth Solution

 

A fourth highly productive SENTINEL^SM related solution is to use LifeSpan’s Sensor Kit to conduct load testing per AASHTO’s MBE protocol.  Such testing is easy to implement by local or regional engineering firms on behalf of bridge owners. The confirmed success of this process, relaxing or removing overly-severe postings, is over 60%.  We are aware of a Western State DOT that used LifeSpan’s Sensor Kits to load test twenty short span bridges that were expected to have load restrictions.  Nineteen of the twenty bridges that were load tested avoided load restrictions.

 

 

For further information and/or a procurement proposal, please contact LifeSpan Technologies at 770-234-9494 or email LifeSpan’s President and CEO at: pvanderzee@lifespantechnologies.com .